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Send packet uncompressed if zlib deflates to a larger size than input

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It's not guaranteed that deflate output will be smaller than the input.

In some cases zlib-ng (Z_BEST_SPEED) compression is causing packets to
increase in size and exceed m_max_packet_size. This results in the
packets never being fully received by the client.

Currently this is most reproducible in the spell_book section of the
OP_PlayerProfile message. After using #scribespells this portion of the
player profile has a lot of incrementing spellids which may be affecting
the compression algorithm. The client never processes the player profile
(MSG_SEND_PC) message and times out on zone entry.

This isn't necessarily a bug with zlib-ng since it inflates back to the
original input and normal zlib could do this too, but the current netcode
doesn't handle this.
This commit is contained in:
hg 2020-02-12 20:05:28 -05:00
parent 952fd43301
commit ed09d4ae54
1 changed files with 4 additions and 2 deletions
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6
common/net/daybreak_connection.cpp
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@ -1047,12 +1047,14 @@ void EQ::Net::DaybreakConnection::Compress(Packet &p, size_t offset, size_t leng
uint8_t new_buffer[2048] = { 0 };
uint8_t *buffer = (uint8_t*)p.Data() + offset;
uint32_t new_length = 0;
bool send_uncompressed = true;
if (length > 30) {
new_length = Deflate(buffer, (uint32_t)length, new_buffer + 1, 2048) + 1;
new_buffer[0] = 0x5a;
send_uncompressed = (new_length > length);
}
else {
if (send_uncompressed) {
memcpy(new_buffer + 1, buffer, length);
new_buffer[0] = 0xa5;
new_length = length + 1;
@ -1380,7 +1382,7 @@ void EQ::Net::DaybreakConnection::InternalQueuePacket(Packet &p, int stream_id,
}
auto stream = &m_streams[stream_id];
auto max_raw_size = m_max_packet_size - m_crc_bytes - DaybreakReliableHeader::size();
auto max_raw_size = m_max_packet_size - m_crc_bytes - DaybreakReliableHeader::size() - 1; // -1 for compress flag
size_t length = p.Length();
if (length > max_raw_size) {
DaybreakReliableFragmentHeader first_header;