Patch submitted by Delman Lee <delman@mipgsun.mipg.upenn.edu>

This is a patch allows PPP to work with tcpdump 3.0
-Adam (acaldwel@103mort2.cs.ohiou.edu)

--- libpcap-0.0/pcap-linux.c.orig	Wed Aug  3 15:17:22 1994
+++ libpcap-0.0/pcap-linux.c	Wed Aug  3 16:04:02 1994
@@ -61,6 +61,10 @@
     buf = (char *)p->buffer+16;
     bufsize = p->bufsize - 16;
     memset(p->buffer,0,16);
+  } else if (p->linktype == DLT_PPP) {
+    buf = (char *)p->buffer+4;
+    bufsize = p->bufsize - 4;
+    memset(p->buffer,0,4);
   } else {
     buf = (char *)p->buffer;
     bufsize = p->bufsize;
@@ -82,6 +86,8 @@
 
   if (p->linktype == DLT_SLIP)
     datalen+=16;
+  else if (p->linktype == DLT_PPP)
+    datalen+=4;
 
   caplen = (datalen > p->bufsize) ? datalen : p->bufsize;
 
@@ -130,6 +136,8 @@
     p->linktype = DLT_EN10MB;
   else if (strncmp("sl", device, 2) == 0)
     p->linktype = DLT_SLIP;
+  else if (strncmp("pp", device, 2) == 0)
+    p->linktype = DLT_PPP;
   else {
     sprintf(ebuf, "snoop: unknown physical layer type");
     goto bad;
@@ -147,7 +155,7 @@
     goto bad;
   }
 
-  if (p->linktype != DLT_SLIP && promisc) {
+  if (p->linktype != DLT_SLIP && p->linktype != DLT_PPP && promisc) {
     strcpy(ifr.ifr_name, device);       /* interface we're gonna use */
     if (ioctl(p->fd, SIOCGIFFLAGS, &ifr) < 0 ) {    /* get flags */
       sprintf(ebuf, "socket ioctl get: %s", pcap_strerror(errno));