iptables: refactor to make targets extendable

Like matchers, targets should use a module-like register/lookup system. This
replaces the brittle switch statements we had before.

The only behavior change is supporing IPT_GET_REVISION_TARGET. This makes it
much easier to add IPv6 redirect in the next change.

Updates #3549.

PiperOrigin-RevId: 334469418

1 files changed, 32 insertions, 0 deletions

diff --git a/test/syscalls/linux/ip6tables.cc b/test/syscalls/linux/ip6tables.cc
index 97297ee2b..f08f2dc55 100644
--- a/test/syscalls/linux/ip6tables.cc
+++ b/test/syscalls/linux/ip6tables.cc
@@ -82,6 +82,38 @@ TEST(IP6TablesBasic, GetEntriesErrorPrecedence) {
       SyscallFailsWithErrno(EINVAL));
 }
 
+TEST(IP6TablesBasic, GetRevision) {
+  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_NET_RAW)));
+
+  int sock;
+  ASSERT_THAT(sock = socket(AF_INET6, SOCK_RAW, IPPROTO_RAW),
+              SyscallSucceeds());
+
+  struct xt_get_revision rev = {
+      .name = "REDIRECT",
+      .revision = 0,
+  };
+  socklen_t rev_len = sizeof(rev);
+
+  // TODO(gvisor.dev/issue/3549): IPv6 redirect support.
+  const int retval =
+      getsockopt(sock, SOL_IPV6, IP6T_SO_GET_REVISION_TARGET, &rev, &rev_len);
+  if (IsRunningOnGvisor()) {
+    EXPECT_THAT(retval, SyscallFailsWithErrno(ENOPROTOOPT));
+    return;
+  }
+
+  // Revision 0 exists.
+  EXPECT_THAT(retval, SyscallSucceeds());
+  EXPECT_EQ(rev.revision, 0);
+
+  // Revisions > 0 don't exist.
+  rev.revision = 1;
+  EXPECT_THAT(
+      getsockopt(sock, SOL_IPV6, IP6T_SO_GET_REVISION_TARGET, &rev, &rev_len),
+      SyscallFailsWithErrno(EPROTONOSUPPORT));
+}
+
 // This tests the initial state of a machine with empty ip6tables via
 // getsockopt(IP6T_SO_GET_INFO). We don't have a guarantee that the iptables are
 // empty when running in native, but we can test that gVisor has the same