Merge bitcoin/bitcoin#28649: Do the SOCKS5 handshake reliably

af0fca530e4d8311bcb24a14c416e5ad7c30ff78 netbase: use reliable send() during SOCKS5 handshake (Vasil Dimov)
1b19d1117ca5373a15313227b547ef4392022dbd sock: change Sock::SendComplete() to take Span (Vasil Dimov)

Pull request description:

  The `Socks5()` function which does the SOCKS5 handshake with the SOCKS5 proxy sends bytes to the socket without retrying partial writes.

  `send(2)` may write only part of the provided data and return. In this case the caller is responsible for retrying the operation with the remaining data. Change `Socks5()` to do that. There is already a method `Sock::SendComplete()` which does exactly that, so use it in `Socks5()`.

  A minor complication for this PR is that `Sock::SendComplete()` takes `std::string` argument whereas `Socks5()` has `std::vector<uint8_t>`. Thus the necessity for the first commit. It is possible to do also in other ways - convert the data in `Socks5()` to `std::string` or have just one `Sock::SendComplete()` that takes `void*` and change the callers to pass `str.data(), str.size()` or `vec.data(), vec.size()`.

  This came up while testing https://github.com/bitcoin/bitcoin/pull/27375.

ACKs for top commit:
  achow101:
    ACK af0fca530e4d8311bcb24a14c416e5ad7c30ff78
  jonatack:
    ACK af0fca530e4d8311bcb24a14c416e5ad7c30ff78
  pinheadmz:
    ACK af0fca530e4d8311bcb24a14c416e5ad7c30ff78

Tree-SHA512: 1d4a53d0628f7607378038ac56dc3b8624ce9322b034c9547a0c3ce052eafb4b18213f258aa3b57bcb4d990a5e0548a37ec70af2bd55f6e8e6399936f1ce047a

2 files changed, 16 insertions, 2 deletions

diff --git a/src/util/sock.cpp b/src/util/sock.cpp
index d16dc56aa3..e896b87160 100644
--- a/src/util/sock.cpp
+++ b/src/util/sock.cpp
@@ -242,7 +242,7 @@ bool Sock::WaitMany(std::chrono::milliseconds timeout, EventsPerSock& events_per
 #endif /* USE_POLL */
 }
 
-void Sock::SendComplete(const std::string& data,
+void Sock::SendComplete(Span<const unsigned char> data,
                         std::chrono::milliseconds timeout,
                         CThreadInterrupt& interrupt) const
 {
@@ -283,6 +283,13 @@ void Sock::SendComplete(const std::string& data,
     }
 }
 
+void Sock::SendComplete(Span<const char> data,
+                        std::chrono::milliseconds timeout,
+                        CThreadInterrupt& interrupt) const
+{
+    SendComplete(MakeUCharSpan(data), timeout, interrupt);
+}
+
 std::string Sock::RecvUntilTerminator(uint8_t terminator,
                                       std::chrono::milliseconds timeout,
                                       CThreadInterrupt& interrupt,
diff --git a/src/util/sock.h b/src/util/sock.h
index d78e01929b..65e7ffc165 100644
--- a/src/util/sock.h
+++ b/src/util/sock.h
@@ -228,7 +228,14 @@ public:
      * @throws std::runtime_error if the operation cannot be completed. In this case only some of
      * the data will be written to the socket.
      */
-    virtual void SendComplete(const std::string& data,
+    virtual void SendComplete(Span<const unsigned char> data,
+                              std::chrono::milliseconds timeout,
+                              CThreadInterrupt& interrupt) const;
+
+    /**
+     * Convenience method, equivalent to `SendComplete(MakeUCharSpan(data), timeout, interrupt)`.
+     */
+    virtual void SendComplete(Span<const char> data,
                               std::chrono::milliseconds timeout,
                               CThreadInterrupt& interrupt) const;