Refactor existing TAP test cases to use the previously introduced
tuntap_helpers from tuntap_helpers.h for device setup, packet
construction, and cleanup.

This reduces code duplication, improves test maintainability, and
ensures consistent behavior across test scenarios.

Signed-off-by: Xu Du <[email protected]>
---
v1 -> v2:
  - Add mactap IFLA_ADDRESS attribute.
  - Fix incorrect argument order in build_eth and build_ipv4_header.

 tools/testing/selftests/net/tap.c | 281 +++++-------------------------
 1 file changed, 41 insertions(+), 240 deletions(-)

diff --git a/tools/testing/selftests/net/tap.c 
b/tools/testing/selftests/net/tap.c
index a0c9418132c8..6793e47d67a7 100644
--- a/tools/testing/selftests/net/tap.c
+++ b/tools/testing/selftests/net/tap.c
@@ -10,14 +10,13 @@
 #include <unistd.h>
 #include <net/if.h>
 #include <linux/if_tun.h>
-#include <linux/netlink.h>
-#include <linux/rtnetlink.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <linux/virtio_net.h>
 #include <netinet/ip.h>
 #include <netinet/udp.h>
 #include "kselftest_harness.h"
+#include "tuntap_helpers.h"
 
 static const char param_dev_tap_name[] = "xmacvtap0";
 static const char param_dev_dummy_name[] = "xdummy0";
@@ -26,161 +25,36 @@ static unsigned char param_hwaddr_dest[] = {
        0x00, 0xfe, 0x98, 0x94, 0xd2, 0x43
 };
 
-#define MAX_RTNL_PAYLOAD (2048)
-#define PKT_DATA 0xCB
-#define TEST_PACKET_SZ (sizeof(struct virtio_net_hdr) + ETH_HLEN + ETH_MAX_MTU)
-
-static struct rtattr *rtattr_add(struct nlmsghdr *nh, unsigned short type,
-                                unsigned short len)
-{
-       struct rtattr *rta =
-               (struct rtattr *)((uint8_t *)nh + RTA_ALIGN(nh->nlmsg_len));
-       rta->rta_type = type;
-       rta->rta_len = RTA_LENGTH(len);
-       nh->nlmsg_len = RTA_ALIGN(nh->nlmsg_len) + RTA_ALIGN(rta->rta_len);
-       return rta;
-}
-
-static struct rtattr *rtattr_begin(struct nlmsghdr *nh, unsigned short type)
-{
-       return rtattr_add(nh, type, 0);
-}
-
-static void rtattr_end(struct nlmsghdr *nh, struct rtattr *attr)
-{
-       uint8_t *end = (uint8_t *)nh + nh->nlmsg_len;
-
-       attr->rta_len = end - (uint8_t *)attr;
-}
-
-static struct rtattr *rtattr_add_str(struct nlmsghdr *nh, unsigned short type,
-                                    const char *s)
-{
-       unsigned int strsz = strlen(s) + 1;
-       struct rtattr *rta;
-
-       rta = rtattr_add(nh, type, strsz);
-
-       memcpy(RTA_DATA(rta), s, strsz);
-       return rta;
-}
-
-static struct rtattr *rtattr_add_any(struct nlmsghdr *nh, unsigned short type,
-                                    const void *arr, size_t len)
-{
-       struct rtattr *rta = rtattr_add(nh, type, len);
-
-       memcpy(RTA_DATA(rta), arr, len);
-       return rta;
-}
-
-static int dev_create(const char *dev, const char *link_type,
-                     int (*fill_rtattr)(struct nlmsghdr *nh),
-                     int (*fill_info_data)(struct nlmsghdr *nh))
-{
-       struct {
-               struct nlmsghdr nh;
-               struct ifinfomsg info;
-               unsigned char data[MAX_RTNL_PAYLOAD];
-       } req;
-       struct rtattr *link_info, *info_data;
-       int ret, rtnl;
-
-       rtnl = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
-       if (rtnl < 0) {
-               fprintf(stderr, "%s: socket %s\n", __func__, strerror(errno));
-               return 1;
-       }
-
-       memset(&req, 0, sizeof(req));
-       req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.info));
-       req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
-       req.nh.nlmsg_type = RTM_NEWLINK;
-
-       req.info.ifi_family = AF_UNSPEC;
-       req.info.ifi_type = 1;
-       req.info.ifi_index = 0;
-       req.info.ifi_flags = IFF_BROADCAST | IFF_UP;
-       req.info.ifi_change = 0xffffffff;
-
-       rtattr_add_str(&req.nh, IFLA_IFNAME, dev);
-
-       if (fill_rtattr) {
-               ret = fill_rtattr(&req.nh);
-               if (ret)
-                       return ret;
-       }
-
-       link_info = rtattr_begin(&req.nh, IFLA_LINKINFO);
-
-       rtattr_add_str(&req.nh, IFLA_INFO_KIND, link_type);
-
-       if (fill_info_data) {
-               info_data = rtattr_begin(&req.nh, IFLA_INFO_DATA);
-               ret = fill_info_data(&req.nh);
-               if (ret)
-                       return ret;
-               rtattr_end(&req.nh, info_data);
-       }
-
-       rtattr_end(&req.nh, link_info);
-
-       ret = send(rtnl, &req, req.nh.nlmsg_len, 0);
-       if (ret < 0)
-               fprintf(stderr, "%s: send %s\n", __func__, strerror(errno));
-       ret = (unsigned int)ret != req.nh.nlmsg_len;
-
-       close(rtnl);
-       return ret;
-}
-
-static int dev_delete(const char *dev)
-{
-       struct {
-               struct nlmsghdr nh;
-               struct ifinfomsg info;
-               unsigned char data[MAX_RTNL_PAYLOAD];
-       } req;
-       int ret, rtnl;
-
-       rtnl = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
-       if (rtnl < 0) {
-               fprintf(stderr, "%s: socket %s\n", __func__, strerror(errno));
-               return 1;
-       }
-
-       memset(&req, 0, sizeof(req));
-       req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(req.info));
-       req.nh.nlmsg_flags = NLM_F_REQUEST;
-       req.nh.nlmsg_type = RTM_DELLINK;
-
-       req.info.ifi_family = AF_UNSPEC;
-
-       rtattr_add_str(&req.nh, IFLA_IFNAME, dev);
+static struct in_addr param_ipaddr_src = {
+       __constant_htonl(0xac110002),
+};
 
-       ret = send(rtnl, &req, req.nh.nlmsg_len, 0);
-       if (ret < 0)
-               fprintf(stderr, "%s: send %s\n", __func__, strerror(errno));
+static struct in_addr param_ipaddr_dst = {
+       __constant_htonl(0xac110001),
+};
 
-       ret = (unsigned int)ret != req.nh.nlmsg_len;
+#define UDP_SRC_PORT 22
+#define UDP_DST_PORT 58822
+#define TEST_PACKET_SZ (sizeof(struct virtio_net_hdr) + ETH_HLEN + ETH_MAX_MTU)
 
-       close(rtnl);
-       return ret;
-}
+struct mactap_setup_config {
+       char name[IFNAMSIZ];
+       unsigned char hwaddr[ETH_ALEN];
+};
 
-static int macvtap_fill_rtattr(struct nlmsghdr *nh)
+static int macvtap_fill_rtattr(struct nlmsghdr *nh, void *data)
 {
+       struct mactap_setup_config *mactap = data;
        int ifindex;
 
-       ifindex = if_nametoindex(param_dev_dummy_name);
+       ifindex = if_nametoindex(mactap->name);
        if (ifindex == 0) {
                fprintf(stderr, "%s: ifindex  %s\n", __func__, strerror(errno));
                return -errno;
        }
 
        rtattr_add_any(nh, IFLA_LINK, &ifindex, sizeof(ifindex));
-       rtattr_add_any(nh, IFLA_ADDRESS, param_hwaddr_src, ETH_ALEN);
-
+       rtattr_add_any(nh, IFLA_ADDRESS, mactap->hwaddr, ETH_ALEN);
        return 0;
 }
 
@@ -212,91 +86,6 @@ static int opentap(const char *devname)
        return fd;
 }
 
-size_t build_eth(uint8_t *buf, uint16_t proto)
-{
-       struct ethhdr *eth = (struct ethhdr *)buf;
-
-       eth->h_proto = htons(proto);
-       memcpy(eth->h_source, param_hwaddr_src, ETH_ALEN);
-       memcpy(eth->h_dest, param_hwaddr_dest, ETH_ALEN);
-
-       return ETH_HLEN;
-}
-
-static uint32_t add_csum(const uint8_t *buf, int len)
-{
-       uint32_t sum = 0;
-       uint16_t *sbuf = (uint16_t *)buf;
-
-       while (len > 1) {
-               sum += *sbuf++;
-               len -= 2;
-       }
-
-       if (len)
-               sum += *(uint8_t *)sbuf;
-
-       return sum;
-}
-
-static uint16_t finish_ip_csum(uint32_t sum)
-{
-       uint16_t lo = sum & 0xffff;
-       uint16_t hi = sum >> 16;
-
-       return ~(lo + hi);
-
-}
-
-static uint16_t build_ip_csum(const uint8_t *buf, int len,
-                             uint32_t sum)
-{
-       sum += add_csum(buf, len);
-       return finish_ip_csum(sum);
-}
-
-static int build_ipv4_header(uint8_t *buf, int payload_len)
-{
-       struct iphdr *iph = (struct iphdr *)buf;
-
-       iph->ihl = 5;
-       iph->version = 4;
-       iph->ttl = 8;
-       iph->tot_len =
-               htons(sizeof(*iph) + sizeof(struct udphdr) + payload_len);
-       iph->id = htons(1337);
-       iph->protocol = IPPROTO_UDP;
-       iph->saddr = htonl((172 << 24) | (17 << 16) | 2);
-       iph->daddr = htonl((172 << 24) | (17 << 16) | 1);
-       iph->check = build_ip_csum(buf, iph->ihl << 2, 0);
-
-       return iph->ihl << 2;
-}
-
-static int build_udp_packet(uint8_t *buf, int payload_len, bool csum_off)
-{
-       const int ip4alen = sizeof(uint32_t);
-       struct udphdr *udph = (struct udphdr *)buf;
-       int len = sizeof(*udph) + payload_len;
-       uint32_t sum = 0;
-
-       udph->source = htons(22);
-       udph->dest = htons(58822);
-       udph->len = htons(len);
-
-       memset(buf + sizeof(struct udphdr), PKT_DATA, payload_len);
-
-       sum = add_csum(buf - 2 * ip4alen, 2 * ip4alen);
-       sum += htons(IPPROTO_UDP) + udph->len;
-
-       if (!csum_off)
-               sum += add_csum(buf, len);
-
-       udph->check = finish_ip_csum(sum);
-
-       return sizeof(*udph) + payload_len;
-}
-
 size_t build_test_packet_valid_udp_gso(uint8_t *buf, size_t payload_len)
 {
        uint8_t *cur = buf;
@@ -310,9 +99,12 @@ size_t build_test_packet_valid_udp_gso(uint8_t *buf, size_t 
payload_len)
        vh->gso_size = ETH_DATA_LEN - sizeof(struct iphdr);
        cur += sizeof(*vh);
 
-       cur += build_eth(cur, ETH_P_IP);
-       cur += build_ipv4_header(cur, payload_len);
-       cur += build_udp_packet(cur, payload_len, true);
+       cur += build_eth(cur, ETH_P_IP, param_hwaddr_src, param_hwaddr_dest);
+       cur += build_ipv4_header(cur, IPPROTO_UDP,
+                                payload_len + sizeof(struct udphdr),
+                                &param_ipaddr_src, &param_ipaddr_dst);
+       cur += build_udp_packet(cur, UDP_SRC_PORT, UDP_DST_PORT, payload_len,
+                               AF_INET, true);
 
        return cur - buf;
 }
@@ -326,9 +118,12 @@ size_t build_test_packet_valid_udp_csum(uint8_t *buf, 
size_t payload_len)
        vh->gso_type = VIRTIO_NET_HDR_GSO_NONE;
        cur += sizeof(*vh);
 
-       cur += build_eth(cur, ETH_P_IP);
-       cur += build_ipv4_header(cur, payload_len);
-       cur += build_udp_packet(cur, payload_len, false);
+       cur += build_eth(cur, ETH_P_IP, param_hwaddr_src, param_hwaddr_dest);
+       cur += build_ipv4_header(cur, IPPROTO_UDP,
+                                payload_len + sizeof(struct udphdr),
+                                &param_ipaddr_src, &param_ipaddr_dst);
+       cur += build_udp_packet(cur, UDP_SRC_PORT, UDP_DST_PORT, payload_len,
+                               AF_INET, false);
 
        return cur - buf;
 }
@@ -345,10 +140,13 @@ size_t 
build_test_packet_crash_tap_invalid_eth_proto(uint8_t *buf,
        vh->gso_size = ETH_DATA_LEN - sizeof(struct iphdr);
        cur += sizeof(*vh);
 
-       cur += build_eth(cur, 0);
+       cur += build_eth(cur, ETH_P_IP, param_hwaddr_src, param_hwaddr_dest);
        cur += sizeof(struct iphdr) + sizeof(struct udphdr);
-       cur += build_ipv4_header(cur, payload_len);
-       cur += build_udp_packet(cur, payload_len, true);
+       cur += build_ipv4_header(cur, IPPROTO_UDP,
+                                payload_len + sizeof(struct udphdr),
+                                &param_ipaddr_src, &param_ipaddr_dst);
+       cur += build_udp_packet(cur, UDP_SRC_PORT, UDP_DST_PORT, payload_len,
+                               AF_INET, true);
        cur += payload_len;
 
        return cur - buf;
@@ -362,12 +160,15 @@ FIXTURE(tap)
 FIXTURE_SETUP(tap)
 {
        int ret;
+       struct mactap_setup_config mactap_config;
 
-       ret = dev_create(param_dev_dummy_name, "dummy", NULL, NULL);
+       ret = dev_create(param_dev_dummy_name, "dummy", NULL, NULL, NULL);
        EXPECT_EQ(ret, 0);
 
+       strcpy(mactap_config.name, param_dev_dummy_name);
+       memcpy(mactap_config.hwaddr, param_hwaddr_src, ETH_ALEN);
        ret = dev_create(param_dev_tap_name, "macvtap", macvtap_fill_rtattr,
-                        NULL);
+                        NULL, &mactap_config);
        EXPECT_EQ(ret, 0);
 
        self->fd = opentap(param_dev_tap_name);
-- 
2.49.0


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