tr-bridge: manually filter non-LLC frames in software

tr-bridge.c

@@ -214,6 +214,11 @@ static int eth2tr(struct bridge_state *bst)
 		return 0;
 	}
 
+	if (ethh->h_proto != htons(ETH_P_802_2)) {
+		fprintf(stderr, "TR<-ETH: Not bridging unexpected frame for proto 0x%04x\n", ntohs(ethh->h_proto));
+		return 0;
+	}
+
 	trh.ac = AC;
 	trh.fc = LLC_FRAME;
 	memcpy(&trh.daddr, ethh->h_dest, sizeof(trh.daddr));
@@ -259,6 +264,11 @@ static int tr2eth(struct bridge_state *bst)
 		return 0;
 	}
 
+	if (trh->fc != LLC_FRAME) {
+		fprintf(stderr, "TR->ETH: Not bridging unexpected non-LLC frame for FC 0x%02x\n", trh->fc);
+		return 0;
+	}
+
 	memcpy(&ethh.h_dest, trh->daddr, sizeof(ethh.h_dest));
 	osmo_revbytebits_buf(ethh.h_dest, TR_ALEN);
 	memcpy(&ethh.h_source, trh->saddr, sizeof(ethh.h_source));