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Don't limit channel window to 500MB #377

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Merged
merged 1 commit into from
Aug 29, 2025
Merged

Don't limit channel window to 500MB #377

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17 changes: 10 additions & 7 deletions src/common-channel.c
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Original file line number Diff line number Diff line change
Expand Up @@ -858,17 +858,21 @@ void common_recv_msg_channel_data(struct Channel *channel, int fd,
void recv_msg_channel_window_adjust() {

struct Channel * channel;
unsigned int incr;
unsigned int incr, newwin;

channel = getchannel();

incr = buf_getint(ses.payload);
TRACE(("received window increment %d", incr))
incr = MIN(incr, TRANS_MAX_WIN_INCR);
TRACE(("received window increment %u", incr))

channel->transwindow += incr;
channel->transwindow = MIN(channel->transwindow, TRANS_MAX_WINDOW);

newwin = channel->transwindow + incr;
if (newwin < channel->transwindow) {
/* Integer overflow, clamp it at maximum.
* Behaviour may be unexpected, senders MUST NOT overflow per rfc4254. */
TRACE(("overflow window, prev %u", channel->transwindow));
newwin = 0xffffffff;
}
channel->transwindow = newwin;
}

/* Increment the incoming data window for a channel, and let the remote
Expand Down Expand Up @@ -906,7 +910,6 @@ void recv_msg_channel_open() {

remotechan = buf_getint(ses.payload);
transwindow = buf_getint(ses.payload);
transwindow = MIN(transwindow, TRANS_MAX_WINDOW);
transmaxpacket = buf_getint(ses.payload);
transmaxpacket = MIN(transmaxpacket, TRANS_MAX_PAYLOAD_LEN);

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3 changes: 0 additions & 3 deletions src/sysoptions.h
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Expand Up @@ -243,9 +243,6 @@
#define RECV_MAX_PACKET_LEN (MAX(35000, ((RECV_MAX_PAYLOAD_LEN)+100)))

/* for channel code */
#define TRANS_MAX_WINDOW 500000000 /* 500MB is sufficient, stopping overflow */
#define TRANS_MAX_WIN_INCR 500000000 /* overflow prevention */

#define RECV_WINDOWEXTEND (opts.recv_window / 3) /* We send a "window extend" every
RECV_WINDOWEXTEND bytes */
#define MAX_RECV_WINDOW (10*1024*1024) /* 10 MB should be enough */
Expand Down