Merge bitcoin/bitcoin#25426: net: add new method Sock::GetSockName() that wraps getsockname() and use it in GetBindAddress()

a8d6abba5e net: change GetBindAddress() to take Sock argument (Vasil Dimov)
748dbcd9f2 net: add new method Sock::GetSockName() that wraps getsockname() (Vasil Dimov)

Pull request description:

  _This is a piece of #21878, chopped off to ease review._

  Wrap the syscall `getsockname()` in `Sock::GetSockName()` and change `GetBindAddress()` to take a `Sock` argument so that it can use the wrapper.

  This further encapsulates syscalls inside the `Sock` class and makes the callers mockable.

ACKs for top commit:
  laanwj:
    Code review ACK a8d6abba5e

Tree-SHA512: 3a73463258c0057487fb3fd67215816b03a1c5160f45e45930eaeef86bb3611ec385794cdb08339aa074feba8ad67cd2bfd3836f6cbd40834e15d933214a05dc

src/net.cpp

@@ -422,13 +422,13 @@ bool CConnman::CheckIncomingNonce(uint64_t nonce)
 }
 
 /** Get the bind address for a socket as CAddress */
-static CAddress GetBindAddress(SOCKET sock)
+static CAddress GetBindAddress(const Sock& sock)
 {
     CAddress addr_bind;
     struct sockaddr_storage sockaddr_bind;
     socklen_t sockaddr_bind_len = sizeof(sockaddr_bind);
-    if (sock != INVALID_SOCKET) {
-        if (!getsockname(sock, (struct sockaddr*)&sockaddr_bind, &sockaddr_bind_len)) {
+    if (sock.Get() != INVALID_SOCKET) {
+        if (!sock.GetSockName((struct sockaddr*)&sockaddr_bind, &sockaddr_bind_len)) {
             addr_bind.SetSockAddr((const struct sockaddr*)&sockaddr_bind);
         } else {
             LogPrintLevel(BCLog::NET, BCLog::Level::Warning, "getsockname failed\n");
@@ -540,7 +540,7 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
     NodeId id = GetNewNodeId();
     uint64_t nonce = GetDeterministicRandomizer(RANDOMIZER_ID_LOCALHOSTNONCE).Write(id).Finalize();
     if (!addr_bind.IsValid()) {
-        addr_bind = GetBindAddress(sock->Get());
+        addr_bind = GetBindAddress(*sock);
     }
     CNode* pnode = new CNode(id,
                              nLocalServices,
@@ -1154,7 +1154,7 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
         addr = CAddress{MaybeFlipIPv6toCJDNS(addr), NODE_NONE};
     }
 
-    const CAddress addr_bind{MaybeFlipIPv6toCJDNS(GetBindAddress(sock->Get())), NODE_NONE};
+    const CAddress addr_bind{MaybeFlipIPv6toCJDNS(GetBindAddress(*sock)), NODE_NONE};
 
     NetPermissionFlags permissionFlags = NetPermissionFlags::None;
     hListenSocket.AddSocketPermissionFlags(permissionFlags);

src/test/fuzz/util.cpp

@@ -201,6 +201,20 @@ int FuzzedSock::SetSockOpt(int, int, const void*, socklen_t) const
     return 0;
 }
 
+int FuzzedSock::GetSockName(sockaddr* name, socklen_t* name_len) const
+{
+    constexpr std::array getsockname_errnos{
+        ECONNRESET,
+        ENOBUFS,
+    };
+    if (m_fuzzed_data_provider.ConsumeBool()) {
+        SetFuzzedErrNo(m_fuzzed_data_provider, getsockname_errnos);
+        return -1;
+    }
+    *name_len = m_fuzzed_data_provider.ConsumeData(name, *name_len);
+    return 0;
+}
+
 bool FuzzedSock::Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred) const
 {
     constexpr std::array wait_errnos{

src/test/fuzz/util.h

@@ -67,6 +67,8 @@ public:
 
     int SetSockOpt(int level, int opt_name, const void* opt_val, socklen_t opt_len) const override;
 
+    int GetSockName(sockaddr* name, socklen_t* name_len) const override;
+
     bool Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred = nullptr) const override;
 
     bool WaitMany(std::chrono::milliseconds timeout, EventsPerSock& events_per_sock) const override;

src/test/util/net.h

@@ -147,6 +147,12 @@ public:
 
     int SetSockOpt(int, int, const void*, socklen_t) const override { return 0; }
 
+    int GetSockName(sockaddr* name, socklen_t* name_len) const override
+    {
+        std::memset(name, 0x0, *name_len);
+        return 0;
+    }
+
     bool Wait(std::chrono::milliseconds timeout,
               Event requested,
               Event* occurred = nullptr) const override

src/util/sock.cpp

@@ -102,6 +102,11 @@ int Sock::SetSockOpt(int level, int opt_name, const void* opt_val, socklen_t opt
     return setsockopt(m_socket, level, opt_name, static_cast<const char*>(opt_val), opt_len);
 }
 
+int Sock::GetSockName(sockaddr* name, socklen_t* name_len) const
+{
+    return getsockname(m_socket, name, name_len);
+}
+
 bool Sock::Wait(std::chrono::milliseconds timeout, Event requested, Event* occurred) const
 {
     // We need a `shared_ptr` owning `this` for `WaitMany()`, but don't want

src/util/sock.h

@@ -114,6 +114,13 @@ public:
                                          const void* opt_val,
                                          socklen_t opt_len) const;
 
+    /**
+     * getsockname(2) wrapper. Equivalent to
+     * `getsockname(this->Get(), name, name_len)`. Code that uses this
+     * wrapper can be unit tested if this method is overridden by a mock Sock implementation.
+     */
+    [[nodiscard]] virtual int GetSockName(sockaddr* name, socklen_t* name_len) const;
+
     using Event = uint8_t;
 
     /**