To double the receive buffer of a socketpair does not help as sending

checks the send buffer size.  So double both buffer sizes.
Moreover the default for sending is 2048 and for receiving is 4096.
This makes the existing double buffer algorithm inconsistent.  It
is better to make the buffers large enough to hold 8 full length
messages.  Just make sure that it does not shrink.
Keep the approach that doubles the buffer sizes.  When we are low
on buffers and cannot reach the full size, increase it as much as
possible.
While there, add consistent error messages.
OK benno@

1 files changed, 25 insertions, 14 deletions

diff --git a/usr.sbin/syslogd/syslogd.c b/usr.sbin/syslogd/syslogd.c
index 1ce43911e4b..4c1e68e0c12 100644
--- a/usr.sbin/syslogd/syslogd.c
+++ b/usr.sbin/syslogd/syslogd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: syslogd.c,v 1.183 2015/09/03 20:50:48 bluhm Exp $	*/
+/*	$OpenBSD: syslogd.c,v 1.184 2015/09/09 08:12:46 bluhm Exp $	*/
 
 /*
  * Copyright (c) 1983, 1988, 1993, 1994
@@ -337,7 +337,7 @@ int	getmsgbufsize(void);
 int	socket_bind(const char *, const char *, const char *, int,
     int *, int *);
 int	unix_socket(char *, int, mode_t);
-void	double_rbuf(int);
+void	double_sockbuf(int, int);
 void	tailify_replytext(char *, int);
 
 int
@@ -484,13 +484,16 @@ main(int argc, char *argv[])
 				die(0);
 			continue;
 		}
-		double_rbuf(fd_unix[i]);
+		double_sockbuf(fd_unix[i], SO_RCVBUF);
 	}
 
-	if (socketpair(AF_UNIX, SOCK_DGRAM, PF_UNSPEC, pair) == -1)
+	if (socketpair(AF_UNIX, SOCK_DGRAM, PF_UNSPEC, pair) == -1) {
+		logerror("socketpair");
 		die(0);
+	}
+	double_sockbuf(pair[0], SO_RCVBUF);
+	double_sockbuf(pair[1], SO_SNDBUF);
 	fd_sendsys = pair[0];
-	double_rbuf(fd_sendsys);
 
 	fd_ctlsock = fd_ctlconn = -1;
 	if (path_ctlsock != NULL) {
@@ -792,7 +795,7 @@ socket_bind(const char *proto, const char *host, const char *port,
 			continue;
 		}
 		if (!shutread && res->ai_protocol == IPPROTO_UDP)
-			double_rbuf(*fdp);
+			double_sockbuf(*fdp, SO_RCVBUF);
 	}
 
 	freeaddrinfo(res0);
@@ -2671,20 +2674,28 @@ unix_socket(char *path, int type, mode_t mode)
 	optval = MAXLINE + PATH_MAX;
 	if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &optval, sizeof(optval))
 	    == -1)
-		logerror("cannot setsockopt unix");
+		logerror("setsockopt unix");
 
 	return (fd);
 }
 
 void
-double_rbuf(int fd)
+double_sockbuf(int fd, int optname)
 {
-	socklen_t slen, len;
-
-	slen = sizeof(len);
-	if (getsockopt(fd, SOL_SOCKET, SO_RCVBUF, &len, &slen) == 0) {
-		len *= 2;
-		setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &len, slen);
+	socklen_t len;
+	int i, newsize, oldsize = 0;
+
+	len = sizeof(oldsize);
+	if (getsockopt(fd, SOL_SOCKET, optname, &oldsize, &len) == -1)
+		logerror("getsockopt bufsize");
+	len = sizeof(newsize);
+	newsize =  MAXLINE + 128;  /* data + control */
+	/* allow 8 full length messages */
+	for (i = 0; i < 4; i++, newsize *= 2) {
+		if (newsize <= oldsize)
+			continue;
+		if (setsockopt(fd, SOL_SOCKET, optname, &newsize, len) == -1)
+			logerror("setsockopt bufsize");
 	}
 }