icmp: Don't attempt to handle "wrong direction" ping socket traffic

Linux ICMP "ping" sockets are very specific in what they do.  They let
userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive
matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY).  They don't let you
intercept or handle incoming ping requests.

In the case of passt/pasta that means we can process echo requests from tap
and forward them to a ping socket, then take the replies from the ping
socket and forward them to tap.  We can't do the reverse: take echo
requests from the host and somehow forward them to the guest. There's
really no way for something outside to initiate a ping to a passt/pasta
connected guest and if there was we'd need an entirely different mechanism
to handle it.

However, we have some logic to deal with packets going in that reverse
direction.  Remove it, since it can't ever be used that way.  While we're
there use defines for the ICMPv6 types, instead of open coded type values.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 6 insertions, 10 deletions

diff --git a/icmp.c b/icmp.c
index ed1a3d9..697a336 100644
--- a/icmp.c
+++ b/icmp.c
@@ -93,8 +93,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V4][id].seq = seq;
 	}
 
-	debug("ICMP: echo %s to tap, ID: %i, seq: %i",
-	      (ih->type == ICMP_ECHO) ? "request" : "reply", id, seq);
+	debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n);
 }
@@ -138,8 +137,7 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref)
 		icmp_id_map[V6][id].seq = seq;
 	}
 
-	debug("ICMPv6: echo %s to tap, ID: %i, seq: %i",
-	      (ih->icmp6_type == 128) ? "request" : "reply", id, seq);
+	debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq);
 
 	tap_icmp6_send(c, &sr.sin6_addr,
 		       tap_ip6_daddr(c, &sr.sin6_addr), buf, n);
@@ -178,7 +176,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY)
+		if (ih->type != ICMP_ECHO)
 			return 1;
 
 		iref.id = id = ntohs(ih->un.echo.id);
@@ -205,8 +203,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 			debug("ICMP: failed to relay request to socket");
 		} else {
-			debug("ICMP: echo %s to socket, ID: %i, seq: %i",
-			      (ih->type == ICMP_ECHO) ? "request" : "reply",
+			debug("ICMP: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->un.echo.sequence));
 		}
 	} else if (af == AF_INET6) {
@@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 		if (!ih)
 			return 1;
 
-		if (ih->icmp6_type != 128 && ih->icmp6_type != 129)
+		if (ih->icmp6_type != ICMPV6_ECHO_REQUEST)
 			return 1;
 
 		iref.id = id = ntohs(ih->icmp6_identifier);
@@ -249,8 +246,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
 			   (struct sockaddr *)&sa, sizeof(sa)) < 1) {
 			debug("ICMPv6: failed to relay request to socket");
 		} else {
-			debug("ICMPv6: echo %s to socket, ID: %i, seq: %i",
-			      (ih->icmp6_type == 128) ? "request" : "reply",
+			debug("ICMPv6: echo request to socket, ID: %i, seq: %i",
 			      id, ntohs(ih->icmp6_sequence));
 		}
 	}