From 1171495c8019ee706a0bf363eb38ce3e84d6567e Mon Sep 17 00:00:00 2001 From: Mike Wang Date: Sun, 2 Jun 2024 00:17:07 +0800 Subject: [PATCH] Initial commit --- LICENSE | 674 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ README.md | 146 ++++++++++++ n4.py | 448 ++++++++++++++++++++++++++++++++++++ 3 files changed, 1268 insertions(+) create mode 100644 LICENSE create mode 100644 README.md create mode 100644 n4.py diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..e62ec04 --- /dev/null +++ b/LICENSE @@ -0,0 +1,674 @@ +GNU GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The GNU General Public License is a free, copyleft license for +software and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. By contrast, +the GNU General Public License is intended to guarantee your freedom to +share and change all versions of a program--to make sure it remains free +software for all its users. We, the Free Software Foundation, use the +GNU General Public License for most of our software; it applies also to +any other work released this way by its authors. You can apply it to +your programs, too. + + When we speak of free software, we are referring to freedom, not +price. Our General Public Licenses are designed to make sure that you +have the freedom to distribute copies of free software (and charge for +them if you wish), that you receive source code or can get it if you +want it, that you can change the software or use pieces of it in new +free programs, and that you know you can do these things. + + To protect your rights, we need to prevent others from denying you +these rights or asking you to surrender the rights. Therefore, you have +certain responsibilities if you distribute copies of the software, or if +you modify it: responsibilities to respect the freedom of others. + + For example, if you distribute copies of such a program, whether +gratis or for a fee, you must pass on to the recipients the same +freedoms that you received. You must make sure that they, too, receive +or can get the source code. And you must show them these terms so they +know their rights. + + Developers that use the GNU GPL protect your rights with two steps: +(1) assert copyright on the software, and (2) offer you this License +giving you legal permission to copy, distribute and/or modify it. + + For the developers' and authors' protection, the GPL clearly explains +that there is no warranty for this free software. For both users' and +authors' sake, the GPL requires that modified versions be marked as +changed, so that their problems will not be attributed erroneously to +authors of previous versions. + + Some devices are designed to deny users access to install or run +modified versions of the software inside them, although the manufacturer +can do so. This is fundamentally incompatible with the aim of +protecting users' freedom to change the software. The systematic +pattern of such abuse occurs in the area of products for individuals to +use, which is precisely where it is most unacceptable. Therefore, we +have designed this version of the GPL to prohibit the practice for those +products. If such problems arise substantially in other domains, we +stand ready to extend this provision to those domains in future versions +of the GPL, as needed to protect the freedom of users. + + Finally, every program is threatened constantly by software patents. +States should not allow patents to restrict development and use of +software on general-purpose computers, but in those that do, we wish to +avoid the special danger that patents applied to a free program could +make it effectively proprietary. To prevent this, the GPL assures that +patents cannot be used to render the program non-free. + + The precise terms and conditions for copying, distribution and +modification follow. + + TERMS AND CONDITIONS + + 0. Definitions. + + "This License" refers to version 3 of the GNU General Public License. + + "Copyright" also means copyright-like laws that apply to other kinds of +works, such as semiconductor masks. + + "The Program" refers to any copyrightable work licensed under this +License. Each licensee is addressed as "you". "Licensees" and +"recipients" may be individuals or organizations. + + To "modify" a work means to copy from or adapt all or part of the work +in a fashion requiring copyright permission, other than the making of an +exact copy. The resulting work is called a "modified version" of the +earlier work or a work "based on" the earlier work. + + A "covered work" means either the unmodified Program or a work based +on the Program. + + To "propagate" a work means to do anything with it that, without +permission, would make you directly or secondarily liable for +infringement under applicable copyright law, except executing it on a +computer or modifying a private copy. Propagation includes copying, +distribution (with or without modification), making available to the +public, and in some countries other activities as well. + + To "convey" a work means any kind of propagation that enables other +parties to make or receive copies. Mere interaction with a user through +a computer network, with no transfer of a copy, is not conveying. + + An interactive user interface displays "Appropriate Legal Notices" +to the extent that it includes a convenient and prominently visible +feature that (1) displays an appropriate copyright notice, and (2) +tells the user that there is no warranty for the work (except to the +extent that warranties are provided), that licensees may convey the +work under this License, and how to view a copy of this License. If +the interface presents a list of user commands or options, such as a +menu, a prominent item in the list meets this criterion. + + 1. Source Code. + + The "source code" for a work means the preferred form of the work +for making modifications to it. "Object code" means any non-source +form of a work. + + A "Standard Interface" means an interface that either is an official +standard defined by a recognized standards body, or, in the case of +interfaces specified for a particular programming language, one that +is widely used among developers working in that language. + + The "System Libraries" of an executable work include anything, other +than the work as a whole, that (a) is included in the normal form of +packaging a Major Component, but which is not part of that Major +Component, and (b) serves only to enable use of the work with that +Major Component, or to implement a Standard Interface for which an +implementation is available to the public in source code form. A +"Major Component", in this context, means a major essential component +(kernel, window system, and so on) of the specific operating system +(if any) on which the executable work runs, or a compiler used to +produce the work, or an object code interpreter used to run it. + + The "Corresponding Source" for a work in object code form means all +the source code needed to generate, install, and (for an executable +work) run the object code and to modify the work, including scripts to +control those activities. However, it does not include the work's +System Libraries, or general-purpose tools or generally available free +programs which are used unmodified in performing those activities but +which are not part of the work. For example, Corresponding Source +includes interface definition files associated with source files for +the work, and the source code for shared libraries and dynamically +linked subprograms that the work is specifically designed to require, +such as by intimate data communication or control flow between those +subprograms and other parts of the work. + + The Corresponding Source need not include anything that users +can regenerate automatically from other parts of the Corresponding +Source. + + The Corresponding Source for a work in source code form is that +same work. + + 2. Basic Permissions. + + All rights granted under this License are granted for the term of +copyright on the Program, and are irrevocable provided the stated +conditions are met. This License explicitly affirms your unlimited +permission to run the unmodified Program. The output from running a +covered work is covered by this License only if the output, given its +content, constitutes a covered work. This License acknowledges your +rights of fair use or other equivalent, as provided by copyright law. + + You may make, run and propagate covered works that you do not +convey, without conditions so long as your license otherwise remains +in force. You may convey covered works to others for the sole purpose +of having them make modifications exclusively for you, or provide you +with facilities for running those works, provided that you comply with +the terms of this License in conveying all material for which you do +not control copyright. Those thus making or running the covered works +for you must do so exclusively on your behalf, under your direction +and control, on terms that prohibit them from making any copies of +your copyrighted material outside their relationship with you. + + Conveying under any other circumstances is permitted solely under +the conditions stated below. Sublicensing is not allowed; section 10 +makes it unnecessary. + + 3. Protecting Users' Legal Rights From Anti-Circumvention Law. + + No covered work shall be deemed part of an effective technological +measure under any applicable law fulfilling obligations under article +11 of the WIPO copyright treaty adopted on 20 December 1996, or +similar laws prohibiting or restricting circumvention of such +measures. + + When you convey a covered work, you waive any legal power to forbid +circumvention of technological measures to the extent such circumvention +is effected by exercising rights under this License with respect to +the covered work, and you disclaim any intention to limit operation or +modification of the work as a means of enforcing, against the work's +users, your or third parties' legal rights to forbid circumvention of +technological measures. + + 4. Conveying Verbatim Copies. + + You may convey verbatim copies of the Program's source code as you +receive it, in any medium, provided that you conspicuously and +appropriately publish on each copy an appropriate copyright notice; +keep intact all notices stating that this License and any +non-permissive terms added in accord with section 7 apply to the code; +keep intact all notices of the absence of any warranty; and give all +recipients a copy of this License along with the Program. + + You may charge any price or no price for each copy that you convey, +and you may offer support or warranty protection for a fee. + + 5. Conveying Modified Source Versions. + + You may convey a work based on the Program, or the modifications to +produce it from the Program, in the form of source code under the +terms of section 4, provided that you also meet all of these conditions: + + a) The work must carry prominent notices stating that you modified + it, and giving a relevant date. + + b) The work must carry prominent notices stating that it is + released under this License and any conditions added under section + 7. This requirement modifies the requirement in section 4 to + "keep intact all notices". + + c) You must license the entire work, as a whole, under this + License to anyone who comes into possession of a copy. This + License will therefore apply, along with any applicable section 7 + additional terms, to the whole of the work, and all its parts, + regardless of how they are packaged. This License gives no + permission to license the work in any other way, but it does not + invalidate such permission if you have separately received it. + + d) If the work has interactive user interfaces, each must display + Appropriate Legal Notices; however, if the Program has interactive + interfaces that do not display Appropriate Legal Notices, your + work need not make them do so. + + A compilation of a covered work with other separate and independent +works, which are not by their nature extensions of the covered work, +and which are not combined with it such as to form a larger program, +in or on a volume of a storage or distribution medium, is called an +"aggregate" if the compilation and its resulting copyright are not +used to limit the access or legal rights of the compilation's users +beyond what the individual works permit. Inclusion of a covered work +in an aggregate does not cause this License to apply to the other +parts of the aggregate. + + 6. Conveying Non-Source Forms. + + You may convey a covered work in object code form under the terms +of sections 4 and 5, provided that you also convey the +machine-readable Corresponding Source under the terms of this License, +in one of these ways: + + a) Convey the object code in, or embodied in, a physical product + (including a physical distribution medium), accompanied by the + Corresponding Source fixed on a durable physical medium + customarily used for software interchange. + + b) Convey the object code in, or embodied in, a physical product + (including a physical distribution medium), accompanied by a + written offer, valid for at least three years and valid for as + long as you offer spare parts or customer support for that product + model, to give anyone who possesses the object code either (1) a + copy of the Corresponding Source for all the software in the + product that is covered by this License, on a durable physical + medium customarily used for software interchange, for a price no + more than your reasonable cost of physically performing this + conveying of source, or (2) access to copy the + Corresponding Source from a network server at no charge. + + c) Convey individual copies of the object code with a copy of the + written offer to provide the Corresponding Source. This + alternative is allowed only occasionally and noncommercially, and + only if you received the object code with such an offer, in accord + with subsection 6b. + + d) Convey the object code by offering access from a designated + place (gratis or for a charge), and offer equivalent access to the + Corresponding Source in the same way through the same place at no + further charge. You need not require recipients to copy the + Corresponding Source along with the object code. If the place to + copy the object code is a network server, the Corresponding Source + may be on a different server (operated by you or a third party) + that supports equivalent copying facilities, provided you maintain + clear directions next to the object code saying where to find the + Corresponding Source. Regardless of what server hosts the + Corresponding Source, you remain obligated to ensure that it is + available for as long as needed to satisfy these requirements. + + e) Convey the object code using peer-to-peer transmission, provided + you inform other peers where the object code and Corresponding + Source of the work are being offered to the general public at no + charge under subsection 6d. + + A separable portion of the object code, whose source code is excluded +from the Corresponding Source as a System Library, need not be +included in conveying the object code work. + + A "User Product" is either (1) a "consumer product", which means any +tangible personal property which is normally used for personal, family, +or household purposes, or (2) anything designed or sold for incorporation +into a dwelling. In determining whether a product is a consumer product, +doubtful cases shall be resolved in favor of coverage. For a particular +product received by a particular user, "normally used" refers to a +typical or common use of that class of product, regardless of the status +of the particular user or of the way in which the particular user +actually uses, or expects or is expected to use, the product. A product +is a consumer product regardless of whether the product has substantial +commercial, industrial or non-consumer uses, unless such uses represent +the only significant mode of use of the product. + + "Installation Information" for a User Product means any methods, +procedures, authorization keys, or other information required to install +and execute modified versions of a covered work in that User Product from +a modified version of its Corresponding Source. The information must +suffice to ensure that the continued functioning of the modified object +code is in no case prevented or interfered with solely because +modification has been made. + + If you convey an object code work under this section in, or with, or +specifically for use in, a User Product, and the conveying occurs as +part of a transaction in which the right of possession and use of the +User Product is transferred to the recipient in perpetuity or for a +fixed term (regardless of how the transaction is characterized), the +Corresponding Source conveyed under this section must be accompanied +by the Installation Information. But this requirement does not apply +if neither you nor any third party retains the ability to install +modified object code on the User Product (for example, the work has +been installed in ROM). + + The requirement to provide Installation Information does not include a +requirement to continue to provide support service, warranty, or updates +for a work that has been modified or installed by the recipient, or for +the User Product in which it has been modified or installed. Access to a +network may be denied when the modification itself materially and +adversely affects the operation of the network or violates the rules and +protocols for communication across the network. + + Corresponding Source conveyed, and Installation Information provided, +in accord with this section must be in a format that is publicly +documented (and with an implementation available to the public in +source code form), and must require no special password or key for +unpacking, reading or copying. + + 7. Additional Terms. + + "Additional permissions" are terms that supplement the terms of this +License by making exceptions from one or more of its conditions. +Additional permissions that are applicable to the entire Program shall +be treated as though they were included in this License, to the extent +that they are valid under applicable law. If additional permissions +apply only to part of the Program, that part may be used separately +under those permissions, but the entire Program remains governed by +this License without regard to the additional permissions. + + When you convey a copy of a covered work, you may at your option +remove any additional permissions from that copy, or from any part of +it. (Additional permissions may be written to require their own +removal in certain cases when you modify the work.) You may place +additional permissions on material, added by you to a covered work, +for which you have or can give appropriate copyright permission. + + Notwithstanding any other provision of this License, for material you +add to a covered work, you may (if authorized by the copyright holders of +that material) supplement the terms of this License with terms: + + a) Disclaiming warranty or limiting liability differently from the + terms of sections 15 and 16 of this License; or + + b) Requiring preservation of specified reasonable legal notices or + author attributions in that material or in the Appropriate Legal + Notices displayed by works containing it; or + + c) Prohibiting misrepresentation of the origin of that material, or + requiring that modified versions of such material be marked in + reasonable ways as different from the original version; or + + d) Limiting the use for publicity purposes of names of licensors or + authors of the material; or + + e) Declining to grant rights under trademark law for use of some + trade names, trademarks, or service marks; or + + f) Requiring indemnification of licensors and authors of that + material by anyone who conveys the material (or modified versions of + it) with contractual assumptions of liability to the recipient, for + any liability that these contractual assumptions directly impose on + those licensors and authors. + + All other non-permissive additional terms are considered "further +restrictions" within the meaning of section 10. If the Program as you +received it, or any part of it, contains a notice stating that it is +governed by this License along with a term that is a further +restriction, you may remove that term. If a license document contains +a further restriction but permits relicensing or conveying under this +License, you may add to a covered work material governed by the terms +of that license document, provided that the further restriction does +not survive such relicensing or conveying. + + If you add terms to a covered work in accord with this section, you +must place, in the relevant source files, a statement of the +additional terms that apply to those files, or a notice indicating +where to find the applicable terms. + + Additional terms, permissive or non-permissive, may be stated in the +form of a separately written license, or stated as exceptions; +the above requirements apply either way. + + 8. Termination. + + You may not propagate or modify a covered work except as expressly +provided under this License. Any attempt otherwise to propagate or +modify it is void, and will automatically terminate your rights under +this License (including any patent licenses granted under the third +paragraph of section 11). + + However, if you cease all violation of this License, then your +license from a particular copyright holder is reinstated (a) +provisionally, unless and until the copyright holder explicitly and +finally terminates your license, and (b) permanently, if the copyright +holder fails to notify you of the violation by some reasonable means +prior to 60 days after the cessation. + + Moreover, your license from a particular copyright holder is +reinstated permanently if the copyright holder notifies you of the +violation by some reasonable means, this is the first time you have +received notice of violation of this License (for any work) from that +copyright holder, and you cure the violation prior to 30 days after +your receipt of the notice. + + Termination of your rights under this section does not terminate the +licenses of parties who have received copies or rights from you under +this License. If your rights have been terminated and not permanently +reinstated, you do not qualify to receive new licenses for the same +material under section 10. + + 9. Acceptance Not Required for Having Copies. + + You are not required to accept this License in order to receive or +run a copy of the Program. Ancillary propagation of a covered work +occurring solely as a consequence of using peer-to-peer transmission +to receive a copy likewise does not require acceptance. However, +nothing other than this License grants you permission to propagate or +modify any covered work. These actions infringe copyright if you do +not accept this License. Therefore, by modifying or propagating a +covered work, you indicate your acceptance of this License to do so. + + 10. Automatic Licensing of Downstream Recipients. + + Each time you convey a covered work, the recipient automatically +receives a license from the original licensors, to run, modify and +propagate that work, subject to this License. You are not responsible +for enforcing compliance by third parties with this License. + + An "entity transaction" is a transaction transferring control of an +organization, or substantially all assets of one, or subdividing an +organization, or merging organizations. If propagation of a covered +work results from an entity transaction, each party to that +transaction who receives a copy of the work also receives whatever +licenses to the work the party's predecessor in interest had or could +give under the previous paragraph, plus a right to possession of the +Corresponding Source of the work from the predecessor in interest, if +the predecessor has it or can get it with reasonable efforts. + + You may not impose any further restrictions on the exercise of the +rights granted or affirmed under this License. For example, you may +not impose a license fee, royalty, or other charge for exercise of +rights granted under this License, and you may not initiate litigation +(including a cross-claim or counterclaim in a lawsuit) alleging that +any patent claim is infringed by making, using, selling, offering for +sale, or importing the Program or any portion of it. + + 11. Patents. + + A "contributor" is a copyright holder who authorizes use under this +License of the Program or a work on which the Program is based. The +work thus licensed is called the contributor's "contributor version". + + A contributor's "essential patent claims" are all patent claims +owned or controlled by the contributor, whether already acquired or +hereafter acquired, that would be infringed by some manner, permitted +by this License, of making, using, or selling its contributor version, +but do not include claims that would be infringed only as a +consequence of further modification of the contributor version. For +purposes of this definition, "control" includes the right to grant +patent sublicenses in a manner consistent with the requirements of +this License. + + Each contributor grants you a non-exclusive, worldwide, royalty-free +patent license under the contributor's essential patent claims, to +make, use, sell, offer for sale, import and otherwise run, modify and +propagate the contents of its contributor version. + + In the following three paragraphs, a "patent license" is any express +agreement or commitment, however denominated, not to enforce a patent +(such as an express permission to practice a patent or covenant not to +sue for patent infringement). To "grant" such a patent license to a +party means to make such an agreement or commitment not to enforce a +patent against the party. + + If you convey a covered work, knowingly relying on a patent license, +and the Corresponding Source of the work is not available for anyone +to copy, free of charge and under the terms of this License, through a +publicly available network server or other readily accessible means, +then you must either (1) cause the Corresponding Source to be so +available, or (2) arrange to deprive yourself of the benefit of the +patent license for this particular work, or (3) arrange, in a manner +consistent with the requirements of this License, to extend the patent +license to downstream recipients. "Knowingly relying" means you have +actual knowledge that, but for the patent license, your conveying the +covered work in a country, or your recipient's use of the covered work +in a country, would infringe one or more identifiable patents in that +country that you have reason to believe are valid. + + If, pursuant to or in connection with a single transaction or +arrangement, you convey, or propagate by procuring conveyance of, a +covered work, and grant a patent license to some of the parties +receiving the covered work authorizing them to use, propagate, modify +or convey a specific copy of the covered work, then the patent license +you grant is automatically extended to all recipients of the covered +work and works based on it. + + A patent license is "discriminatory" if it does not include within +the scope of its coverage, prohibits the exercise of, or is +conditioned on the non-exercise of one or more of the rights that are +specifically granted under this License. You may not convey a covered +work if you are a party to an arrangement with a third party that is +in the business of distributing software, under which you make payment +to the third party based on the extent of your activity of conveying +the work, and under which the third party grants, to any of the +parties who would receive the covered work from you, a discriminatory +patent license (a) in connection with copies of the covered work +conveyed by you (or copies made from those copies), or (b) primarily +for and in connection with specific products or compilations that +contain the covered work, unless you entered into that arrangement, +or that patent license was granted, prior to 28 March 2007. + + Nothing in this License shall be construed as excluding or limiting +any implied license or other defenses to infringement that may +otherwise be available to you under applicable patent law. + + 12. No Surrender of Others' Freedom. + + If conditions are imposed on you (whether by court order, agreement or +otherwise) that contradict the conditions of this License, they do not +excuse you from the conditions of this License. If you cannot convey a +covered work so as to satisfy simultaneously your obligations under this +License and any other pertinent obligations, then as a consequence you may +not convey it at all. For example, if you agree to terms that obligate you +to collect a royalty for further conveying from those to whom you convey +the Program, the only way you could satisfy both those terms and this +License would be to refrain entirely from conveying the Program. + + 13. Use with the GNU Affero General Public License. + + Notwithstanding any other provision of this License, you have +permission to link or combine any covered work with a work licensed +under version 3 of the GNU Affero General Public License into a single +combined work, and to convey the resulting work. The terms of this +License will continue to apply to the part which is the covered work, +but the special requirements of the GNU Affero General Public License, +section 13, concerning interaction through a network will apply to the +combination as such. + + 14. Revised Versions of this License. + + The Free Software Foundation may publish revised and/or new versions of +the GNU General Public License from time to time. Such new versions will +be similar in spirit to the present version, but may differ in detail to +address new problems or concerns. + + Each version is given a distinguishing version number. If the +Program specifies that a certain numbered version of the GNU General +Public License "or any later version" applies to it, you have the +option of following the terms and conditions either of that numbered +version or of any later version published by the Free Software +Foundation. If the Program does not specify a version number of the +GNU General Public License, you may choose any version ever published +by the Free Software Foundation. + + If the Program specifies that a proxy can decide which future +versions of the GNU General Public License can be used, that proxy's +public statement of acceptance of a version permanently authorizes you +to choose that version for the Program. + + Later license versions may give you additional or different +permissions. However, no additional obligations are imposed on any +author or copyright holder as a result of your choosing to follow a +later version. + + 15. Disclaimer of Warranty. + + THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY +APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT +HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY +OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, +THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR +PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM +IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF +ALL NECESSARY SERVICING, REPAIR OR CORRECTION. + + 16. Limitation of Liability. + + IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING +WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS +THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY +GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE +USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF +DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD +PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), +EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF +SUCH DAMAGES. + + 17. Interpretation of Sections 15 and 16. + + If the disclaimer of warranty and limitation of liability provided +above cannot be given local legal effect according to their terms, +reviewing courts shall apply local law that most closely approximates +an absolute waiver of all civil liability in connection with the +Program, unless a warranty or assumption of liability accompanies a +copy of the Program in return for a fee. + + END OF TERMS AND CONDITIONS + + How to Apply These Terms to Your New Programs + + If you develop a new program, and you want it to be of the greatest +possible use to the public, the best way to achieve this is to make it +free software which everyone can redistribute and change under these terms. + + To do so, attach the following notices to the program. It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + + Copyright (C) + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + Copyright (C) + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. diff --git a/README.md b/README.md new file mode 100644 index 0000000..a9cd96f --- /dev/null +++ b/README.md @@ -0,0 +1,146 @@ +# N4 + +N4 是针对双方均为 “端口递增型 NAT” 的一种打洞测试工具。 + +> “端口递增型 NAT” 不限制 NAT 种类。 +> 也就是说，即使双方均为对称型 NAT（NAT4 - NAT4），只要满足端口递增，也可使用此工具成功打通。 + + +## 快速开始 +公网服务器运行： +```bash +python3 n4.py -s +``` + +需要打洞的两个 NAT4 客户端运行： +```bash +python3 n4.py -c -h 服务器IP +``` + +客户端日志显示： + +``` +[2024-06-01 12:38:56,438] INFO [n4.py:375] ================== +[2024-06-01 12:38:56,439] INFO [n4.py:376] Source port: 30000-30025 +[2024-06-01 12:38:56,459] INFO [n4.py:287] <= Hello +[2024-06-01 12:38:56,471] INFO [n4.py:293] => Ready +[2024-06-01 12:38:56,472] INFO [n4.py:302] <= Exchange +[2024-06-01 12:38:56,486] INFO [n4.py:312] => Peer: 203.0.113.12:5793 +[2024-06-01 12:38:56,486] INFO [n4.py:313] [ Target: 203.0.113.12:5813 ] +[2024-06-01 12:38:56,487] INFO [n4.py:321] <= Punch +[2024-06-01 12:39:06,498] INFO [n4.py:386] [ LOSE ] +[2024-06-01 12:39:06,500] INFO [n4.py:375] ================== +[2024-06-01 12:39:06,500] INFO [n4.py:376] Source port: 30025-30050 +[2024-06-01 12:39:06,514] INFO [n4.py:287] <= Hello +[2024-06-01 12:39:06,526] INFO [n4.py:293] => Ready +[2024-06-01 12:39:06,527] INFO [n4.py:302] <= Exchange +[2024-06-01 12:39:06,541] INFO [n4.py:312] => Peer: 203.0.113.12:5434 +[2024-06-01 12:39:06,541] INFO [n4.py:313] [ Target: 203.0.113.12:5454 ] +[2024-06-01 12:39:06,542] INFO [n4.py:321] <= Punch +[2024-06-01 12:39:06,556] INFO [n4.py:334] => Punch from peer +[2024-06-01 12:39:08,559] INFO [n4.py:342] <= Punch +[2024-06-01 12:39:08,560] INFO [n4.py:379] ------ +[2024-06-01 12:39:08,560] INFO [n4.py:380] Local port: 30040 +[2024-06-01 12:39:08,560] INFO [n4.py:381] Peer address: 203.0.113.12:5454 +[2024-06-01 12:39:08,560] INFO [n4.py:382] ------ +[2024-06-01 12:39:08,560] INFO [n4.py:383] [ WIN ] +[2024-06-01 12:39:08,560] INFO [n4.py:385] > nc -u -p 30040 203.0.113.12 5454 +``` + +日志出现 `[ WIN ]` 字样，表示两者打通。 + +双方运行日志中提示的 `nc` 命令，即可互相进行 P2P 通信。 + + +## 打洞过程 + +服务端监听 `TCP/1721` 和 `UDP/1721`。 + +- TCP 端口用于与客户端通信； +- UDP 端口仅用于获取客户端公网上的IP、端口信息，只接收不发送。 + +打洞过程共有 5 步： +``` +1. Hello client --TCP-> server +2. Ready client <-TCP-- server +3. Exchange client --UDP-> server +4. Peerinfo client <-TCP-- server +5. Punch client <-UDP-> client +``` + +解释说明： + +1. 客户端向服务端发送 Hello 包； +2. 服务端收到两个客户端的 Hello 包后，同时向两方发送 Ready 包； +3. 客户端收到 Ready 包，使用 UDP 向服务器发送 Exchange 包，表示交换两客户端 UDP 公网信息； +4. 服务端收到一客户端的 Exchange 包，向另一客户端发送 Peerinfo 包，携带前者 UDP 公网信息； +5. 客户端收到 Peerinfo 包，根据对方地址 `IP:PORT`， + 预测对方将来的地址会有 `IP:PORT + peer_port_offset`。 + 客户端从自身端口 `src_port_start` ~ `src_port_start + src_port_count` 范围， + 使用 UDP 逐一向 `IP:PORT + peer_port_offset` 固定地址发送 Punch 包。 + +如果客户端收到 Punch 包，代表打通。否则，增加源端口值，再次尝试。 + + +## 示例说明 + +下面是一个示例，假设有以下设定值。 + +``` +src_port_start = 30000 +src_port_count = 8 +peer_port_offset = 5 +``` + +括号内为 NAT 转换后的地址。该地址只对目标可见，对来源不可见。 + +客户端A： + +``` +---(Exchange)--- +192.168.1.101:30000 --> (198.51.100.3:1801) --> 192.0.2.2:1721 +----(Punch)----- +192.168.1.101:30000 --> (198.51.100.3:1803) --> 203.0.113.12:3028 +192.168.1.101:30001 --> (198.51.100.3:1804) --> 203.0.113.12:3028 +192.168.1.101:30002 --> (198.51.100.3:1807) --> 203.0.113.12:3028 +192.168.1.101:30003 --> (198.51.100.3:1806) --> 203.0.113.12:3028 [*] +192.168.1.101:30004 --> (198.51.100.3:1810) --> 203.0.113.12:3028 +192.168.1.101:30005 --> (198.51.100.3:1812) --> 203.0.113.12:3028 +192.168.1.101:30006 --> (198.51.100.3:1817) --> 203.0.113.12:3028 +192.168.1.101:30007 --> (198.51.100.3:1814) --> 203.0.113.12:3028 +``` + +客户端B： + +``` +---(Exchange)--- +192.168.0.112:30000 --> (203.0.113.19:3023) --> 192.0.2.2:1721 +----(Punch)----- +192.168.0.112:30000 --> (203.0.113.12:3025) --> 198.51.100.3:1806 +192.168.0.112:30001 --> (203.0.113.12:3029) --> 198.51.100.3:1806 +192.168.0.112:30002 --> (203.0.113.12:2030) --> 198.51.100.3:1806 +192.168.0.112:30003 --> (203.0.113.12:3031) --> 198.51.100.3:1806 +192.168.0.112:30004 --> (203.0.113.12:3028) --> 198.51.100.3:1806 [*] +192.168.0.112:30005 --> (203.0.113.12:3032) --> 198.51.100.3:1806 +192.168.0.112:30006 --> (203.0.113.12:3033) --> 198.51.100.3:1806 +192.168.0.112:30007 --> (203.0.113.12:3034) --> 198.51.100.3:1806 +``` + +在以上打洞组合中，`[*]` 标记的一对尝试，成功打通。 + +客户端 A 运行： +``` +nc -u -l 30003 +``` + +客户端 B 运行： +``` +nc -u -p 30004 198.51.100.3 1806 +``` + +两者即可 P2P 通信。 + + +## License + +GNU General Public License v3.0 diff --git a/n4.py b/n4.py new file mode 100644 index 0000000..889b6d2 --- /dev/null +++ b/n4.py @@ -0,0 +1,448 @@ +#!/usr/bin/env python3 + +from typing import Optional, Tuple, List +import argparse +import logging +import struct +import socket +import select +import time + +args = argparse.Namespace() + +logging.basicConfig( + level=logging.INFO, + format="[%(asctime)s] %(levelname)s [%(filename)s:%(lineno)d] %(message)s" +) + +class N4Error: + class InvalidPacket(Exception): + pass + class PunchFailure(Exception): + pass + +class N4Packet: + + # packet format: + # [ command (1 byte) | reserved (1 byte) | data (6 bytes) ] + + SIZE = 8 + + CMD_HELLO = 0x01 # client --TCP-> server + CMD_READY = 0x02 # client <-TCP-- server + CMD_EXCHG = 0x03 # client --UDP-> server + CMD_PINFO = 0x04 # client <-TCP-- server + CMD_PUNCH = 0x05 # client <-UDP-> client + + RESERVED = 0x00 + + @staticmethod + def hello(ident: bytes) -> bytes: + pkt = struct.pack( + "!BB6s", N4Packet.CMD_HELLO, N4Packet.RESERVED, ident + ) + return pkt + + @staticmethod + def dec_hello(pkt: bytes) -> Optional[bytes]: + if len(pkt) != N4Packet.SIZE: + return None + cmd, _, ident = struct.unpack("!BB6s", pkt) + if cmd != N4Packet.CMD_HELLO: + return None + return ident + + @staticmethod + def ready() -> bytes: + pkt = struct.pack( + "!BB6s", N4Packet.CMD_READY, N4Packet.RESERVED, b"" + ) + return pkt + + @staticmethod + def dec_ready(pkt: bytes) -> Optional[bool]: + if len(pkt) != N4Packet.SIZE: + return None + cmd, _, _ = struct.unpack("!BB6s", pkt) + if cmd != N4Packet.CMD_READY: + return None + return True + + @staticmethod + def exchange(ident: bytes) -> bytes: + pkt = struct.pack( + "!BB6s", N4Packet.CMD_EXCHG, N4Packet.RESERVED, ident + ) + return pkt + + @staticmethod + def dec_exchange(pkt: bytes) -> Optional[bytes]: + if len(pkt) != N4Packet.SIZE: + return None + cmd, _, ident = struct.unpack("!BB6s", pkt) + if cmd != N4Packet.CMD_EXCHG: + return None + return ident + + @staticmethod + def peerinfo(peeraddr: Tuple[str, int]) -> bytes: + ip, port = peeraddr + ipb = socket.inet_aton(ip) + pkt = struct.pack( + "!BB4sH", N4Packet.CMD_PINFO, N4Packet.RESERVED, ipb, port + ) + return pkt + + @staticmethod + def dec_peerinfo(pkt: bytes) -> Optional[Tuple[str, int]]: + if len(pkt) != N4Packet.SIZE: + return None + cmd, _, ipb, port = struct.unpack("!BB4sH", pkt) + if cmd != N4Packet.CMD_PINFO: + return None + ip = socket.inet_ntoa(ipb) + peeraddr = (ip, port) + return peeraddr + + @staticmethod + def punch(ident: bytes) -> Optional[bytes]: + pkt = struct.pack( + "!BB6s", N4Packet.CMD_PUNCH, N4Packet.RESERVED, ident + ) + return pkt + + @staticmethod + def dec_punch(pkt: bytes) -> Optional[bytes]: + if len(pkt) != N4Packet.SIZE: + return None + cmd, _, ident = struct.unpack("!BB6s", pkt) + if cmd != N4Packet.CMD_PUNCH: + return None + return ident + + +class N4Server: + ident : bytes + bind_port : int + sock : Optional[socket.socket] + usock : Optional[socket.socket] + conn : List[socket.socket] + + def __init__(self, ident: bytes, bind_port: int) -> None: + self.ident = ident + self.bind_port = bind_port + self.sock = None + self.usock = None + self.conn = [] + + def _init_sock(self) -> None: + self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) + if hasattr(socket, "SO_REUSEADDR"): + self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + if hasattr(socket, "SO_REUSEPORT"): + self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1) + self.sock.bind(("0.0.0.0", self.bind_port)) + self.sock.listen(5) + + self.usock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) + if hasattr(socket, "SO_REUSEADDR"): + self.usock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + if hasattr(socket, "SO_REUSEPORT"): + self.usock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1) + self.usock.bind(("0.0.0.0", self.bind_port)) + + logging.info("Listening on TCP/%d and UDP/%d" % (self.bind_port, self.bind_port)) + + def _close_all_sock(self) -> None: + if self.sock: + self.sock.close() + + if self.usock: + self.usock.close() + + while self.conn: + s = self.conn.pop() + s.close() + + def _clear_usock_buff(self) -> None: + while True: + r, w, x = select.select([self.usock], [], [], 0) + if not r: + return + self.usock.recvfrom(0xffff) + + @staticmethod + def _sock_same_peer_ip(sock, addr): + return sock.getpeername()[0] == addr[0] + + def _wait_client(self) -> None: + while len(self.conn) < 2: + c, addr = self.sock.accept() + logging.info("New connection: %s:%d" % (addr[0], addr[1])) + try: + r, w, x = select.select([c], [], [], 60) + if r: + hello_pkt = r[0].recv(N4Packet.SIZE) + recv_ident = N4Packet.dec_hello(hello_pkt) + if not recv_ident: + raise N4Error.InvalidPacket("Invalid packet from N4 Client") + if recv_ident == self.ident: + self.conn.append(r[0]) + else: + logging.info("Identifier mismatch. Ignored.") + except Exception as e: + logging.error(e) + finally: + if c not in self.conn: + c.close() + + def serve(self) -> None: + self._init_sock() + self._wait_client() + self._clear_usock_buff() + + ready_pkt = N4Packet.ready() + self.conn[0].send(ready_pkt) + self.conn[1].send(ready_pkt) + ok1 = ok2 = False + try: + while True: + exchg_pkt, addr = self.usock.recvfrom(0xffff) + recv_ident = N4Packet.dec_exchange(exchg_pkt) + if not recv_ident: + raise N4Error.InvalidPacket("Invalid packet from N4 Client") + if recv_ident != self.ident: + continue + + if not ok1 and self._sock_same_peer_ip(self.conn[0], addr): + pinfo_pkt = N4Packet.peerinfo(addr) + self.conn[1].send(pinfo_pkt) + ok1 = True + elif not ok2 and self._sock_same_peer_ip(self.conn[1], addr): + pinfo_pkt = N4Packet.peerinfo(addr) + self.conn[0].send(pinfo_pkt) + ok2 = True + if ok1 and ok2: + break + except Exception as ex: + logging.error(ex) + finally: + self._clear_usock_buff() + self._close_all_sock() + + +class N4Client: + ident : bytes + server_host : str + server_port : int + src_port_start : int + src_port_count : int + peer_port_offset : int + sock : Optional[socket.socket] + pool : List[socket.socket] + + def __init__(self, + ident: bytes, + server_host: str, server_port: int, + src_port_start: int, src_port_count: int, + peer_port_offset: int) -> None: + self.ident = ident + self.server_host = server_host + self.server_port = server_port + self.src_port_start = src_port_start + self.src_port_count = src_port_count + self.peer_port_offset = peer_port_offset + self.sock = None + self.pool = [] + + def _init_sock(self) -> None: + self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) + self.sock.connect((self.server_host, self.server_port)) + for i in range(self.src_port_count): + port = 0 + if self.src_port_start: + port = self.src_port_start + i + sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) + if hasattr(socket, "SO_REUSEADDR"): + sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) + if hasattr(socket, "SO_REUSEPORT"): + sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1) + sock.bind(("0.0.0.0", port)) + self.pool.append(sock) + + def _close_all_sock(self) -> None: + if self.sock: + self.sock.close() + + while self.pool: + s = self.pool.pop() + s.close() + + def punch(self, wait: int) -> Tuple[Tuple[str, int], int]: + self._init_sock() + + hello_pkt = N4Packet.hello(self.ident) + self.sock.send(hello_pkt) + + logging.info(" <= Hello ") + + ready_pkt = self.sock.recv(N4Packet.SIZE) + if not N4Packet.dec_ready(ready_pkt): + raise N4Error.InvalidPacket("Invalid packet from N4 Server") + + logging.info(" => Ready ") + + exchg_pkt = N4Packet.exchange(self.ident) + # send three times to avoid packet loss + for _ in range(3): + self.pool[0].sendto( + exchg_pkt, (self.server_host, self.server_port) + ) + + logging.info(" <= Exchange ") + + pinfo_pkt = self.sock.recv(N4Packet.SIZE) + peer = N4Packet.dec_peerinfo(pinfo_pkt) + if not peer: + raise N4Error.InvalidPacket("Invalid packet from N4 Server") + + peer_ip, peer_port = peer + target = (peer_ip, peer_port + self.peer_port_offset) + + logging.info(" => Peer: %s:%d " % peer) + logging.info(" [ Target: %s:%d ] " % target) + + punch_pkt = N4Packet.punch(self.ident) + # repeat five times to avoid packet loss + for _ in range(5): + for sock in self.pool: + sock.sendto(punch_pkt, target) + + logging.info(" <= Punch ") + + etime = time.time() + wait + while True: + r, w, x = select.select(self.pool, [], [], etime-time.time()) + if not r: + self._close_all_sock() + raise N4Error.PunchFailure + + recv_punch_pkt, recv_peer = r[0].recvfrom(0xffff) + if recv_peer[0] == peer[0] and recv_punch_pkt == punch_pkt: + break + + logging.info(" => Punch from peer ") + + # Now UDP hole punching is successful. + # send ten times back to peer to avoid packet loss + for _ in range(10): + r[0].sendto(punch_pkt, recv_peer) + time.sleep(0.2) + + logging.info(" <= Punch ") + + _, src_port = r[0].getsockname() + self._close_all_sock() + + return recv_peer, src_port + + +def srv_main(): + ident = args.a + port = args.l + while True: + n4s = N4Server(ident, port) + n4s.serve() + + +def cli_main(): + ident = args.a + server_host = args.h + server_port = args.p + port = args.b + count = args.n + offset = args.o + while True: + try: + n4c = N4Client( + ident=ident, + server_host=server_host, + server_port=server_port, + src_port_start=port, + src_port_count=count, + peer_port_offset=offset + ) + logging.info("==================") + logging.info("Source port: %d-%d" % (port, port+count)) + peer, src_port = n4c.punch(wait=10) + peer_ip, peer_port = peer + logging.info("------") + logging.info("Local port: %d" % src_port) + logging.info("Peer address: %s:%d" % (peer_ip, peer_port)) + logging.info("------") + logging.info("[ WIN ]") + logging.info("------") + logging.info("> nc -u -p %d %s %d" % (src_port, peer_ip, peer_port)) + break + except N4Error.PunchFailure: + logging.info("[ LOSE ]") + port += count + continue + + +def main() -> None: + global args + + def ident_t(a): + b = str(a).encode("ascii", "ignore").ljust(6) + if len(b) != 6: + raise ValueError + return b + + argp = argparse.ArgumentParser(add_help=False) + group = argp.add_argument_group("options") + group.add_argument( + "-a", type=ident_t, metavar="", default=b"n4n4n4", + help="identifier (6 chars max)" + ) + group = argp.add_argument_group("server options") + group.add_argument( + "-s", action="store_true", help="run in server mode" + ) + group.add_argument( + "-l", type=int, metavar="", default=1721, + help="set server port to listen on" + ) + group = argp.add_argument_group("client options") + group.add_argument( + "-c", action="store_true", help="run in client mode" + ) + group.add_argument( + "-b", type=int, metavar="", default=30000, + help="source port start" + ) + group.add_argument( + "-n", type=int, metavar="", default=25, + help="source port count" + ) + group.add_argument( + "-o", type=int, metavar="", default=20, + help="peer port offset" + ) + group.add_argument( + "-h", type=str, help="hostname of N4 server (required)", default=None + ) + group.add_argument( + "-p", type=int, help="port of N4 server", default=1721 + ) + args = argp.parse_args() + if args.s: + srv_main() + elif args.c and args.h: + cli_main() + else: + argp.print_help() + + +if __name__ == "__main__": + main()