Use socket address functions in unbound IPv4 UDP tests.

Also switch to the correct casing style for local address variables.

PiperOrigin-RevId: 233161128
Change-Id: Ibc4a10a5d3ab04c40907aa885e8237b255c65a79

1 files changed, 166 insertions, 179 deletions

diff --git a/test/syscalls/linux/socket_ipv4_udp_unbound.cc b/test/syscalls/linux/socket_ipv4_udp_unbound.cc
index 1b47139e4..4058324a2 100644
--- a/test/syscalls/linux/socket_ipv4_udp_unbound.cc
+++ b/test/syscalls/linux/socket_ipv4_udp_unbound.cc
@@ -29,6 +29,17 @@
 namespace gvisor {
 namespace testing {
 
+constexpr char kMulticastAddress[] = "224.0.2.1";
+
+TestAddress V4Multicast() {
+  TestAddress t("V4Multicast");
+  t.addr.ss_family = AF_INET;
+  t.addr_len = sizeof(sockaddr_in);
+  reinterpret_cast<sockaddr_in*>(&t.addr)->sin_addr.s_addr =
+      inet_addr(kMulticastAddress);
+  return t;
+}
+
 // Check that packets are not received without a group memebership. Default send
 // interface configured by bind.
 TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackNoGroup) {
@@ -36,41 +47,37 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackNoGroup) {
 
   // Bind the first FD to the loopback. This is an alternative to
   // IP_MULTICAST_IF for setting the default send interface.
-  sockaddr_in senderAddr = {};
-  senderAddr.sin_family = AF_INET;
-  senderAddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  auto sender_addr = V4Loopback();
   EXPECT_THAT(
-      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&senderAddr),
-           sizeof(senderAddr)),
+      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
       SyscallSucceeds());
 
   // Bind the second FD to the v4 any address. If multicast worked like unicast,
   // this would ensure that we get the packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Send the multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
 
   // Check that we did not receive the multicast packet.
   char recv_buf[sizeof(send_buf)] = {};
@@ -86,39 +93,37 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackAddrNoDefaultSendIf) {
 
   // Bind the second FD to the v4 any address to ensure that we can receive any
   // unicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register to receive multicast packets.
   ip_mreq group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_interface.s_addr = htonl(INADDR_LOOPBACK);
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallFailsWithErrno(ENETUNREACH));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallFailsWithErrno(ENETUNREACH));
 }
 
 // Check that not setting a default send interface prevents multicast packets
@@ -128,39 +133,37 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackNicNoDefaultSendIf) {
 
   // Bind the second FD to the v4 any address to ensure that we can receive any
   // unicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register to receive multicast packets.
   ip_mreqn group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_ifindex = ASSERT_NO_ERRNO_AND_VALUE(InterfaceIndex("lo"));
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallFailsWithErrno(ENETUNREACH));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallFailsWithErrno(ENETUNREACH));
 }
 
 // Check that multicast works when the default send interface is configured by
@@ -170,49 +173,45 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackAddr) {
 
   // Bind the first FD to the loopback. This is an alternative to
   // IP_MULTICAST_IF for setting the default send interface.
-  sockaddr_in senderAddr = {};
-  senderAddr.sin_family = AF_INET;
-  senderAddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  auto sender_addr = V4Loopback();
   EXPECT_THAT(
-      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&senderAddr),
-           sizeof(senderAddr)),
+      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
       SyscallSucceeds());
 
   // Bind the second FD to the v4 any address to ensure that we can receive the
   // multicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register to receive multicast packets.
   ip_mreq group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_interface.s_addr = htonl(INADDR_LOOPBACK);
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
 
   // Check that we received the multicast packet.
   char recv_buf[sizeof(send_buf)] = {};
@@ -230,49 +229,45 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastLoopbackNic) {
 
   // Bind the first FD to the loopback. This is an alternative to
   // IP_MULTICAST_IF for setting the default send interface.
-  sockaddr_in senderAddr = {};
-  senderAddr.sin_family = AF_INET;
-  senderAddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  auto sender_addr = V4Loopback();
   EXPECT_THAT(
-      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&senderAddr),
-           sizeof(senderAddr)),
+      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
       SyscallSucceeds());
 
   // Bind the second FD to the v4 any address to ensure that we can receive the
   // multicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register to receive multicast packets.
   ip_mreqn group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_ifindex = ASSERT_NO_ERRNO_AND_VALUE(InterfaceIndex("lo"));
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
 
   // Check that we received the multicast packet.
   char recv_buf[sizeof(send_buf)] = {};
@@ -289,7 +284,7 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastInvalidDrop) {
 
   // Unregister from a membership that we didn't have.
   ip_mreq group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_interface.s_addr = htonl(INADDR_LOOPBACK);
   EXPECT_THAT(setsockopt(sockets->first_fd(), IPPROTO_IP, IP_DROP_MEMBERSHIP,
                          &group, sizeof(group)),
@@ -304,33 +299,29 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastDropAddr) {
 
   // Bind the first FD to the loopback. This is an alternative to
   // IP_MULTICAST_IF for setting the default send interface.
-  sockaddr_in senderAddr = {};
-  senderAddr.sin_family = AF_INET;
-  senderAddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  auto sender_addr = V4Loopback();
   EXPECT_THAT(
-      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&senderAddr),
-           sizeof(senderAddr)),
+      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
       SyscallSucceeds());
 
   // Bind the second FD to the v4 any address to ensure that we can receive the
   // multicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register and unregister to receive multicast packets.
   ip_mreq group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_interface.s_addr = htonl(INADDR_LOOPBACK);
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
@@ -340,16 +331,16 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastDropAddr) {
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
 
   // Check that we did not receive the multicast packet.
   char recv_buf[sizeof(send_buf)] = {};
@@ -366,33 +357,29 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastDropNic) {
 
   // Bind the first FD to the loopback. This is an alternative to
   // IP_MULTICAST_IF for setting the default send interface.
-  sockaddr_in senderAddr = {};
-  senderAddr.sin_family = AF_INET;
-  senderAddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+  auto sender_addr = V4Loopback();
   EXPECT_THAT(
-      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&senderAddr),
-           sizeof(senderAddr)),
+      bind(sockets->first_fd(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
       SyscallSucceeds());
 
   // Bind the second FD to the v4 any address to ensure that we can receive the
   // multicast packet.
-  sockaddr_in receiverAddr = {};
-  receiverAddr.sin_family = AF_INET;
-  receiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
-  EXPECT_THAT(
-      bind(sockets->second_fd(), reinterpret_cast<sockaddr*>(&receiverAddr),
-           sizeof(receiverAddr)),
-      SyscallSucceeds());
-  socklen_t receiverAddrLen = sizeof(receiverAddr);
-  EXPECT_THAT(
-      getsockname(sockets->second_fd(),
-                  reinterpret_cast<sockaddr*>(&receiverAddr), &receiverAddrLen),
-      SyscallSucceeds());
-  EXPECT_EQ(receiverAddrLen, sizeof(receiverAddr));
+  auto receiver_addr = V4Any();
+  EXPECT_THAT(bind(sockets->second_fd(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  EXPECT_THAT(getsockname(sockets->second_fd(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
 
   // Register and unregister to receive multicast packets.
   ip_mreqn group = {};
-  group.imr_multiaddr.s_addr = inet_addr("224.0.2.1");
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
   group.imr_ifindex = ASSERT_NO_ERRNO_AND_VALUE(InterfaceIndex("lo"));
   EXPECT_THAT(setsockopt(sockets->second_fd(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
                          &group, sizeof(group)),
@@ -402,16 +389,16 @@ TEST_P(IPv4UDPUnboundSocketPairTest, IpMulticastDropNic) {
               SyscallSucceeds());
 
   // Send a multicast packet.
-  sockaddr_in sendAddr = {};
-  sendAddr.sin_family = AF_INET;
-  sendAddr.sin_port = receiverAddr.sin_port;
-  sendAddr.sin_addr.s_addr = inet_addr("224.0.2.1");
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
   char send_buf[200];
   RandomizeBuffer(send_buf, sizeof(send_buf));
-  EXPECT_THAT(RetryEINTR(sendto)(
-                  sockets->first_fd(), send_buf, sizeof(send_buf), 0,
-                  reinterpret_cast<sockaddr*>(&sendAddr), sizeof(sendAddr)),
-              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_THAT(
+      RetryEINTR(sendto)(sockets->first_fd(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
 
   // Check that we did not receive the multicast packet.
   char recv_buf[sizeof(send_buf)] = {};