Merge bitcoin/bitcoin#30202: netbase: extend CreateSock() to support creating arbitrary sockets

1245d1388b netbase: extend CreateSock() to support creating arbitrary sockets (Vasil Dimov)

Pull request description:

  Allow the callers of `CreateSock()` to pass all 3 arguments to the `socket(2)` syscall. This makes it possible to create sockets of any domain/type/protocol. In addition to extending arguments, some extra safety checks were put in place.

  The need for this came up during the discussion in https://github.com/bitcoin/bitcoin/pull/30043#discussion_r1618837102

ACKs for top commit:
  achow101:
    ACK 1245d1388b
  tdb3:
    re ACK 1245d1388b
  theStack:
    re-ACK 1245d1388b

Tree-SHA512: cc86b56121293ac98959aed0ed77812d20702ed7029b5a043586f46e74295779c5354bb0d5f9e80be6c29e535df980d34c1dbf609064fb7ea3e5ca0f0ed54d6b

src/test/fuzz/fuzz.cpp

@@ -101,8 +101,9 @@ void ResetCoverageCounters() {}
 
 void initialize()
 {
-    // Terminate immediately if a fuzzing harness ever tries to create a TCP socket.
-    CreateSock = [](const sa_family_t&) -> std::unique_ptr<Sock> { std::terminate(); };
+    // Terminate immediately if a fuzzing harness ever tries to create a socket.
+    // Individual tests can override this by pointing CreateSock to a mocked alternative.
+    CreateSock = [](int, int, int) -> std::unique_ptr<Sock> { std::terminate(); };
 
     // Terminate immediately if a fuzzing harness ever tries to perform a DNS lookup.
     g_dns_lookup = [](const std::string& name, bool allow_lookup) {

src/test/fuzz/i2p.cpp

@@ -27,7 +27,7 @@ FUZZ_TARGET(i2p, .init = initialize_i2p)
 
     // Mock CreateSock() to create FuzzedSock.
     auto CreateSockOrig = CreateSock;
-    CreateSock = [&fuzzed_data_provider](const sa_family_t&) {
+    CreateSock = [&fuzzed_data_provider](int, int, int) {
         return std::make_unique<FuzzedSock>(fuzzed_data_provider);
     };
 

src/test/i2p_tests.cpp

@@ -39,15 +39,14 @@ public:
 
 private:
     const BCLog::Level m_prev_log_level;
-    const std::function<std::unique_ptr<Sock>(const sa_family_t&)> m_create_sock_orig;
+    const decltype(CreateSock) m_create_sock_orig;
 };
 
 BOOST_FIXTURE_TEST_SUITE(i2p_tests, EnvTestingSetup)
 
 BOOST_AUTO_TEST_CASE(unlimited_recv)
 {
-    // Mock CreateSock() to create MockSock.
-    CreateSock = [](const sa_family_t&) {
+    CreateSock = [](int, int, int) {
         return std::make_unique<StaticContentsSock>(std::string(i2p::sam::MAX_MSG_SIZE + 1, 'a'));
     };
 
@@ -69,7 +68,7 @@ BOOST_AUTO_TEST_CASE(unlimited_recv)
 BOOST_AUTO_TEST_CASE(listen_ok_accept_fail)
 {
     size_t num_sockets{0};
-    CreateSock = [&num_sockets](const sa_family_t&) {
+    CreateSock = [&num_sockets](int, int, int) {
         // clang-format off
         ++num_sockets;
         // First socket is the control socket for creating the session.
@@ -133,9 +132,7 @@ BOOST_AUTO_TEST_CASE(listen_ok_accept_fail)
 
 BOOST_AUTO_TEST_CASE(damaged_private_key)
 {
-    const auto CreateSockOrig = CreateSock;
-
-    CreateSock = [](const sa_family_t&) {
+    CreateSock = [](int, int, int) {
         return std::make_unique<StaticContentsSock>("HELLO REPLY RESULT=OK VERSION=3.1\n"
                                                     "SESSION STATUS RESULT=OK DESTINATION=\n");
     };
@@ -172,8 +169,6 @@ BOOST_AUTO_TEST_CASE(damaged_private_key)
             BOOST_CHECK(!session.Connect(CService{}, conn, proxy_error));
         }
     }
-
-    CreateSock = CreateSockOrig;
 }
 
 BOOST_AUTO_TEST_SUITE_END()