Add support for IPv6 environment for napi_id test.

Test Plan:

    ./run_kselftest.sh -t drivers/net:napi_id.py
    TAP version 13
    1..1
    # timeout set to 45
    # selftests: drivers/net: napi_id.py
    # TAP version 13
    # 1..1
    # ok 1 napi_id.test_napi_id
    # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
    ok 1 selftests: drivers/net: napi_id.py

Signed-off-by: Tianyi Cui <1997cui@gmail.com>
---
Changelog:
 v2:
   - Use cfg.addr instead of if statement in napi_id.py
 v1: https://lore.kernel.org/all/20250715212349.2308385-1-1997cui@gmail.com/

 .../testing/selftests/drivers/net/napi_id.py  |  4 +--
 .../selftests/drivers/net/napi_id_helper.c    | 35 ++++++++++++++-----
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/napi_id.py b/tools/testing/selftests/drivers/net/napi_id.py
index 356bac46ba04..d05eddcad539 100755
--- a/tools/testing/selftests/drivers/net/napi_id.py
+++ b/tools/testing/selftests/drivers/net/napi_id.py
@@ -7,10 +7,10 @@ from lib.py import bkg, cmd, rand_port, NetNSEnter

 def test_napi_id(cfg) -> None:
     port = rand_port()
-    listen_cmd = f"{cfg.test_dir}/napi_id_helper {cfg.addr_v['4']} {port}"
+    listen_cmd = f"{cfg.test_dir}/napi_id_helper {cfg.addr} {port}"

     with bkg(listen_cmd, ksft_wait=3) as server:
-        cmd(f"echo a | socat - TCP:{cfg.addr_v['4']}:{port}", host=cfg.remote, shell=True)
+        cmd(f"echo a | socat - TCP:{cfg.baddr}:{port}", host=cfg.remote, shell=True)

     ksft_eq(0, server.ret)

diff --git a/tools/testing/selftests/drivers/net/napi_id_helper.c b/tools/testing/selftests/drivers/net/napi_id_helper.c
index eecd610c2109..7f49ca6c8637 100644
--- a/tools/testing/selftests/drivers/net/napi_id_helper.c
+++ b/tools/testing/selftests/drivers/net/napi_id_helper.c
@@ -7,41 +7,58 @@
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>
+#include <netdb.h>

 #include "../../net/lib/ksft.h"

 int main(int argc, char *argv[])
 {
-	struct sockaddr_in address;
+	struct sockaddr_storage address;
+	struct addrinfo *result;
+	struct addrinfo hints;
 	unsigned int napi_id;
-	unsigned int port;
+	socklen_t addr_len;
 	socklen_t optlen;
 	char buf[1024];
 	int opt = 1;
+	int family;
 	int server;
 	int client;
 	int ret;

-	server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_flags = AI_PASSIVE;
+
+	ret = getaddrinfo(argv[1], argv[2], &hints, &result);
+	if (ret != 0) {
+		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(ret));
+		return 1;
+	}
+
+	family = result->ai_family;
+	addr_len = result->ai_addrlen;
+
+	server = socket(family, SOCK_STREAM, IPPROTO_TCP);
 	if (server < 0) {
 		perror("socket creation failed");
+		freeaddrinfo(result);
 		if (errno == EAFNOSUPPORT)
 			return -1;
 		return 1;
 	}

-	port = atoi(argv[2]);
-
 	if (setsockopt(server, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt))) {
 		perror("setsockopt");
+		freeaddrinfo(result);
 		return 1;
 	}

-	address.sin_family = AF_INET;
-	inet_pton(AF_INET, argv[1], &address.sin_addr);
-	address.sin_port = htons(port);
+	memcpy(&address, result->ai_addr, result->ai_addrlen);
+	freeaddrinfo(result);

-	if (bind(server, (struct sockaddr *)&address, sizeof(address)) < 0) {
+	if (bind(server, (struct sockaddr *)&address, addr_len) < 0) {
 		perror("bind failed");
 		return 1;
 	}
--
2.47.1