net: SIGSEGV in selfConnect

[bcmills]

--- FAIL: TestListenerClose (0.00s)
    --- FAIL: TestListenerClose/tcp (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x55c936]

goroutine 4380 [running]:
panic({0x62ab00, 0x7d2000})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/panic.go:941 +0x397 fp=0xc000379630 sp=0xc000379570 pc=0x4350b7
testing.tRunner.func1.2({0x62ab00, 0x7d2000})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/testing/testing.go:1360 +0x24e fp=0xc0003796e0 sp=0xc000379630 pc=0x4d55ce
testing.tRunner.func1()
	/tmp/workdir-host-dragonfly-amd64-master/go/src/testing/testing.go:1363 +0x39f fp=0xc000379848 sp=0xc0003796e0 pc=0x4d505f
runtime.deferCallSave(0xc000379918, 0xc000329f90?)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/panic.go:750 +0x82 fp=0xc000379858 sp=0xc000379848 pc=0x434cc2
runtime.runOpenDeferFrame(0xc00035d310?, 0xc00035d360)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/panic.go:723 +0x1a5 fp=0xc0003798a0 sp=0xc000379858 pc=0x434ae5
panic({0x62ab00, 0x7d2000})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/panic.go:838 +0x207 fp=0xc000379960 sp=0xc0003798a0 pc=0x434f27
runtime.panicmem(...)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/panic.go:220
runtime.sigpanic()
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/signal_unix.go:797 +0x336 fp=0xc0003799b0 sp=0xc000379960 pc=0x44b4f6
net.selfConnect(0x0?, {0x0?, 0x0?})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/tcpsock_posix.go:123 +0x56 fp=0xc0003799f0 sp=0xc0003799b0 pc=0x55c936
net.(*sysDialer).doDialTCP(0xc0001c4580, {0x6b5ed8, 0xc000016168}, 0x0, 0x9?)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/tcpsock_posix.go:91 +0x19c fp=0xc000379a98 sp=0xc0003799f0 pc=0x55c6fc
net.(*sysDialer).dialTCP(0x1?, {0x6b5ed8?, 0xc000016168?}, 0xc000132480?, 0x6226e0?)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/tcpsock_posix.go:61 +0x59 fp=0xc000379ad8 sp=0xc000379a98 pc=0x55c4f9
net.(*sysDialer).dialSingle(0xc0001c4580, {0x6b5ed8, 0xc000016168}, {0x6b5690?, 0xc0001c2780})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/dial.go:583 +0x28b fp=0xc000379ba8 sp=0xc000379ad8 pc=0x532bcb
net.(*sysDialer).dialSerial(0xc0001c4580, {0x6b5ed8, 0xc000016168}, {0xc00016c350?, 0x1, 0x6618c1?})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/dial.go:551 +0x312 fp=0xc000379cb0 sp=0xc000379ba8 pc=0x532512
net.(*Dialer).DialContext(0xc000379e38, {0x6b5ed8, 0xc000016168}, {0x661730, 0x3}, {0xc00009cb60, 0xf})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/dial.go:428 +0x736 fp=0xc000379e00 sp=0xc000379cb0 pc=0x531396
net.(*Dialer).Dial(...)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/dial.go:351
net.Dial({0x661730?, 0x3?}, {0xc00009cb60?, 0x4d4b00?})
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/dial.go:319 +0x7a fp=0xc000379ea8 sp=0xc000379e00 pc=0x530b7a
net.TestListenerClose.func1(0xc000414000)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/net/net_test.go:275 +0x395 fp=0xc000379f70 sp=0xc000379ea8 pc=0x5b9b55
testing.tRunner(0xc000414000, 0xc0000960c0)
	/tmp/workdir-host-dragonfly-amd64-master/go/src/testing/testing.go:1410 +0x102 fp=0xc000379fc0 sp=0xc000379f70 pc=0x4d4c02
testing.(*T).Run.func1()
	/tmp/workdir-host-dragonfly-amd64-master/go/src/testing/testing.go:1457 +0x2a fp=0xc000379fe0 sp=0xc000379fc0 pc=0x4d5aaa
runtime.goexit()
	/tmp/workdir-host-dragonfly-amd64-master/go/src/runtime/asm_amd64.s:1571 +0x1 fp=0xc000379fe8 sp=0xc000379fe0 pc=0x465ca1
created by testing.(*T).Run
	/tmp/workdir-host-dragonfly-amd64-master/go/src/testing/testing.go:1457 +0x35f

The faulting line is here:
https://cs.opensource.google/go/go/+/master:src/net/tcpsock_posix.go;l=123;drc=f229e7031a6efb2f23241b5da000c3b3203081d6

Just a few lines above that, there is a // TODO: try to understand what's really going on. dating to CL 5687060 (2012-02-21). 😅
See previously #14124, #38700.

[bcmills]

The only failure like this in the logs is after CL 366536, so it seems somewhat likely that that change resulted in a new failure mode (perhaps a different form of #38700). Given that we're in the freeze, I'll revert that change and try a different approach.

greplogs --dashboard -md -l -e 'FAIL: TestListenerClose .*\n(?:\s+.*\n)*panic: runtime error: invalid memory address'

2021-12-07T18:58:57-4300f10/dragonfly-amd64

[gopherbot]

Change https://golang.org/cl/369982 mentions this issue: Revert "net: in (*netFD).dial, use the passed in local address if getsockname fails"

[bcmills]

Yep, definitely looking like a regression. Submitting the revert.

greplogs --dashboard -md -l -e '^goroutine \d+ \[running\]:\npanic.*\n\t.+\n(?:.+\n\t.+\n)*net\.selfConnect' --since=2021-01-01

2021-12-08T01:23:09-016e6eb/aix-ppc64
2021-12-07T18:58:57-4300f10/dragonfly-amd64