selftests: net/psock_fanout: socket joins fanout when link is down

Modify test_control_group to have toggle parameter.
When toggle is non-zero, loopback device will be set down for the
initialization of fd[1] which is still expected to successfully join
the fanout.

Signed-off-by: Gur Stavi <[e-mail]>
Reviewed-by: Willem de Bruijn <[e-mail]>
Link: https://patch.msgid.link/6[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/psock_fanout.c

···
 #include <string.h>
 #include <sys/mman.h>
 #include <sys/socket.h>
+#include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
···
 #define RING_NUM_FRAMES			20
 
 static uint32_t cfg_max_num_members;
+
+static void loopback_set_up_down(int state_up)
+{
+	struct ifreq ifreq = {};
+	int fd, err;
+
+	fd = socket(AF_PACKET, SOCK_RAW, 0);
+	if (fd < 0) {
+		perror("socket loopback");
+		exit(1);
+	}
+	strcpy(ifreq.ifr_name, "lo");
+	err = ioctl(fd, SIOCGIFFLAGS, &ifreq);
+	if (err) {
+		perror("SIOCGIFFLAGS");
+		exit(1);
+	}
+	if (state_up != !!(ifreq.ifr_flags & IFF_UP)) {
+		ifreq.ifr_flags ^= IFF_UP;
+		err = ioctl(fd, SIOCSIFFLAGS, &ifreq);
+		if (err) {
+			perror("SIOCSIFFLAGS");
+			exit(1);
+		}
+	}
+	close(fd);
+}
 
 /* Open a socket in a given fanout mode.
  * @return -1 if mode is bad, a valid socket otherwise */
···
 }
 
 /* Test illegal group with different modes or flags */
-static void test_control_group(void)
+static void test_control_group(int toggle)
 {
 	int fds[2];
 
-	fprintf(stderr, "test: control multiple sockets\n");
+	if (toggle)
+		fprintf(stderr, "test: control multiple sockets with link down toggle\n");
+	else
+		fprintf(stderr, "test: control multiple sockets\n");
 
 	fds[0] = sock_fanout_open(PACKET_FANOUT_HASH, 0);
 	if (fds[0] == -1) {
 		fprintf(stderr, "ERROR: failed to open HASH socket\n");
 		exit(1);
 	}
+	if (toggle)
+		loopback_set_up_down(0);
 	if (sock_fanout_open(PACKET_FANOUT_HASH |
 			       PACKET_FANOUT_FLAG_DEFRAG, 0) != -1) {
 		fprintf(stderr, "ERROR: joined group with wrong flag defrag\n");
···
 		fprintf(stderr, "ERROR: failed to join group\n");
 		exit(1);
 	}
+	if (toggle)
+		loopback_set_up_down(1);
 	if (close(fds[1]) || close(fds[0])) {
 		fprintf(stderr, "ERROR: closing sockets\n");
 		exit(1);
···
 	int port_off = 2, tries = 20, ret;
 
 	test_control_single();
-	test_control_group();
+	test_control_group(0);
+	test_control_group(1);
 	test_control_group_max_num_members();
 	test_unique_fanout_group_ids();