upstream: add a ssh_packet_process_read() function that reads from

a fd directly into the transport input buffer.

Use this in the client and server mainloops to avoid unnecessary
copying. It also lets us use a more greedy read size without penalty.

Yields a 2-3% performance gain on cipher-speed.sh (in a fairly
unscientific test tbf)

feedback dtucker@ ok markus@

OpenBSD-Commit-ID: df4112125bf79d8e38e79a77113e1b373078e632

1 files changed, 26 insertions, 1 deletions

diff --git a/packet.c b/packet.c
index 5a50fcd9..bde6c104 100644
--- a/packet.c
+++ b/packet.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: packet.c,v 1.306 2022/01/21 06:58:06 djm Exp $ */
+/* $OpenBSD: packet.c,v 1.307 2022/01/22 00:49:34 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1784,6 +1784,31 @@ ssh_packet_process_incoming(struct ssh *ssh, const char *buf, u_int len)
 	return 0;
 }
 
+/* Reads and buffers data from the specified fd */
+int
+ssh_packet_process_read(struct ssh *ssh, int fd)
+{
+	struct session_state *state = ssh->state;
+	int r;
+	size_t rlen;
+
+	if ((r = sshbuf_read(fd, state->input, PACKET_MAX_SIZE, &rlen)) != 0)
+		return r;
+
+	if (state->packet_discard) {
+		if ((r = sshbuf_consume_end(state->input, rlen)) != 0)
+			return r;
+		state->keep_alive_timeouts = 0; /* ?? */
+		if (rlen >= state->packet_discard) {
+			if ((r = ssh_packet_stop_discard(ssh)) != 0)
+				return r;
+		}
+		state->packet_discard -= rlen;
+		return 0;
+	}
+	return 0;
+}
+
 int
 ssh_packet_remaining(struct ssh *ssh)
 {