pppoe-discovery: Do not set eth0 as default interface

On most Linux systems there is no network interface with name eth0.

So rather make -I interface option as mandatory and do not rely on some
default hardcoded interface name.

Signed-off-by: Pali Rohár <pali@kernel.org>

2 files changed, 6 insertions, 5 deletions

diff --git a/pppd/plugins/pppoe/pppoe-discovery.8 b/pppd/plugins/pppoe/pppoe-discovery.8
index d0a93db..e048f66 100644
--- a/pppd/plugins/pppoe/pppoe-discovery.8
+++ b/pppd/plugins/pppoe/pppoe-discovery.8
@@ -26,7 +26,7 @@ Under Linux, it is typically eth0 or eth1.
 The interface should be \(lqup\(rq before you start
 \fBpppoe\-discovery\fR, but should \fInot\fR be configured to have an
 IP address.
-The default interface is eth0.
+This option is mandatory.
 .RE
 .TP
 .BI \-D " file_name"
diff --git a/pppd/plugins/pppoe/pppoe-discovery.c b/pppd/plugins/pppoe/pppoe-discovery.c
index 1fe999d..4ac5106 100644
--- a/pppd/plugins/pppoe/pppoe-discovery.c
+++ b/pppd/plugins/pppoe/pppoe-discovery.c
@@ -251,9 +251,10 @@ int main(int argc, char *argv[])
 	}
     }
 
-    /* default interface name */
-    if (!conn->ifName)
-	conn->ifName = xstrdup("eth0");
+    if (!conn->ifName) {
+	fprintf(stderr, "Interface was not specified\n");
+	exit(EXIT_FAILURE);
+    }
 
     conn->sessionSocket = -1;
 
@@ -276,7 +277,7 @@ usage(void)
 {
     fprintf(stderr, "Usage: pppoe-discovery [options]\n");
     fprintf(stderr, "Options:\n");
-    fprintf(stderr, "   -I if_name     -- Specify interface (default eth0)\n");
+    fprintf(stderr, "   -I if_name     -- Specify interface (mandatory option)\n");
     fprintf(stderr, "   -D filename    -- Log debugging information in filename.\n");
     fprintf(stderr,
 	    "   -t timeout     -- Initial timeout for discovery packets in seconds\n"