net: add new method Sock::Listen() that wraps listen()

This will help to increase `Sock` usage and make more code mockable.

src/test/fuzz/util.cpp

@@ -180,6 +180,25 @@ int FuzzedSock::Bind(const sockaddr*, socklen_t) const
     return 0;
 }
 
+int FuzzedSock::Listen(int) const
+{
+    // Have a permanent error at listen_errnos[0] because when the fuzzed data is exhausted
+    // SetFuzzedErrNo() will always set the global errno to listen_errnos[0]. We want to
+    // avoid this method returning -1 and setting errno to a temporary error (like EAGAIN)
+    // repeatedly because proper code should retry on temporary errors, leading to an
+    // infinite loop.
+    constexpr std::array listen_errnos{
+        EADDRINUSE,
+        EINVAL,
+        EOPNOTSUPP,
+    };
+    if (m_fuzzed_data_provider.ConsumeBool()) {
+        SetFuzzedErrNo(m_fuzzed_data_provider, listen_errnos);
+        return -1;
+    }
+    return 0;
+}
+
 std::unique_ptr<Sock> FuzzedSock::Accept(sockaddr* addr, socklen_t* addr_len) const
 {
     constexpr std::array accept_errnos{

src/test/fuzz/util.h

@@ -66,6 +66,8 @@ public:
 
     int Bind(const sockaddr*, socklen_t) const override;
 
+    int Listen(int backlog) const override;
+
     std::unique_ptr<Sock> Accept(sockaddr* addr, socklen_t* addr_len) const override;
 
     int GetSockOpt(int level, int opt_name, void* opt_val, socklen_t* opt_len) const override;