syscall: fix ParseRoutingSockaddr with unexpected submessages

No easy way to test (would have to actually trigger some routing
events from kernel) but the code is clearly wrong as written.
If the header says there is a submessage, we need to at least
skip over its bytes, not just continue to the next iteration.

Fixes #8203.

LGTM=r
R=r
CC=golang-codereviews, mikioh.mikioh, p
https://golang.org/cl/164140044

diff --git a/src/syscall/route_bsd.go b/src/syscall/route_bsd.go
index 48af587450ba1eca15cbd56abc775c41f3c36670..1dabe42531b77da5e407d7f1009de20129e697a8 100644 (file)
--- a/src/syscall/route_bsd.go
+++ b/src/syscall/route_bsd.go
@@ -153,7 +153,7 @@ func (m *InterfaceAddrMessage) sockaddr() (sas []Sockaddr) {
        // RTAX_NETMASK socket address on the FreeBSD kernel.
        preferredFamily := uint8(AF_UNSPEC)
        for i := uint(0); i < RTAX_MAX; i++ {
-               if m.Header.Addrs&rtaIfaMask&(1<<i) == 0 {
+               if m.Header.Addrs&(1<<i) == 0 {
                        continue
                }
                rsa := (*RawSockaddr)(unsafe.Pointer(&b[0]))