tc: m_mirred: Add support for ingress redirect/mirror

So far, only the 'egress' direction was implemented.

Allow specifying 'ingress' as the direction packet appears on the target
interface.

For example, this takes incoming 802.1q frames on veth0 and redirects
them for input on dummy0:

 # tc filter add dev veth0 parent ffff: pref 1 protocol 802.1q basic \
     action mirred ingress redirect dev dummy0

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>

man/man8/tc-mirred.8

@@ -30,9 +30,7 @@ receives. Mirroring is what is sometimes referred to as Switch Port Analyzer
 .TQ
 .B egress
 Specify the direction in which the packet shall appear on the destination
-interface. Currently only
+interface.
-.B egress
-is implemented.
 .TP
 .B mirror
 .TQ

tc/m_mirred.c

@@ -62,13 +62,13 @@ static const char *mirred_n2a(int action)
 }
 
 static int
-parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
+parse_direction(struct action_util *a, int *argc_p, char ***argv_p,
-	     int tca_id, struct nlmsghdr *n)
+		int tca_id, struct nlmsghdr *n)
 {
 
 	int argc = *argc_p;
 	char **argv = *argv_p;
-	int ok = 0, iok = 0, mirror = 0, redir = 0;
+	int ok = 0, iok = 0, mirror = 0, redir = 0, ingress = 0, egress = 0;
 	struct tc_mirred p = {};
 	struct rtattr *tail;
 	char d[16] = {};
@@ -77,7 +77,21 @@ parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
 
 		if (matches(*argv, "action") == 0) {
 			break;
-		} else if (matches(*argv, "egress") == 0) {
+		} else if (!egress && matches(*argv, "egress") == 0) {
+			egress = 1;
+			if (ingress) {
+				fprintf(stderr, "Can't have both egress and ingress\n");
+				return -1;
+			}
+			NEXT_ARG();
+			ok++;
+			continue;
+		} else if (!ingress && matches(*argv, "ingress") == 0) {
+			ingress = 1;
+			if (egress) {
+				fprintf(stderr, "Can't have both ingress and egress\n");
+				return -1;
+			}
 			NEXT_ARG();
 			ok++;
 			continue;
@@ -96,7 +110,7 @@ parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
 					break;
 				}
 			} else if (!ok) {
-				fprintf(stderr, "was expecting egress (%s)\n", *argv);
+				fprintf(stderr, "was expecting egress or ingress (%s)\n", *argv);
 				break;
 
 			} else if (!mirror && matches(*argv, "mirror") == 0) {
@@ -105,7 +119,8 @@ parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
 					fprintf(stderr, "Can't have both mirror and redir\n");
 					return -1;
 				}
-				p.eaction = TCA_EGRESS_MIRROR;
+				p.eaction = egress ? TCA_EGRESS_MIRROR :
+					    TCA_INGRESS_MIRROR;
 				p.action = TC_ACT_PIPE;
 				ok++;
 			} else if (!redir && matches(*argv, "redirect") == 0) {
@@ -114,7 +129,8 @@ parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
 					fprintf(stderr, "Can't have both mirror and redir\n");
 					return -1;
 				}
-				p.eaction = TCA_EGRESS_REDIR;
+				p.eaction = egress ? TCA_EGRESS_REDIR :
+					    TCA_INGRESS_REDIR;
 				p.action = TC_ACT_STOLEN;
 				ok++;
 			} else if ((redir || mirror) && matches(*argv, "dev") == 0) {
@@ -154,7 +170,8 @@ parse_egress(struct action_util *a, int *argc_p, char ***argv_p,
 	}
 
 
-	if (argc && p.eaction == TCA_EGRESS_MIRROR
+	if (argc &&
+	    (p.eaction == TCA_EGRESS_MIRROR || p.eaction == TCA_INGRESS_MIRROR)
 	    && !action_a2n(*argv, &p.action, false))
 		NEXT_ARG();
 
@@ -207,8 +224,9 @@ parse_mirred(struct action_util *a, int *argc_p, char ***argv_p,
 	}
 
 
-	if (matches(*argv, "egress") == 0 || matches(*argv, "index") == 0) {
+	if (matches(*argv, "egress") == 0 || matches(*argv, "ingress") == 0 ||
-		int ret = parse_egress(a, &argc, &argv, tca_id, n);
+	    matches(*argv, "index") == 0) {
+		int ret = parse_direction(a, &argc, &argv, tca_id, n);
 
 		if (ret == 0) {
 			*argc_p = argc;
@@ -216,8 +234,6 @@ parse_mirred(struct action_util *a, int *argc_p, char ***argv_p,
 			return 0;
 		}
 
-	} else if (matches(*argv, "ingress") == 0) {
-		fprintf(stderr, "mirred ingress not supported at the moment\n");
 	} else if (matches(*argv, "help") == 0) {
 		usage();
 	} else {