Categorygithub.com/jordansissel/experimentsgounixgram-broken
package
0.0.0-20241220054012-2e42123f823d
Repository: https://github.com/jordansissel/experiments.git
Documentation: pkg.go.dev
Overview
Dependencies
3
Dependents
0

# README

go + unix datagram == :(

Example

  • Note: to send a message to this socket, on linux, use logger -du /tmp/example.sock hello world

    % rm /tmp/example.sock; strace -e trace=socket,connect,recvfrom,open ./example socket(PF_FILE, SOCK_DGRAM, 0) = 3 recvfrom(3, 0xf84006e000, 4096, 0, 0xf840000150, 0xf8400490a0) = -1 EAGAIN (Resource temporarily unavailable) recvfrom(3, "<5>Jul 27 23:21:39 jls: hello\0", 4096, 0, {sa_family=AF_UNSPEC, sa_data="\0\0\0\0\0\0\0\0\0\0\0\0\0\0"}, [0]) = 30 conn.ReadFrom error: read unixgram /tmp/example.sock: address family not supported by protocol +++ exited with 0 +++

Thoughts

The error from conn.ReadFrom fails, yet strace reveals that the recvfrom(2) call is successful.

There's a bug somewhere in Go, here. Some likely problems:

  • net.ListenUnixgram returns, quite confusingly, a UDPConn, shouldn't this return a UnixConn?
  • I suspect the recvfrom(2) syscall returns an address type that UDPConn cannot understand, and thus the error given by Go 'address family not supported by protocol'.

Fixing

A test, before the fix:

% GOPATH=$PWD/../ go test pkg/net/
--- FAIL: TestListenUnixgramReadFromUnix (0.00 seconds)
        unixgram_test.go:49: UnixConn.ReadFrom failed: read unixgram /tmp/example.sock: address family not supported by protocol
        FAIL
        FAIL    pkg/net 14.009s

After: