--- ppp-2.4.4/pppd/demand.c
+++ ppp-2.4.4/pppd/demand.c
@@ -45,6 +45,7 @@
 #include <sys/socket.h>
 #ifdef PPP_FILTER
 #include <pcap-bpf.h>
+#include <linux/if_ether.h>
 #endif
 
 #include "pppd.h"
@@ -341,6 +342,7 @@
 	return 0;
     proto = PPP_PROTOCOL(p);
 #ifdef PPP_FILTER
+    *p = 1; /* set outbound for the filter rule */
     p[0] = 1;		/* outbound packet indicator */
     if ((pass_filter.bf_len != 0
 	 && bpf_filter(pass_filter.bf_insns, p, len, len) == 0)
@@ -350,6 +352,7 @@
 	return 0;
     }
     p[0] = 0xff;
+    *p = 0xff; /* restore original ppp header */
 #endif
     for (i = 0; (protp = protocols[i]) != NULL; ++i) {
 	if (protp->protocol < 0xC000 && (protp->protocol & ~0x8000) == proto) {
--- ppp-2.4.4/pppd/options.c
+++ ppp-2.4.4/pppd/options.c
@@ -1459,6 +1459,10 @@
     int ret = 1;
 
     pc = pcap_open_dead(DLT_PPP_PPPD, 65535);
+    if (!pc) {
+        option_error("error in pass-filter expression: pcap_open_dead failed\n");
+        return 0;
+    }
     if (pcap_compile(pc, &pass_filter, *argv, 1, netmask) == -1) {
 	option_error("error in pass-filter expression: %s\n",
 		     pcap_geterr(pc));
@@ -1480,6 +1484,11 @@
     int ret = 1;
 
     pc = pcap_open_dead(DLT_PPP_PPPD, 65535);
+    if (!pc) {
+        option_error("error in active-filter expression: pcap_open_dead failed\n");
+        return 0;
+    }
+
     if (pcap_compile(pc, &active_filter, *argv, 1, netmask) == -1) {
 	option_error("error in active-filter expression: %s\n",
 		     pcap_geterr(pc));