x/sys/unix: missing socket constants

[AlonZivony]

What version of Go are you using (go version)?

$ go version 1.18.2

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/alonz/.cache/go-build"
GOENV="/home/alonz/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/alonz/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/alonz/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/alonz/go/src/libbpfgo/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1901468926=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I am using the x/sys/unix pacakge.
I want to support all possible socket level and optname values for the setsocketopt syscall, but some of the values have no constants (because they are from newer kernel versions).

The following values are missing:

• level:

  • SOL_MCTCP
  • SOL_MCTP
  • SOL_SMC

• optname:

  • SO_NETNS_COOKIE
  • SO_BUF_LOCK
  • SO_RESERVE_MEM
  • SO_TXREHASH

What did you expect to see?

I want to use the values like the following - unix.SOL_MCTCP.

[seankhliao]

From https://pkg.go.dev/golang.org/x/sys/unix the only ones I see missing are "SOL_MCTCP" and "SOL_SMC", but I also don't see "SOL_MCTCP" mentioned anywhere on the internet at all?

[AlonZivony]

You are right, it seems that the optname values are available in the newest version.
About the missing level values - you can see that they are supported by the newest kernel in the following source code page - https://elixir.bootlin.com/linux/latest/source/include/linux/socket.h#L330

[tklauser]

I assume you meant SOL_MPTCP, not SOL_MCTCP?

All but SOL_SMC should be in latest tip of the package:

% git grep -E "SOL_(MPTCP|MCTP|SMC)"
zerrors_linux.go:2583:  SOL_MCTP                                    = 0x11d
zerrors_linux.go:2584:  SOL_MPTCP                                   = 0x11c

It seems we generate these constants from glibc's sys/socket.h, and glibc 2.35 which we currently use to generate the constants doesn't seem to have SOL_SMC yet. If we want SOL_SMC now, without waiting for a glibc version providing it, we could probably add it similarly to how SOL_NETLINK is defined: https://cs.opensource.google/go/x/sys/+/87e55d71:unix/mkerrors.sh;l=294-296

[gopherbot]

Change https://go.dev/cl/417994 mentions this issue: unix: add socket constants

[ianwoolf]

Do the following source code pages support the missing optname? I send a cl according to the following code.

https://elixir.bootlin.com/linux/latest/source/include/uapi/asm-generic/socket.h#L125

[ianwoolf]

I assume you meant SOL_MPTCP, not SOL_MCTCP?

All but SOL_SMC should be in latest tip of the package:

% git grep -E "SOL_(MPTCP|MCTP|SMC)"
zerrors_linux.go:2583:  SOL_MCTP                                    = 0x11d
zerrors_linux.go:2584:  SOL_MPTCP                                   = 0x11c

It seems we generate these constants from glibc's sys/socket.h, and glibc 2.35 which we currently use to generate the constants doesn't seem to have SOL_SMC yet. If we want SOL_SMC now, without waiting for a glibc version providing it, we could probably add it similarly to how SOL_NETLINK is defined: https://cs.opensource.google/go/x/sys/+/87e55d71:unix/mkerrors.sh;l=294-296

the level add to glibc at the following commit

• https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=6488f4d00653b489e7969c0a489dc665c26514a8;hp=81e7fdd7ccff3745db0b0d8ffa1ec9fab6dcee67
• https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=fdc1ae67fef27eea1445bab4bdfe2f0fb3bc7aa1;hp=2c0915cbf570cb9c8a65f1d20a55c5a7238e5b63

glibc 2.35 not contain these commit. So glibc 2.35 which we currently use to generate the constants doesn't have SOL_SMC SOL_MPTCP and SOL_MCTP yet.

Do we need to wait for glibc to release?

@ianlancetaylor

[ianlancetaylor]

We don't have to wait for glibc. But we do need to ensure that anything we do is correct for all supported operating systems. I'm frankly pretty skeptical about the SOL_NETLINK code mentioned above.