diff options
Diffstat (limited to 'src/network/socket/qnativesocketengine_unix.cpp')
-rw-r--r-- | src/network/socket/qnativesocketengine_unix.cpp | 30 |
1 files changed, 25 insertions, 5 deletions
diff --git a/src/network/socket/qnativesocketengine_unix.cpp b/src/network/socket/qnativesocketengine_unix.cpp index a8f756dc31..bf94f6f606 100644 --- a/src/network/socket/qnativesocketengine_unix.cpp +++ b/src/network/socket/qnativesocketengine_unix.cpp @@ -868,22 +868,42 @@ qint64 QNativeSocketEnginePrivate::nativePendingDatagramSize() const if (recvResult != -1) recvResult = value; #else - QVarLengthArray<char, 8192> udpMessagePeekBuffer(8192); + // We need to grow the buffer to fit the entire datagram. + // We start at 1500 bytes (the MTU for Ethernet V2), which should catch + // almost all uses (effective MTU for UDP under IPv4 is 1468), except + // for localhost datagrams and those reassembled by the IP layer. + char udpMessagePeekBuffer[1500]; + struct msghdr msg; + struct iovec vec; + + memset(&msg, 0, sizeof(msg)); + msg.msg_iov = &vec; + msg.msg_iovlen = 1; + vec.iov_base = udpMessagePeekBuffer; + vec.iov_len = sizeof(udpMessagePeekBuffer); for (;;) { // the data written to udpMessagePeekBuffer is discarded, so // this function is still reentrant although it might not look // so. - recvResult = ::recv(socketDescriptor, udpMessagePeekBuffer.data(), - udpMessagePeekBuffer.size(), MSG_PEEK); + recvResult = ::recvmsg(socketDescriptor, &msg, MSG_PEEK); if (recvResult == -1 && errno == EINTR) continue; - if (recvResult != (ssize_t) udpMessagePeekBuffer.size()) + // was the result truncated? + if ((msg.msg_flags & MSG_TRUNC) == 0) break; - udpMessagePeekBuffer.resize(udpMessagePeekBuffer.size() * 2); + // grow by 16 times + msg.msg_iovlen *= 16; + if (msg.msg_iov != &vec) + delete[] msg.msg_iov; + msg.msg_iov = new struct iovec[msg.msg_iovlen]; + std::fill_n(msg.msg_iov, msg.msg_iovlen, vec); } + + if (msg.msg_iov != &vec) + delete[] msg.msg_iov; #endif #if defined (QNATIVESOCKETENGINE_DEBUG) |