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net: in (*netFD).dial, use the passed in local address if getsockname fails

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'man getsockname' lists a number of possible failure modes, including
ENOBUFS (for resource exhaustion) and EBADF (which we could possibly
see in the event of a bug or race condition elsewhere in the program).

If getsockname fails for an explicit user-provided local address, the
user is probably not expecting LocalAddr on the returned net.Conn to
return nil. This may or may not fix #34611, but should at least help
us diagnose it more clearly.

While we're add it, also add more nil-checking logic in the test based
on the stack traces posted to
https://golang.org/issue/34611#issuecomment-975923748.

For #34611

Change-Id: Iba870b96787811e4b9959b74ef648afce9316602
Reviewed-on: https://go-review.googlesource.com/c/go/+/366536
Trust: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Bryan C. Mills 2021-11-23 10:27:30 -05:00 committed by Bryan Mills
parent 0eb39ca1f0
commit e07b02ff87
2 changed files with 20 additions and 6 deletions
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10
src/net/server_test.go
View File

@ -200,9 +200,17 @@ func TestUnixAndUnixpacketServer(t *testing.T) {
if c == nil {
panic("Dial returned a nil Conn")
}
if rc := reflect.ValueOf(c); rc.Kind() == reflect.Pointer && rc.IsNil() {
rc := reflect.ValueOf(c)
if rc.IsNil() {
panic(fmt.Sprintf("Dial returned a nil %T", c))
}
fd := rc.Elem().FieldByName("fd")
if fd.IsNil() {
panic(fmt.Sprintf("Dial returned a %T with a nil fd", c))
}
if addr := fd.Elem().FieldByName("laddr"); addr.IsNil() {
panic(fmt.Sprintf("Dial returned a %T whose fd has a nil laddr", c))
}
addr := c.LocalAddr()
if addr == nil {
panic(fmt.Sprintf("(%T).LocalAddr returned a nil Addr", c))

16
src/net/sock_posix.go
View File

@ -156,18 +156,24 @@ func (fd *netFD) dial(ctx context.Context, laddr, raddr sockaddr, ctrlFn func(st
}
}
// Record the local and remote addresses from the actual socket.
// Get the local address by calling Getsockname.
// For the local address, use
// 1) the one returned by Getsockname, if that succeeds; or
// 2) the one passed to us as the laddr parameter; or
// 3) nil.
// For the remote address, use
// 1) the one returned by the connect method, if any; or
// 2) the one from Getpeername, if it succeeds; or
// 3) the one passed to us as the raddr parameter.
lsa, _ = syscall.Getsockname(fd.pfd.Sysfd)
var laddrName Addr = laddr
if lsa, err := syscall.Getsockname(fd.pfd.Sysfd); err == nil {
laddrName = fd.addrFunc()(lsa)
}
if crsa != nil {
fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(crsa))
fd.setAddr(laddrName, fd.addrFunc()(crsa))
} else if rsa, _ = syscall.Getpeername(fd.pfd.Sysfd); rsa != nil {
fd.setAddr(fd.addrFunc()(lsa), fd.addrFunc()(rsa))
fd.setAddr(laddrName, fd.addrFunc()(rsa))
} else {
fd.setAddr(fd.addrFunc()(lsa), raddr)
fd.setAddr(laddrName, raddr)
}
return nil
}