Now you are be able to capture traffic inside k8s like this:
```
gor --input-raw k8s://namespace/deployment/app:80 --output-http http://replay.com
```
Supported format for filtering required pods:
```
k8s://[namespace/]pod/[pod_name] - k8s://default/pod/nginx-7848d4b86f-5nxz8
k8s://[namespace/]deployment/[deployment_name] - k8s://default/deployment/nginx
k8s://[namespace/]daemonset/[daemonset_name] - k8s://default/daemonset/nginx
k8s://[namespace/]labelSelector/[selector] - k8s://default/labelSelector/app=nginx
k8s://[namespace/]fieldSelector/[selector] - k8s://default/fieldSelector/metadata.name=nginx-7848d4b86f-5nxz8
```
`namespace` is optional, omit to use all namespaces: `k8s://labelSelector/app=replay`
GoReplay designed to be running running as a daemonset (e.g. on each physical k8s node).
See the full guide in here: https://github.com/buger/goreplay/blob/ca8205a5c5d2a1facb00214c78e4120aae6d772d/k8s/README.md
The cause was not ZeroCopy but wrong SetTimeout (block cause a lot of overhead).
Packet processing previously used channels, but now, with ring buffer, using select was causing issue. Adding `default` clause fixed the issue.
Issues is that Go built-in net.Interfaces function in newer Windows versions return wrong interface names, which libpcap can't consume.
Now we use pcap.FindDevices instead of net.Interfaces.
See this Article for deep understanding of the issue https://haydz.github.io/2020/07/06/Go-Windows-NIC.html
Additionally, found a bug causing big memory allocations, for large requests, when we perform check if messages finished or not.
Because of this bug chunked body encoding check was not working properly.
Was not caught in tests, because test was working on packet array level, and this issue happens when dealing with TCP message object.
Additionally, added a small fix for windows Makefile task, it now generates proper file name.
### Reducing CPU context switching and number of goroutines.
Packet capture and packet processing now use only two goroutines which helps to minimize CPU context switches. Spawning too many goroutines is harmful here.
### Optimized packet capture - allocated memory only when required, and only for data which is used
Using ZeroCopy methods from libpcap library to avoid unnecessary allocations. Now memory gets allocated ONLY for the valid packets, and only for the packets which have the data. E.g. no SYN/FIN packets are used now. Additionally we now use `sync.Pool` for re-using packet objects, which helps to re-use already allocated memory.
### Simplification and optimization of request/response detection
There is no SYN/FIN packets anymore etc. Now only packet payload is used to detect start and end of the packet. More over payload detection now does not require generating a total “message” buffer, and works with individual packet payloads.
Message payloads now concatenated from packets only in the end when message is dispatched. Also, before checking if message is complete, added additional check if all received packets in the valid order, e.g. if their SEQ is valid, and no packets are missing.
Reworked chunked encoding validation, and now it does not need expensive operation of re-calculating all the chunks. Now it “trust” that client gives valid chunk body, check if packets are in the right order (e.g. SEQ match), and checks if message ends with the right suffix. All is done with 0 allocations.
Parsing all Headers using `proto.GetHeaders` was proved to be very slow. Now we only parse the headers we need(and do it only once).
Packets gets matched together using ACK, which on high RPS removed chances of duplicating IDs. Additionally, even if packets are received out of order, now it will properly sort them, before dispatching the message.
### Changes in ID generation algorithm
Message ID generation and relations between request and response IDs is fully rewritten. Responses now do not have to lookup for request data in order to get the same ID. ID no rely on the fact that SEQ of the first packet of the response should be the same as ACK of the request. If previously Message ID contained random values, like current timestamp, now it has a consistent algorithm which is based on TCP stream id (SrcPort + DstPort + SrcIP/DstIP) and current ACK/SEQ number (to distinguish multiple messages within the same stream).
### BPF filter optimizations
When tracking response it now uses a more accurate BPF rule to filter only needed traffic.
### Misc
The packet code is now fully moved to tcp/Packet, so packet processing done only once in one place.
TCP output now has a 5 second timeout, and has a proper Close method.
Fully switching to go modules and removing vendoring.
## Description
Hi 👋 I ran the [DeepSource](https://deepsource.io/) static analyzer on the forked copy of this repo and found some [interesting code quality issues](https://deepsource.io/gh/ankitdobhal/goreplay/issues/). This PR fixes a few of them.
## Summary of Fixes
- Added .deepsource.toml to fix bug risks
- Empty string test can be improved
- Nested if can be replaced with else-if
## Type of change
- [✔] Antipattern
- [ ] New feature (non-breaking change which adds functionality)
## Checklist:
- [✔] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have made corresponding changes to the documentation
This is to make socket implementations independent of the host OS.
this is done by creating an interface that define all required behaviors of the socket.
