x/sys/unix: allow setting tcp repair options

[dandare100]

go version go1.16.5 linux/amd64

GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"

I would like to add a function (in syscall_unix.go) to set the socket repair options.
There are a few "typed" functions that exist already (unix.SetsockoptInt,SetsockoptInet4Addr,SetsockoptLinger) and I see this new function sitting alongside them.

The reason I would like to add it is because I cannot currently see a way to pass in the repair options in the way they need to be passed in.

An example of doing this call in C is

setsockopt(sk, SOL_TCP, TCP_REPAIR_OPTIONS,
opts, 4 * sizeof(struct tcp_repair_opt)

where opts is

struct tcp_repair_opt opts[4]

and tcp_repair_opts from tcp.h is

/* For socket repair options. */
struct tcp_repair_opt
{
u_int32_t opt_code;
u_int32_t opt_val;
};

There is no way (that I can see, please help if I am incorrect) to do this syscall in that manner, given the protection the go api has with the typed/named functions.

The work would be :

1. Add the tcp_repair_opt struct as TcpRepairOpt struct alongside the other structs in x/sys/unix/linux/types.go that are auto generated to x/sys/unix/ztypes_linux_amd64.go at build time. This tcp_repair_opt linux struct is currently found in the netinet/tcp.h linux header file

2. Add a function SetsockoptRepairOpt(fd, level, opt int, o []TcpRepairOpt) (err error) {

Would this be worth adding ?

[ianlancetaylor]

We don't usually use the proposal process for x/sys changes, which mostly just involve adding ways to access system-specific functionality.

This idea seems fine at first glance. Thanks.

[gopherbot]

Change https://golang.org/cl/332709 mentions this issue: unix: add SetsockoptTcpRepairOpt on Linux