Merge bitcoin/bitcoin#33378: Remove unnecessary casts when calling socket operations

67f632b net: remove unnecessary casts in socket operations (Matthew Zipkin)

Pull request description:

  During review of bitcoin/bitcoin#32747 several casting operations were questioned in existing code that had been copied or moved. That lead me to find a few other similar casts in the codebase.

  It turns out that since the `Sock` class wraps syscalls with its own internal casting (see bitcoin/bitcoin#24357 and bitcoin/bitcoin#20788 written in 2020-2022) we no longer need to cast the arguments when calling these functions. The original argument-casts are old and were cleaned up a bit in bitcoin/bitcoin#12855 written in 2018.

  The casting is only needed for windows compatibility, where those syscalls require a data argument to be of type `char*` specifically:

  https://learn.microsoft.com/en-us/windows/win32/api/winsock/nf-winsock-getsockopt

  ```
  int getsockopt(
    [in]      SOCKET s,
    [in]      int    level,
    [in]      int    optname,
    [out]     char   *optval,
    [in, out] int    *optlen
  );
  ```

  but on POSIX the argument is `void*`:

  https://www.man7.org/linux/man-pages/man2/getsockopt.2.html

  ```
         int getsockopt(socklen *restrict optlen;
                        int sockfd, int level, int optname,
                        void optval[_Nullable restrict *optlen],
                        socklen_t *restrict optlen);
  ```

ACKs for top commit:
  Raimo33:
    ACK 67f632b
  achow101:
    ACK 67f632b
  hodlinator:
    ACK 67f632b
  vasild:
    ACK 67f632b
  davidgumberg:
    ACK bitcoin/bitcoin@67f632b

Tree-SHA512: c326d7242698b8d4d019f630fb6281398da2773c4e5aad1e3bba093a012c2119ad8815f42bd009e61a9a90db9b8e6ed5c75174aac059c9df83dd3aa5618a9ba6

Author: achow101

src/compat/compat.h

@@ -75,14 +75,6 @@ typedef unsigned int SOCKET;
 typedef SSIZE_T ssize_t;
 #endif
 
-// The type of the option value passed to getsockopt & setsockopt
-// differs between Windows and non-Windows.
-#ifndef WIN32
-typedef void* sockopt_arg_type;
-#else
-typedef char* sockopt_arg_type;
-#endif
-
 #ifdef WIN32
 // Export main() and ensure working ASLR when using mingw-w64.
 // Exporting a symbol will prevent the linker from stripping

src/httpserver.cpp

@@ -401,7 +401,7 @@ static bool HTTPBindAddresses(struct evhttp* http)
             // Set the no-delay option (disable Nagle's algorithm) on the TCP socket.
             evutil_socket_t fd = evhttp_bound_socket_get_fd(bind_handle);
             int one = 1;
-            if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (sockopt_arg_type)&one, sizeof(one)) == SOCKET_ERROR) {
+            if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, reinterpret_cast<char*>(&one), sizeof(one)) == SOCKET_ERROR) {
                 LogInfo("WARNING: Unable to set TCP_NODELAY on RPC server socket, continuing anyway\n");
             }
             boundSockets.push_back(bind_handle);

src/net.cpp

@@ -1638,7 +1638,7 @@ std::pair<size_t, bool> CConnman::SocketSendData(CNode& node) const
                 flags |= MSG_MORE;
             }
 #endif
-            nBytes = node.m_sock->Send(reinterpret_cast<const char*>(data.data()), data.size(), flags);
+            nBytes = node.m_sock->Send(data.data(), data.size(), flags);
         }
         if (nBytes > 0) {
             node.m_last_send = GetTime<std::chrono::seconds>();
@@ -3139,7 +3139,7 @@ bool CConnman::BindListenPort(const CService& addrBind, bilingual_str& strError,
 
     // Allow binding if the port is still in TIME_WAIT state after
     // the program was closed and restarted.
-    if (sock->SetSockOpt(SOL_SOCKET, SO_REUSEADDR, (sockopt_arg_type)&nOne, sizeof(int)) == SOCKET_ERROR) {
+    if (sock->SetSockOpt(SOL_SOCKET, SO_REUSEADDR, &nOne, sizeof(int)) == SOCKET_ERROR) {
         strError = Untranslated(strprintf("Error setting SO_REUSEADDR on socket: %s, continuing anyway", NetworkErrorString(WSAGetLastError())));
         LogPrintf("%s\n", strError.original);
     }
@@ -3148,14 +3148,14 @@ bool CConnman::BindListenPort(const CService& addrBind, bilingual_str& strError,
     // and enable it by default or not. Try to enable it, if possible.
     if (addrBind.IsIPv6()) {
 #ifdef IPV6_V6ONLY
-        if (sock->SetSockOpt(IPPROTO_IPV6, IPV6_V6ONLY, (sockopt_arg_type)&nOne, sizeof(int)) == SOCKET_ERROR) {
+        if (sock->SetSockOpt(IPPROTO_IPV6, IPV6_V6ONLY, &nOne, sizeof(int)) == SOCKET_ERROR) {
             strError = Untranslated(strprintf("Error setting IPV6_V6ONLY on socket: %s, continuing anyway", NetworkErrorString(WSAGetLastError())));
             LogPrintf("%s\n", strError.original);
         }
 #endif
 #ifdef WIN32
         int nProtLevel = PROTECTION_LEVEL_UNRESTRICTED;
-        if (sock->SetSockOpt(IPPROTO_IPV6, IPV6_PROTECTION_LEVEL, (const char*)&nProtLevel, sizeof(int)) == SOCKET_ERROR) {
+        if (sock->SetSockOpt(IPPROTO_IPV6, IPV6_PROTECTION_LEVEL, &nProtLevel, sizeof(int)) == SOCKET_ERROR) {
             strError = Untranslated(strprintf("Error setting IPV6_PROTECTION_LEVEL on socket: %s, continuing anyway", NetworkErrorString(WSAGetLastError())));
             LogPrintf("%s\n", strError.original);
         }

src/netbase.cpp

@@ -551,7 +551,7 @@ std::unique_ptr<Sock> CreateSockOS(int domain, int type, int protocol)
     int set = 1;
     // Set the no-sigpipe option on the socket for BSD systems, other UNIXes
     // should use the MSG_NOSIGNAL flag for every send.
-    if (sock->SetSockOpt(SOL_SOCKET, SO_NOSIGPIPE, (void*)&set, sizeof(int)) == SOCKET_ERROR) {
+    if (sock->SetSockOpt(SOL_SOCKET, SO_NOSIGPIPE, &set, sizeof(int)) == SOCKET_ERROR) {
         LogPrintf("Error setting SO_NOSIGPIPE on socket: %s, continuing anyway\n",
                   NetworkErrorString(WSAGetLastError()));
     }
@@ -620,7 +620,7 @@ static bool ConnectToSocket(const Sock& sock, struct sockaddr* sockaddr, socklen
             // sockerr here.
             int sockerr;
             socklen_t sockerr_len = sizeof(sockerr);
-            if (sock.GetSockOpt(SOL_SOCKET, SO_ERROR, (sockopt_arg_type)&sockerr, &sockerr_len) ==
+            if (sock.GetSockOpt(SOL_SOCKET, SO_ERROR, &sockerr, &sockerr_len) ==
                 SOCKET_ERROR) {
                 LogPrintf("getsockopt() for %s failed: %s\n", dest_str, NetworkErrorString(WSAGetLastError()));
                 return false;

src/test/sock_tests.cpp

@@ -24,7 +24,7 @@ static bool SocketIsClosed(const SOCKET& s)
     // wrongly pretend that the socket is not closed.
     int type;
     socklen_t len = sizeof(type);
-    return getsockopt(s, SOL_SOCKET, SO_TYPE, (sockopt_arg_type)&type, &len) == SOCKET_ERROR;
+    return getsockopt(s, SOL_SOCKET, SO_TYPE, reinterpret_cast<char*>(&type), &len) == SOCKET_ERROR;
 }
 
 static SOCKET CreateSocket()