packet03: pass MAC addresses to xdp_prog_user as arguments

Instead of running a sudo command from the xdp_prog_user program, do pass MAC
addresses as parameters.  Add a new set_redirect_map command to the testenv.sh
script which simplifies the process of calling the xdp_prog_user for this purpose.
Update the readme correspondingly.

Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>

Author: aspsk

common/common_defines.h

@@ -12,6 +12,8 @@ struct config {
 	bool do_unload;
 	char filename[512];
 	char progsec[32];
+	char src_mac[18];
+	char dest_mac[18];
 };
 
 /* Defined in common_params.o */

common/common_params.c

@@ -91,7 +91,7 @@ void parse_cmdline_args(int argc, char **argv,
 	}
 
 	/* Parse commands line args */
-	while ((opt = getopt_long(argc, argv, "hd:r:ASNFUq",
+	while ((opt = getopt_long(argc, argv, "hd:r:L:R:ASNFUq",
 				  long_options, &longindex)) != -1) {
 		switch (opt) {
 		case 'd':
@@ -159,6 +159,14 @@ void parse_cmdline_args(int argc, char **argv,
 		case 'h':
 			full_help = true;
 			/* fall-through */
+		case 'L': /* --src-mac */
+			dest  = (char *)&cfg->src_mac;
+			strncpy(dest, optarg, sizeof(cfg->src_mac));
+			break;
+		case 'R': /* --dest-mac */
+			dest  = (char *)&cfg->dest_mac;
+			strncpy(dest, optarg, sizeof(cfg->dest_mac));
+			break;
 		error:
 		default:
 			usage(argv[0], doc, options_wrapper, full_help);

packet-solutions/xdp_prog_user.c

@@ -38,57 +38,52 @@ static const struct option_wrapper long_options[] = {
 	{{"redirect-dev",         required_argument,	NULL, 'r' },
 	 "Redirect to device <ifname>", "<ifname>", true},
 
+	{{"src-mac", required_argument, NULL, 'L' },
+	 "Source MAC address of <dev>", "<mac>", true },
+
+	{{"dest-mac", required_argument, NULL, 'R' },
+	 "Destination MAC address of <redirect-dev>", "<mac>", true },
+
 	{{"quiet",       no_argument,		NULL, 'q' },
 	 "Quiet mode (no output)"},
 
 	{{0, 0, NULL,  0 }, NULL, false}
 };
 
-static void read_output(const char *cmd, char *str, size_t str_size)
+static int parse_u8(char *str, unsigned char *x)
 {
-	FILE *f = popen(cmd, "r");
-	if (!f) {
-		fprintf(stderr, "can't execute %s", cmd);
-		exit(EXIT_FAILURE);
-	}
+	unsigned long z;
 
-	if (fgets(str, str_size, f) == NULL) {
-		fprintf(stderr, "can't read from popen(%s)", cmd);
-		exit(EXIT_FAILURE);
-	}
+	z = strtoul(str, 0, 16);
+	if (z > 0xff)
+		return -1;
 
-	pclose(f);
-}
+	if (x)
+		*x = z;
 
-static void parse_mac(char *str, unsigned char mac[ETH_ALEN])
-{
-	mac[0] = strtoul(str,    0, 16);
-	mac[1] = strtoul(str+3,  0, 16);
-	mac[2] = strtoul(str+6,  0, 16);
-	mac[3] = strtoul(str+9,  0, 16);
-	mac[4] = strtoul(str+12, 0, 16);
-	mac[5] = strtoul(str+15, 0, 16);
+	return 0;
 }
 
-static void veth_inner_mac(const char *ifname, unsigned char mac[ETH_ALEN])
+static int parse_mac(char *str, unsigned char mac[ETH_ALEN])
 {
-	char str[64];
-	char cmd[128];
-	const char *fmt = "sudo ip netns exec %s cat /sys/class/net/veth0/address";
+	if (parse_u8(str, &mac[0]) < 0)
+		return -1;
+	if (parse_u8(str + 3, &mac[1]) < 0)
+		return -1;
+	if (parse_u8(str + 6, &mac[2]) < 0)
+		return -1;
+	if (parse_u8(str + 9, &mac[3]) < 0)
+		return -1;
+	if (parse_u8(str + 12, &mac[4]) < 0)
+		return -1;
+	if (parse_u8(str + 15, &mac[5]) < 0)
+		return -1;
 
-	snprintf(cmd, sizeof(cmd), fmt, ifname);
-	read_output(cmd, str, sizeof(str));
-	parse_mac(str, mac);
+	return 0;
 }
 
-static int write_iface_params(int map_fd, struct config *cfg)
+static int write_iface_params(int map_fd, unsigned char *src, unsigned char *dest)
 {
-	unsigned char src[ETH_ALEN];
-	unsigned char dest[ETH_ALEN];
-
-	veth_inner_mac(cfg->ifname, src);
-	veth_inner_mac(cfg->redirect_ifname, dest);
-
 	if (bpf_map_update_elem(map_fd, src, dest, 0) < 0) {
 		fprintf(stderr,
 			"WARN: Failed to update bpf map file: err(%d):%s\n",
@@ -138,6 +133,8 @@ int main(int argc, char **argv)
 	int map_fd;
 	bool redirect_map;
 	char pin_dir[PATH_MAX];
+	unsigned char src[ETH_ALEN];
+	unsigned char dest[ETH_ALEN];
 
 	struct config cfg = {
 		.ifindex   = -1,
@@ -161,6 +158,16 @@ int main(int argc, char **argv)
 		return EXIT_FAIL_OPTION;
 	}
 
+	if (parse_mac(cfg.src_mac, src) < 0) {
+		fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.src_mac);
+		return EXIT_FAIL_OPTION;
+	}
+
+	if (parse_mac(cfg.dest_mac, dest) < 0) {
+		fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.dest_mac);
+		return EXIT_FAIL_OPTION;
+	}
+
 	/* Open the tx_port map corresponding to the cfg.ifname interface */
 	map_fd = open_bpf_map_file(pin_dir, "tx_port");
 	if (map_fd < 0) {
@@ -182,7 +189,7 @@ int main(int argc, char **argv)
 		}
 
 		/* Setup the mapping containing MAC addresses */
-		if (write_iface_params(map_fd, &cfg) < 0) {
+		if (write_iface_params(map_fd, src, dest) < 0) {
 			fprintf(stderr, "can't write iface params\n");
 			return 1;
 		}

packet03-redirecting/README.org

@@ -176,10 +176,12 @@ To test the code, configure environment as in the Assignment 2 and install the
 $ sudo ./xdp_loader -d left -F --progsec xdp_redirect_map --skb
 $ sudo ./xdp_loader -d right -F --progsec xdp_redirect_map --skb
 #+end_src
-Configure parameters for both interfaces using the new =xdp_prog_user= helper:
+Configure parameters for both interfaces using the new =xdp_prog_user= helper.
+For simplicity there is a new special helper, =t set_redirect_map=, which will
+do the work for you.  See its implementation to see how it obtains inner MAC
+addresses by interface names.
 #+begin_src sh
-$ sudo ./xdp_prog_user -d left -r right
-$ sudo ./xdp_prog_user -d right -r left
+$ t set_redirect_map right left
 #+end_src
 Pings between the two inner interfaces should pass now. Check that they are
 actually forwarded by our programs by running =xdp_stats= on both interfaces:

packet03-redirecting/xdp_prog_user.c

@@ -38,26 +38,26 @@ static const struct option_wrapper long_options[] = {
 	{{"redirect-dev",         required_argument,	NULL, 'r' },
 	 "Redirect to device <ifname>", "<ifname>", true},
 
+	{{"src-mac", required_argument, NULL, 'L' },
+	 "Source MAC address of <dev>", "<mac>", true },
+
+	{{"dest-mac", required_argument, NULL, 'R' },
+	 "Destination MAC address of <redirect-dev>", "<mac>", true },
+
 	{{"quiet",       no_argument,		NULL, 'q' },
 	 "Quiet mode (no output)"},
 
 	{{0, 0, NULL,  0 }, NULL, false}
 };
 
-static void veth_inner_mac(const char *ifname, unsigned char mac[ETH_ALEN])
+static int parse_mac(char *str, unsigned char mac[ETH_ALEN])
 {
-	/* Assignment 3: put the MAC address of the ifname's veth peer device
-	 * to the mac array */
+	/* Assignment 3: parse a MAC address in this function and place the
+	 * result in the mac array */
 }
 
-static int write_iface_params(int map_fd, struct config *cfg)
+static int write_iface_params(int map_fd, unsigned char *src, unsigned char *dest)
 {
-	unsigned char src[ETH_ALEN];
-	unsigned char dest[ETH_ALEN];
-
-	veth_inner_mac(cfg->ifname, src);
-	veth_inner_mac(cfg->redirect_ifname, dest);
-
 	if (bpf_map_update_elem(map_fd, src, dest, 0) < 0) {
 		fprintf(stderr,
 			"WARN: Failed to update bpf map file: err(%d):%s\n",
@@ -86,6 +86,8 @@ int main(int argc, char **argv)
 	int map_fd;
 	bool redirect_map;
 	char pin_dir[PATH_MAX];
+	unsigned char src[ETH_ALEN];
+	unsigned char dest[ETH_ALEN];
 
 	struct config cfg = {
 		.ifindex   = -1,
@@ -109,6 +111,17 @@ int main(int argc, char **argv)
 		return EXIT_FAIL_OPTION;
 	}
 
+	if (parse_mac(cfg.src_mac, src) < 0) {
+		fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.src_mac);
+		return EXIT_FAIL_OPTION;
+	}
+
+	if (parse_mac(cfg.dest_mac, dest) < 0) {
+		fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.dest_mac);
+		return EXIT_FAIL_OPTION;
+	}
+
+
 	/* Assignment 3: open the tx_port map corresponding to the cfg.ifname interface */
 	map_fd = -1;
 
@@ -124,7 +137,7 @@ int main(int argc, char **argv)
 		map_fd = -1;
 
 		/* Setup the mapping containing MAC addresses */
-		if (write_iface_params(map_fd, &cfg) < 0) {
+		if (write_iface_params(map_fd, src, dest) < 0) {
 			fprintf(stderr, "can't write iface params\n");
 			return 1;
 		}

testenv/testenv.sh

@@ -400,6 +400,23 @@ print_alias()
     echo "alias t='$sudo$scriptname'"
 }
 
+#
+# This command can be used to set maps for the assignment 3 of the
+# packet03-redirecting lesson. It takes two arguments: the source and the
+# destination interface names.
+#
+set_redirect_map()
+{
+    local src="$1"
+    local dest="$2"
+    local src_mac=$(ip netns exec $src cat /sys/class/net/veth0/address)
+    local dest_mac=$(ip netns exec $dest cat /sys/class/net/veth0/address)
+
+    # set bidirectional forwarding
+    ./xdp_prog_user -d $src -r $dest --src-mac $src_mac --dest-mac $dest_mac
+    ./xdp_prog_user -d $dest -r $src --src-mac $dest_mac --dest-mac $src_mac
+}
+
 xdp_load()
 {
     get_nsname && ensure_nsname
@@ -443,6 +460,7 @@ usage()
     echo "unload              Unload XDP program on outer interface"
     echo "tcpdump             Run on outer interface (or inner with --inner)"
     echo "stats               Run the XDP statistics program"
+    echo "set_redirect_map    Setup redirect maps for packet03 lessons"
     echo ""
 
     if [ -z "$FULL" ] ; then
@@ -552,6 +570,10 @@ case "$1" in
     ping|tcpdump)
         CMD="run_$1"
         ;;
+    set_redirect_map)
+        CMD="set_redirect_map $2 $3"
+        shift 2
+        ;;
     "alias")
         print_alias
         exit 0