syslogd: Increase message size limits

Add a -M option to control the maximum length of forwarded messages.
syslogd(8) used to truncate forwarded messages to 1024 bytes, but after
commit 1a874a1 ("Add RFC 5424 syslog message output to syslogd.")
applies a more conservative limit of 480 bytes for IPv4 per RFC 5426
section 3.2.  Restore the old default behaviour of truncating to 1024
bytes.  RFC 5424 specifies no upper limit on the length of forwarded
messages, while for RFC 3164 the limit is 1024 bytes.

Increase MAXLINE to 8192 bytes to correspond to commit 672ef817a192.

Replaced bootfile[] size for MAXPATHLEN used in getbootfile(3) as a
returned value. Using (MAXLINE+1) as a size for bootfile[] is excessive.

PR:		241937
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D27206

usr.sbin/syslogd/syslogd.8

@@ -41,6 +41,7 @@
 .Op Fl b Ar bind_address
 .Op Fl f Ar config_file
 .Op Fl l Oo Ar mode Ns \&: Oc Ns Ar path
+.Op Fl M Ar fwd_length
 .Op Fl m Ar mark_interval
 .Op Fl O Ar format
 .Op Fl P Ar pid_file
@@ -243,6 +244,11 @@ Usually the
 .Dq kern
 facility is reserved for messages read directly from
 .Pa /dev/klog .
+.It Fl M Ar fwd_length
+Set the limit on the length of forwarded messages.
+The minimum is 480 octets.
+The maximum for RFC 3164 output format is 1024 octets.
+The default is 1024 octets.
 .It Fl m Ar mark_interval
 Select the number of minutes between
 .Dq mark

usr.sbin/syslogd/syslogd.c

@@ -97,8 +97,7 @@ __FBSDID("$FreeBSD$");
  * Priority comparison code by Harlan Stenn.
  */
 
-/* Maximum number of characters in time of last occurrence */
-#define	MAXLINE		2048		/* maximum line length */
+#define	MAXLINE		8192		/* maximum line length */
 #define	MAXSVLINE	MAXLINE		/* maximum saved line length */
 #define	DEFUPRI		(LOG_USER|LOG_NOTICE)
 #define	DEFSPRI		(LOG_KERN|LOG_CRIT)
@@ -383,6 +382,7 @@ static int	MarkInterval = 20 * 60;	/* interval between marks in seconds */
 static int	MarkSeq;	/* mark sequence number */
 static int	NoBind;		/* don't bind() as suggested by RFC 3164 */
 static int	SecureMode;	/* when true, receive only unix domain socks */
+static int	MaxForwardLen = 1024;	/* max length of forwared message */
 #ifdef INET6
 static int	family = PF_UNSPEC; /* protocol family (IPv4, IPv6 or both) */
 #else
@@ -394,7 +394,7 @@ static int	use_bootfile;	/* log entire bootfile for every kern msg */
 static int	no_compress;	/* don't compress messages (1=pipes, 2=all) */
 static int	logflags = O_WRONLY|O_APPEND; /* flags used to open log files */
 
-static char	bootfile[MAXLINE+1]; /* booted kernel file */
+static char	bootfile[MAXPATHLEN]; /* booted kernel file */
 
 static int	RemoteAddDate;	/* Always set the date on remote messages */
 static int	RemoteHostname;	/* Log remote hostname from the message */
@@ -553,7 +553,7 @@ main(int argc, char *argv[])
 	if (madvise(NULL, 0, MADV_PROTECT) != 0)
 		dprintf("madvise() failed: %s\n", strerror(errno));
 
-	while ((ch = getopt(argc, argv, "468Aa:b:cCdf:FHkl:m:nNoO:p:P:sS:Tuv"))
+	while ((ch = getopt(argc, argv, "468Aa:b:cCdf:FHkl:M:m:nNoO:p:P:sS:Tuv"))
 	    != -1)
 		switch (ch) {
 #ifdef INET
@@ -666,6 +666,12 @@ main(int argc, char *argv[])
 			});
 			break;
 		   }
+		case 'M':		/* max length of forwarded message */
+			MaxForwardLen = atoi(optarg);
+			if (MaxForwardLen < 480)
+				errx(1, "minimum length limit of forwarded "
+				        "messages is 480 bytes");
+			break;
 		case 'm':		/* mark interval */
 			MarkInterval = atoi(optarg) * 60;
 			break;
@@ -710,6 +716,9 @@ main(int argc, char *argv[])
 	if ((argc -= optind) != 0)
 		usage();
 
+	if (RFC3164OutputFormat && MaxForwardLen > 1024)
+		errx(1, "RFC 3164 messages may not exceed 1024 bytes");
+
 	/* Pipe to catch a signal during select(). */
 	s = pipe2(sigpipe, O_CLOEXEC);
 	if (s < 0) {
@@ -948,9 +957,9 @@ usage(void)
 	fprintf(stderr,
 		"usage: syslogd [-468ACcdFHknosTuv] [-a allowed_peer]\n"
 		"               [-b bind_address] [-f config_file]\n"
-		"               [-l [mode:]path] [-m mark_interval]\n"
-		"               [-O format] [-P pid_file] [-p log_socket]\n"
-		"               [-S logpriv_socket]\n");
+		"               [-l [mode:]path] [-M fwd_length]\n"
+		"               [-m mark_interval] [-O format] [-P pid_file]\n"
+		"               [-p log_socket] [-S logpriv_socket]\n");
 	exit(1);
 }
 
@@ -1840,27 +1849,27 @@ fprintlog_write(struct filed *f, struct iovlist *il, int flags)
 
 	switch (f->f_type) {
 	case F_FORW:
-		/* Truncate messages to RFC 5426 recommended size. */
 		dprintf(" %s", f->fu_forw_hname);
 		switch (f->fu_forw_addr->ai_family) {
 #ifdef INET
 		case AF_INET:
 			dprintf(":%d\n",
 			    ntohs(satosin(f->fu_forw_addr->ai_addr)->sin_port));
-			iovlist_truncate(il, 480);
 			break;
 #endif
 #ifdef INET6
 		case AF_INET6:
 			dprintf(":%d\n",
 			    ntohs(satosin6(f->fu_forw_addr->ai_addr)->sin6_port));
-			iovlist_truncate(il, 1180);
 			break;
 #endif
 		default:
 			dprintf("\n");
 		}
 
+		/* Truncate messages to maximum forward length. */
+		iovlist_truncate(il, MaxForwardLen);
+
 		lsent = 0;
 		for (r = f->fu_forw_addr; r; r = r->ai_next) {
 			memset(&msghdr, 0, sizeof(msghdr));
@@ -2553,7 +2562,7 @@ init(int signo)
 	char *p;
 	char oldLocalHostName[MAXHOSTNAMELEN];
 	char hostMsg[2*MAXHOSTNAMELEN+40];
-	char bootfileMsg[LINE_MAX];
+	char bootfileMsg[MAXLINE + 1];
 
 	dprintf("init\n");
 	WantInitialize = 0;
@@ -2900,7 +2909,7 @@ cfline(const char *line, const char *prog, const char *host,
 	int error, i, pri, syncfile;
 	const char *p, *q;
 	char *bp, *pfilter_dup;
-	char buf[MAXLINE], ebuf[100];
+	char buf[LINE_MAX], ebuf[100];
 
 	dprintf("cfline(\"%s\", f, \"%s\", \"%s\", \"%s\")\n", line, prog,
 	    host, pfilter);