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unix: drop dummy byte for oob in unixgram SendmsgN

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This commit relaxes SendmsgN behavior of introducing a dummy 1-byte
payload when sending ancillary-only messages.
The fake payload is not needed for SOCK_DGRAM type sockets, and actually
breaks interoperability with other fd-passing software (journald is one
known example). This introduces an additional check to avoid injecting
dummy payload in such case.

Backport of https://go.googlesource.com/go/+/93da0b6e66f24c4c307e0df37ceb102a33306174
Full reference at https:/golang.org/issue/6476#issue-51285243

Change-Id: I7cf00a1c7cde75fe62e00b98ccba6ac8469b0493
Reviewed-on: https://go-review.googlesource.com/60190
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Luca Bruno
2017-08-30 13:42:02 +00:00
committed by Ian Lance Taylor
parent ab9e364efd
commit bb24a47a89
2 changed files with 112 additions and 87 deletions
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unix/syscall_linux.go
+12 -2
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@@ -931,8 +931,13 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
}
var dummy byte
if len(oob) > 0 {
var sockType int
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
if err != nil {
return
}
// receive at least one normal byte
if len(p) == 0 {
if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy
iov.SetLen(1)
}
@@ -978,8 +983,13 @@ func SendmsgN(fd int, p, oob []byte, to Sockaddr, flags int) (n int, err error)
}
var dummy byte
if len(oob) > 0 {
var sockType int
sockType, err = GetsockoptInt(fd, SOL_SOCKET, SO_TYPE)
if err != nil {
return 0, err
}
// send at least one normal byte
if len(p) == 0 {
if sockType != SOCK_DGRAM && len(p) == 0 {
iov.Base = &dummy
iov.SetLen(1)
}