pppd: allow use of arbitrary interface names

This is a modified version of a patch from openSUSE that enables PPP interfaces
to be called arbitrary names, rather than simply pppX where X is the unit
number.

The modifications from the stock openSUSE patch are:
- refresh patch on top of 018_ip-up_option.diff
- fix a printf format-string vulnerability in pppd/main.c:set_ifunit()
- clarify the pppd.8 manpage additions
- patch pppstats/pppstats.c to query renamed interfaces without complaint

Origin: SUSE
Bug-Debian: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=458646
Forwarded: no
Reviewed-by: Chris Boot <bootc@debian.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

pppd/main.c

@@ -124,7 +124,7 @@
 static const char rcsid[] = RCSID;
 
 /* interface vars */
-char ifname[32];		/* Interface name */
+char ifname[MAXIFNAMELEN];	/* Interface name */
 int ifunit;			/* Interface unit number */
 
 struct channel *the_channel;
@@ -298,13 +298,6 @@ struct protent *protocols[] = {
     NULL
 };
 
-/*
- * If PPP_DRV_NAME is not defined, use the default "ppp" as the device name.
- */
-#if !defined(PPP_DRV_NAME)
-#define PPP_DRV_NAME	"ppp"
-#endif /* !defined(PPP_DRV_NAME) */
-
 int
 main(argc, argv)
     int argc;
@@ -737,8 +730,11 @@ void
 set_ifunit(iskey)
     int iskey;
 {
-    info("Using interface %s%d", PPP_DRV_NAME, ifunit);
-    slprintf(ifname, sizeof(ifname), "%s%d", PPP_DRV_NAME, ifunit);
+    if (req_ifname[0] != '\0')
+	slprintf(ifname, sizeof(ifname), "%s", req_ifname);
+    else
+	slprintf(ifname, sizeof(ifname), "%s%d", PPP_DRV_NAME, ifunit);
+    info("Using interface %s", ifname);
     script_setenv("IFNAME", ifname, iskey);
     if (iskey) {
 	create_pidfile(getpid());	/* write pid to file */

pppd/options.c

@@ -114,6 +114,7 @@ char	linkname[MAXPATHLEN];	/* logical name for link */
 bool	tune_kernel;		/* may alter kernel settings */
 int	connect_delay = 1000;	/* wait this many ms after connect script */
 int	req_unit = -1;		/* requested interface unit */
+char	req_ifname[MAXIFNAMELEN];	/* requested interface name */
 bool	multilink = 0;		/* Enable multilink operation */
 char	*bundle_name = NULL;	/* bundle name for multilink */
 bool	dump_options;		/* print out option values */
@@ -284,6 +285,10 @@ option_t general_options[] = {
       "PPP interface unit number to use if possible",
       OPT_PRIO | OPT_LLIMIT, 0, 0 },
 
+    { "ifname", o_string, req_ifname,
+      "Set PPP interface name",
+      OPT_PRIO | OPT_PRIV | OPT_STATIC, NULL, MAXIFNAMELEN },
+
     { "dump", o_bool, &dump_options,
       "Print out option values after parsing all options", 1 },
     { "dryrun", o_bool, &dryrun,

pppd/pppd.8

@@ -1079,7 +1079,13 @@ under Linux and FreeBSD 2.2.8 and later.
 .TP
 .B unit \fInum
 Sets the ppp unit number (for a ppp0 or ppp1 etc interface name) for outbound
-connections.
+connections.  If the unit is already in use a dynamically allocated number will
+be used.
+.TP
+.B ifname \fIstring
+Set the ppp interface name for outbound connections.  If the interface name is
+already in use, or if the name cannot be used for any other reason, pppd will
+terminate.
 .TP
 .B unset \fIname
 Remove a variable from the environment variable for scripts that are

pppd/pppd.h

@@ -80,6 +80,16 @@
 #define MAXARGS		1	/* max # args to a command */
 #define MAXNAMELEN	256	/* max length of hostname or name for auth */
 #define MAXSECRETLEN	256	/* max length of password or secret */
+#define MAXIFNAMELEN	32	/* max length of interface name; or use IFNAMSIZ, can we
+				   always include net/if.h? */
+
+/*
+ * If PPP_DRV_NAME is not defined, use the default "ppp" as the device name.
+ * Where should PPP_DRV_NAME come from? Do we include it here?
+ */
+#if !defined(PPP_DRV_NAME)
+#define PPP_DRV_NAME	"ppp"
+#endif /* !defined(PPP_DRV_NAME) */
 
 /*
  * Option descriptor structure.
@@ -318,6 +328,7 @@ extern bool	tune_kernel;	/* May alter kernel settings as necessary */
 extern int	connect_delay;	/* Time to delay after connect script */
 extern int	max_data_rate;	/* max bytes/sec through charshunt */
 extern int	req_unit;	/* interface unit number to use */
+extern char	req_ifname[MAXIFNAMELEN]; /* interface name to use */
 extern bool	multilink;	/* enable multilink operation */
 extern bool	noendpoint;	/* don't send or accept endpt. discrim. */
 extern char	*bundle_name;	/* bundle name for multilink */

pppd/sys-linux.c

@@ -643,6 +643,21 @@ static int make_ppp_unit()
 	}
 	if (x < 0)
 		error("Couldn't create new ppp unit: %m");
+
+	if (x == 0 && req_ifname[0] != '\0') {
+		struct ifreq ifr;
+		char t[MAXIFNAMELEN];
+		memset(&ifr, 0, sizeof(struct ifreq));
+		slprintf(t, sizeof(t), "%s%d", PPP_DRV_NAME, ifunit);
+		strncpy(ifr.ifr_name, t, IF_NAMESIZE);
+		strncpy(ifr.ifr_newname, req_ifname, IF_NAMESIZE);
+		x = ioctl(sock_fd, SIOCSIFNAME, &ifr);
+		if (x < 0)
+		    error("Couldn't rename interface %s to %s: %m", t, req_ifname);
+		else
+		    info("Renamed interface %s to %s", t, req_ifname);
+	}
+
 	return x;
 }
 

pppstats/pppstats.c

@@ -88,7 +88,6 @@ int	aflag;			/* print absolute values, not deltas */
 int	dflag;			/* print data rates, not bytes */
 int	interval, count;
 int	infinite;
-int	unit;
 int	s;			/* socket or /dev/ppp file descriptor */
 int	signalled;		/* set if alarm goes off "early" */
 char	*progname;
@@ -449,6 +448,7 @@ main(argc, argv)
 {
     int c;
 #ifdef STREAMS
+    int unit;
     char *dev;
 #endif
 
@@ -506,11 +506,6 @@ main(argc, argv)
     if (argc > 0)
 	interface = argv[0];
 
-    if (sscanf(interface, PPP_DRV_NAME "%d", &unit) != 1) {
-	fprintf(stderr, "%s: invalid interface '%s' specified\n",
-		progname, interface);
-    }
-
 #ifndef STREAMS
     {
 	struct ifreq ifr;
@@ -535,6 +530,11 @@ main(argc, argv)
     }
 
 #else	/* STREAMS */
+    if (sscanf(interface, PPP_DRV_NAME "%d", &unit) != 1) {
+	fprintf(stderr, "%s: invalid interface '%s' specified\n",
+		progname, interface);
+    }
+
 #ifdef __osf__
     dev = "/dev/streams/ppp";
 #else