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net: use correct address family when testing for MPTCP support

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Before this patch, on a system that only supports IPv6, we would
get EAFNOSUPPORT and decide that MPTCP might be available later.
The effect is that every socket tries to get MPTCP. If the system
does not support MPTCP, every socket call turns into two system calls.

Also avoid the uname if MPTCP is not supported.

For #56539

Change-Id: I628b44eda83b455f5493a9dd59076f1acea2f65b
Reviewed-on: https://go-review.googlesource.com/c/go/+/616335
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Ian Lance Taylor 2024-09-27 10:17:48 -07:00 committed by Gopher Robot
parent ba10a38ed0
commit aec9b916a2
1 changed files with 13 additions and 2 deletions
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15
src/net/mptcpsock_linux.go
View File

@ -16,7 +16,7 @@ import (
var (
mptcpOnce sync.Once
mptcpAvailable bool
hasSOLMPTCP bool
hasSOLMPTCP bool // only valid if mptcpAvailable is true
)
// These constants aren't in the syscall package, which is frozen
@ -34,10 +34,17 @@ func supportsMultipathTCP() bool {
// Check that MPTCP is supported by attempting to create an MPTCP socket and by
// looking at the returned error if any.
func initMPTCPavailable() {
s, err := sysSocket(syscall.AF_INET, syscall.SOCK_STREAM, _IPPROTO_MPTCP)
family := syscall.AF_INET
if !supportsIPv4() {
family = syscall.AF_INET6
}
s, err := sysSocket(family, syscall.SOCK_STREAM, _IPPROTO_MPTCP)
switch {
case errors.Is(err, syscall.EPROTONOSUPPORT): // Not supported: >= v5.6
return
case errors.Is(err, syscall.EINVAL): // Not supported: < v5.6
return
case err == nil: // Supported and no error
poll.CloseFunc(s)
fallthrough
@ -119,6 +126,10 @@ func isUsingMPTCPProto(fd *netFD) bool {
// Please look at the description of hasFallenBack (kernel >=5.16) and
// isUsingMPTCPProto methods for more details about what is being checked here.
func isUsingMultipathTCP(fd *netFD) bool {
if !supportsMultipathTCP() {
return false
}
if hasSOLMPTCP {
return !hasFallenBack(fd)
}