net: use port 53 when checking for UDP routes

Using port 9 is weird and at least once triggered a suspicious
activity alert.

Fixes #67264

Change-Id: If4179f054829c175b9f3a51c3bc2a3ca4afa74b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/584416
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>

diff --git a/src/net/addrselect.go b/src/net/addrselect.go
index 4f07032c4a01dbac7e13ff4e4a42ad164215eb20..caff09b3772ff76c6a5b286671202cecfa37dcd3 100644 (file)
--- a/src/net/addrselect.go
+++ b/src/net/addrselect.go
@@ -42,7 +42,7 @@ func sortByRFC6724withSrcs(addrs []IPAddr, srcs []netip.Addr) {
 // number is irrelevant.
 func srcAddrs(addrs []IPAddr) []netip.Addr {
        srcs := make([]netip.Addr, len(addrs))
-       dst := UDPAddr{Port: 9}
+       dst := UDPAddr{Port: 53}
        for i := range addrs {
                dst.IP = addrs[i].IP
                dst.Zone = addrs[i].Zone