selftests/net: udpgso_bench_tx: fix dst ip argument

udpgso_bench_tx call setup_sockaddr() for dest address before
parsing all arguments, if we specify "-p ${dst_port}" after "-D ${dst_ip}",
then ${dst_port} will be ignored, and using default cfg_port 8000.

This will cause test case "multiple GRO socks" failed in udpgro.sh.

Setup sockaddr after parsing all arguments.

Fixes: 3a687be ("selftests: udp gso benchmark")
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/ff620d9f-5b52-06ab-5286-44b945453002@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/udpgso_bench_tx.c

@@ -419,6 +419,7 @@ static void usage(const char *filepath)
 
 static void parse_opts(int argc, char **argv)
 {
+	const char *bind_addr = NULL;
 	int max_len, hdrlen;
 	int c;
 
@@ -446,7 +447,7 @@ static void parse_opts(int argc, char **argv)
 			cfg_cpu = strtol(optarg, NULL, 0);
 			break;
 		case 'D':
-			setup_sockaddr(cfg_family, optarg, &cfg_dst_addr);
+			bind_addr = optarg;
 			break;
 		case 'l':
 			cfg_runtime_ms = strtoul(optarg, NULL, 10) * 1000;
@@ -492,6 +493,11 @@ static void parse_opts(int argc, char **argv)
 		}
 	}
 
+	if (!bind_addr)
+		bind_addr = cfg_family == PF_INET6 ? "::" : "0.0.0.0";
+
+	setup_sockaddr(cfg_family, bind_addr, &cfg_dst_addr);
+
 	if (optind != argc)
 		usage(argv[0]);