if_wg: better loop detection

While it was nice to have per peer loop detection, it was not meant to
be. The loop tag has a tag type == 0, which conflicts with other tags.
Therefore we want to at least be a little bit more sure that the tag
cookie is unique to the loop tag. I guess the peer address was also
quite hacky so on the other side, I'm glad to be rid of that.

Now we have a loop of 8 (to any peer) which should be good enough for an
edge case operation.

Signed-off-by: Matt Dunwoodie <ncon@noconroy.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/if_wg.c b/src/if_wg.c
index 46a9910..9984a1e 100644
--- a/src/if_wg.c
+++ b/src/if_wg.c
@@ -272,6 +272,9 @@ struct wg_softc {
 
 #define	WGF_DYING	0x0001
 
+#define MAX_LOOPS	8
+#define MTAG_WGLOOP	0x77676c70 /* wglp */
+
 /* TODO the following defines are freebsd specific, we should see what is
  * necessary and cleanup from there (i suspect a lot can be junked). */
 
@@ -2006,9 +2009,7 @@ wg_transmit(struct ifnet *ifp, struct mbuf *m)
 		goto err;
 	}
 
-	/* Detect packet loops, TODO make better unique identifier than p_id
-	 * (because it is truncated from uint64_t to uint32_t). */
-	if (__predict_false(if_tunnel_check_nesting(ifp, m, peer->p_id, 1))) {
+	if (__predict_false(if_tunnel_check_nesting(ifp, m, MTAG_WGLOOP, MAX_LOOPS))) {
 		DPRINTF(sc, "Packet looped");
 		rc = ELOOP;
 		goto err;