Comment 1:

Tracing the problem:
- selfConnect is getting a *netFD with a nil raddr field.
- that fd is coming from internetSocket, which must be returning no error.
From the other end:
- DialTCP checks for raddr==nil, so raddr.toAddr() must be a non-nil sockaddr.
- internetSocket must call raddr.sockaddr (*TCPAddr.sockaddr), which only returns a
non-nil syscall.Sockaddr with nil error (and so ra is non-nil).
- This means that the problem must be socket returning an fd with a nil raddr even if
its ra argument is non-nil.
- That, in turn, means the toAddr func passed to socket (and internetSocket) must be
doing that.
- This fingers sockaddrToTCP, which will return nil if the syscall.Sockaddr is not one
of {*syscall.SockaddrInet4,*syscall.SockaddrInet6}.
- However, ipToSockaddr never returns a different type than those two, except with an
error.
Here the trail runs cold. I can't see what is going wrong without a way to reproduce
this and scattering some logging throughout. All I can think of is that it slipped in
with 002f08814913 (Russ' "net: avoid TCP self-connect"), so assigning it to him for
further diagnosis.

Labels changed: added priority-later, removed priority-triage.

Owner changed to @rsc.

Comment 2:

Labels changed: added priority-go1, removed priority-later.

Comment 3:

It took a long time, but running the test repeatedly eventually reproduced this.
#!/bin/bash
set -xe
rm -f out err net.test
go test -c net
while true; do
for procs in 1 2 8 10 50 100; do
GOMAXPROCS=$procs time ./net.test -test.v >out 2>err || exit 1
echo $?
done
done

Comment 4:

I notice that the Linux ARM builder is reproducibly giving the same failure, every time
it seems. for instance,
http://build.golang.org/log/5fd6fdde31381ed018fbaa55af7132cc72fbda8b
goroutine 236 [running]:
net.selfConnect(0x107ab9a0, 0x3, 0x0)
    /mnt/work2/tmp/gobuilder/linux-arm-minux-2c15f43065c1/go/src/pkg/net/tcpsock_posix.go:263 +0x84
net.DialTCP(0x15ad68, 0x3, 0x0, 0x1079c6d0, 0x10732801, ...)
    /mnt/work2/tmp/gobuilder/linux-arm-minux-2c15f43065c1/go/src/pkg/net/tcpsock_posix.go:250 +0x218
net.dialAddr(0x15ad68, 0x3, 0x107805f0, 0xf, 0x10732860, ...)
    /mnt/work2/tmp/gobuilder/linux-arm-minux-2c15f43065c1/go/src/pkg/net/dial.go:102 +0x1fc
net._func_001(0x107838a8, 0x107838b0, 0x107838b8, 0x107838c0, 0x0, ...)
    /mnt/work2/tmp/gobuilder/linux-arm-minux-2c15f43065c1/go/src/pkg/net/dial.go:140 +0x1ac
created by net.DialTimeout
    /mnt/work2/tmp/gobuilder/linux-arm-minux-2c15f43065c1/go/src/pkg/net/dial.go:142 +0x194

Comment 5:

Labels changed: added go1-must.

Comment 6:

This issue was closed by revision 152d806.

Status changed to Fixed.