phaneron/Kelsidavis-WoWee
1
0
Fork 0
mirror of https://github.com/Kelsidavis/WoWee.git synced 2026-04-05 04:33:51 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 2

fix: partial send on non-blocking socket silently dropped data

Browse source 
A single send() that returned fewer bytes than requested was logged but
not retried, leaving the server with a truncated packet. This causes an
irreversible TCP framing desync (next header lands mid-payload) that
manifests as a disconnect under network pressure. Added a retry loop
that handles EWOULDBLOCK with a brief yield.

Also rejects payloads > 64KB instead of silently truncating the 16-bit
CMSG size field, which would have written a wrong header while still
appending all bytes.
This commit is contained in:
Kelsi 2026-03-29 19:36:32 -07:00
parent e5b4e86600
commit 9da97e5e88
1 changed files with 30 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

37
src/network/world_socket.cpp
View file

@ -314,6 +314,14 @@ void WorldSocket::send(const Packet& packet) {
const auto& data = packet.getData();
uint16_t opcode = packet.getOpcode();
// CMSG header uses a 16-bit size field, so payloads > 64KB are unsupported.
// Guard here rather than silently truncating via cast, which would write a
// wrong size to the header while still appending all bytes.
if (data.size() > 0xFFFF) {
LOG_ERROR("Packet payload too large for CMSG header: ", data.size(),
" bytes (opcode=0x", std::hex, opcode, std::dec, "). Dropping.");
return;
}
uint16_t payloadLen = static_cast<uint16_t>(data.size());
// Debug: parse and log character-create payload fields (helps diagnose appearance issues).
@ -426,14 +434,29 @@ void WorldSocket::send(const Packet& packet) {
" payload=", payloadLen, " enc=", encryptionEnabled ? "yes" : "no");
}
// Send complete packet
ssize_t sent = net::portableSend(sockfd, sendData.data(), sendData.size());
if (sent < 0) {
LOG_ERROR("Send failed: ", net::errorString(net::lastError()));
} else {
if (static_cast<size_t>(sent) != sendData.size()) {
LOG_WARNING("Partial send: ", sent, " of ", sendData.size(), " bytes");
// Send complete packet, retrying on partial sends. Non-blocking sockets
// can return fewer bytes than requested when the kernel buffer is full.
// Without a retry loop, the server receives a truncated packet and the
// TCP stream permanently desyncs (next header lands mid-payload).
size_t totalSent = 0;
while (totalSent < sendData.size()) {
ssize_t sent = net::portableSend(sockfd, sendData.data() + totalSent,
sendData.size() - totalSent);
if (sent < 0) {
int err = net::lastError();
if (net::isWouldBlock(err)) {
// Kernel buffer full — yield briefly and retry.
std::this_thread::sleep_for(std::chrono::microseconds(100));
continue;
}
LOG_ERROR("Send failed: ", net::errorString(err));
break;
}
if (sent == 0) break; // connection closed
totalSent += static_cast<size_t>(sent);
}
if (totalSent != sendData.size()) {
LOG_WARNING("Incomplete send: ", totalSent, " of ", sendData.size(), " bytes");
}
}