From 7fd81113e6cca7360dbec0dafcf694c11bca03f6 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Tue, 25 Apr 2023 19:23:52 +0200
Subject: [PATCH] Warn about tunnel buffer being full only once per second

Otherwise, when the network output bandwidth is full, we additionally
fill the disk with logs.
---
 l2tpns.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/l2tpns.c b/l2tpns.c
index 3d722e5..0caf17b 100644
--- a/l2tpns.c
+++ b/l2tpns.c
@@ -1301,7 +1301,20 @@ void tunnelsend(uint8_t * buf, uint16_t l, tunnelidt t)
 
 	if (sendto(udpfd[tunnel[t].indexudp], buf, l, 0, (void *) &addr, sizeof(addr)) < 0)
 	{
-		LOG(0, ntohs((*(uint16_t *) (buf + 6))), t, "Error sending data out tunnel: %s (udpfd=%d, buf=%p, len=%d, dest=%s)\n",
+		sessionidt s = ntohs((*(uint16_t *) (buf + 6)));
+		if (errno == EAGAIN)
+		{
+			static time_t lastwarn;
+			time_t newtime = time(NULL);
+
+			if (lastwarn != newtime)
+			{
+				lastwarn = newtime;
+				LOG(0, 0, t, "Error sending data out tunnel: buffer full\n");
+			}
+		}
+		else
+			LOG(0, s, t, "Error sending data out tunnel: %s (udpfd=%d, buf=%p, len=%d, dest=%s)\n",
 				strerror(errno), udpfd[tunnel[t].indexudp], buf, l, inet_ntoa(addr.sin_addr));
 		STAT(tunnel_tx_errors);
 		return;