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fix(dialer): skip SO_BINDTODEVICE when interface is specified as IP address

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When the user specifies an IP address as the interface (e.g.
interface=10.1.1.1), GOST resolved it to its hosting interface and
called SO_BINDTODEVICE on it — breaking outbound connectivity for
IP aliases on loopback or dummy interfaces (go-gost/gost#785).

The initial fix (caa82f2) only skipped SO_BINDTODEVICE for loopback
interfaces, missing non-loopback dummy interfaces like ip-aliases.

This change adds an isIP return value to ParseInterfaceAddr so callers
can distinguish 'user specified an IP' (intent: source IP binding for
policy routing — skip SO_BINDTODEVICE) from 'user specified an
interface name' (intent: force traffic through that NIC — keep
SO_BINDTODEVICE). The dialOnce method now only calls bindDevice when
bindToDevice is true AND the input was an interface name (!isIP).

The loopback-specific guard in bindDevice is reverted — superseded by
the broader isIP-based fix that covers all interface types.
This commit is contained in:
ginuerzh
2026-06-23 21:43:54 +08:00
parent a32ffd5608
commit c06ba17916
4 changed files with 31 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files
internal/net/dialer/dialer.go
+5 -4
View File
@@ -76,13 +76,14 @@ func (d *Dialer) Dial(ctx context.Context, network, addr string) (conn net.Conn,
ifce = strings.TrimSuffix(ifce, "!")
var ifceName string
var ifAddrs []net.Addr
ifceName, ifAddrs, err = xnet.ParseInterfaceAddr(ifce, network)
var isIP bool
ifceName, ifAddrs, isIP, err = xnet.ParseInterfaceAddr(ifce, network)
if err != nil && strict {
return
}
for _, ifAddr := range ifAddrs {
conn, err = d.dialOnce(ctx, network, addr, ifceName, ifAddr, log)
conn, err = d.dialOnce(ctx, network, addr, ifceName, ifAddr, !isIP, log)
if err == nil {
return
}
@@ -100,7 +101,7 @@ func (d *Dialer) Dial(ctx context.Context, network, addr string) (conn net.Conn,
return
}
func (d *Dialer) dialOnce(ctx context.Context, network, addr, ifceName string, ifAddr net.Addr, log logger.Logger) (net.Conn, error) {
func (d *Dialer) dialOnce(ctx context.Context, network, addr, ifceName string, ifAddr net.Addr, bindToDevice bool, log logger.Logger) (net.Conn, error) {
if ifceName != "" {
log.Debugf("dial %s/%s via interface %s@%s", addr, network, ifceName, ifAddr)
}
@@ -148,7 +149,7 @@ func (d *Dialer) dialOnce(ctx context.Context, network, addr, ifceName string, i
LocalAddr: ifAddr,
Control: func(network, address string, c syscall.RawConn) error {
return c.Control(func(fd uintptr) {
if ifceName != "" {
if ifceName != "" && bindToDevice {
if err := bindDevice(network, address, fd, ifceName); err != nil {
log.Warnf("%s/%s bind device: %v", address, network, err)
}
internal/net/dialer/dialer_linux.go
-8
View File
@@ -11,14 +11,6 @@ func bindDevice(network, address string, fd uintptr, ifceName string) error {
return nil
}
// Skip SO_BINDTODEVICE for loopback interface — it prevents
// outbound traffic from reaching non-local destinations.
// Source IP binding via LocalAddr is sufficient for policy routing
// when using IP aliases on loopback (e.g. ip addr add 10.1.1.1/32 dev lo).
if ifce, err := net.InterfaceByName(ifceName); err == nil && ifce.Flags&net.FlagLoopback != 0 {
return nil
}
host, _, _ := net.SplitHostPort(address)
if ip := net.ParseIP(host); ip != nil && !ip.IsGlobalUnicast() {
return nil