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Workaround for bug in some TCP implementations

This commit is contained in:
M66B 2018-04-27 08:38:15 +02:00
parent 9752cfdd99
commit 2d7e4781d4
2 changed files with 7 additions and 1 deletions
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1
app/src/main/jni/netguard/netguard.h
View File

@ -160,6 +160,7 @@ struct tcp_session {
uint8_t send_scale;
uint32_t recv_window; // host notation, scaled
uint32_t send_window; // host notation, scaled
uint16_t unconfirmed; // packets
uint32_t remote_seq; // confirmed bytes received, host notation
uint32_t local_seq; // confirmed bytes sent, host notation

7
app/src/main/jni/netguard/tcp.c
View File

@ -172,6 +172,7 @@ uint32_t get_send_window(const struct tcp_session *cur) {
behind = (cur->local_seq - cur->acked);
else
behind = (0x10000 + cur->local_seq - cur->acked);
behind += (cur->unconfirmed + 1) * 40; // Maximum header size
uint32_t window = (behind < cur->send_window ? cur->send_window - behind : 0);
return window;
@ -584,8 +585,10 @@ void check_tcp_socket(const struct arguments *args,
s->tcp.received += bytes;
// Forward to tun
if (write_data(args, &s->tcp, buffer, (size_t) bytes) >= 0)
if (write_data(args, &s->tcp, buffer, (size_t) bytes) >= 0) {
s->tcp.local_seq += bytes;
s->tcp.unconfirmed++;
}
}
free(buffer);
}
@ -711,6 +714,7 @@ jboolean handle_tcp(const struct arguments *args,
s->tcp.recv_scale = ws;
s->tcp.send_scale = ws;
s->tcp.send_window = ((uint32_t) ntohs(tcphdr->window)) << s->tcp.send_scale;
s->tcp.unconfirmed = 0;
s->tcp.remote_seq = ntohl(tcphdr->seq); // ISN remote
s->tcp.local_seq = (uint32_t) rand(); // ISN local
s->tcp.remote_start = s->tcp.remote_seq;
@ -823,6 +827,7 @@ jboolean handle_tcp(const struct arguments *args,
if (!tcphdr->syn)
cur->tcp.time = time(NULL);
cur->tcp.send_window = ((uint32_t) ntohs(tcphdr->window)) << cur->tcp.send_scale;
cur->tcp.unconfirmed = 0;
// Do not change the order of the conditions