net: add new method Sock::Bind() that wraps bind()

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

src/net.cpp

@@ -2396,8 +2396,7 @@ bool CConnman::BindListenPort(const CService& addrBind, bilingual_str& strError,
 #endif
     }
 
-    if (::bind(sock->Get(), (struct sockaddr*)&sockaddr, len) == SOCKET_ERROR)
-    {
+    if (sock->Bind(reinterpret_cast<struct sockaddr*>(&sockaddr), len) == SOCKET_ERROR) {
         int nErr = WSAGetLastError();
         if (nErr == WSAEADDRINUSE)
             strError = strprintf(_("Unable to bind to %s on this computer. %s is probably already running."), addrBind.ToString(), PACKAGE_NAME);

src/test/fuzz/util.cpp

@@ -160,6 +160,26 @@ int FuzzedSock::Connect(const sockaddr*, socklen_t) const
     return 0;
 }
 
+int FuzzedSock::Bind(const sockaddr*, socklen_t) const
+{
+    // Have a permanent error at bind_errnos[0] because when the fuzzed data is exhausted
+    // SetFuzzedErrNo() will always set the global errno to bind_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 bind_errnos{
+        EACCES,
+        EADDRINUSE,
+        EADDRNOTAVAIL,
+        EAGAIN,
+    };
+    if (m_fuzzed_data_provider.ConsumeBool()) {
+        SetFuzzedErrNo(m_fuzzed_data_provider, bind_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

@@ -64,6 +64,8 @@ public:
 
     int Connect(const sockaddr*, socklen_t) const override;
 
+    int Bind(const sockaddr*, socklen_t) 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;

src/test/util/net.h

@@ -127,6 +127,8 @@ public:
 
     int Connect(const sockaddr*, socklen_t) const override { return 0; }
 
+    int Bind(const sockaddr*, socklen_t) const override { return 0; }
+
     std::unique_ptr<Sock> Accept(sockaddr* addr, socklen_t* addr_len) const override
     {
         if (addr != nullptr) {

src/util/sock.cpp

@@ -74,6 +74,11 @@ int Sock::Connect(const sockaddr* addr, socklen_t addr_len) const
     return connect(m_socket, addr, addr_len);
 }
 
+int Sock::Bind(const sockaddr* addr, socklen_t addr_len) const
+{
+    return bind(m_socket, addr, addr_len);
+}
+
 std::unique_ptr<Sock> Sock::Accept(sockaddr* addr, socklen_t* addr_len) const
 {
 #ifdef WIN32

src/util/sock.h

@@ -97,6 +97,12 @@ public:
      */
     [[nodiscard]] virtual int Connect(const sockaddr* addr, socklen_t addr_len) const;
 
+    /**
+     * bind(2) wrapper. Equivalent to `bind(this->Get(), addr, addr_len)`. Code that uses this
+     * wrapper can be unit tested if this method is overridden by a mock Sock implementation.
+     */
+    [[nodiscard]] virtual int Bind(const sockaddr* addr, socklen_t addr_len) const;
+
     /**
      * accept(2) wrapper. Equivalent to `std::make_unique<Sock>(accept(this->Get(), addr, addr_len))`.
      * Code that uses this wrapper can be unit tested if this method is overridden by a mock Sock