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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The loopback-specific guard in bindDevice is reverted — superseded by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
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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