Fix up error message printing. Base UDP checksum on UDP header length.

1 files changed, 48 insertions, 16 deletions

diff --git a/common/packet.c b/common/packet.c
index 66a13712..f354100e 100644
--- a/common/packet.c
+++ b/common/packet.c
@@ -22,7 +22,7 @@
 
 #ifndef lint
 static char copyright[] =
-"$Id: packet.c,v 1.23 1999/03/26 19:19:44 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium.  All rights reserved.\n";
+"$Id: packet.c,v 1.24 1999/04/12 21:37:03 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium.  All rights reserved.\n";
 #endif /* not lint */
 
 #include "dhcpd.h"
@@ -217,18 +217,25 @@ ssize_t decode_hw_header (interface, buf, bufix, from)
 
 /* UDP header and IP header decoded together for convenience. */
 
-ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
+ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, buflen)
 	struct interface_info *interface;
 	unsigned char *buf;
 	int bufix;
 	struct sockaddr_in *from;
 	unsigned char *data;
-	int len;
+	int buflen;
 {
   struct ip *ip;
   struct udphdr *udp;
   u_int32_t ip_len = (buf [bufix] & 0xf) << 2;
   u_int32_t sum, usum;
+  static int ip_packets_seen;
+  static int ip_packets_bad_checksum;
+  static int udp_packets_seen;
+  static int udp_packets_bad_checksum;
+  static int udp_packets_length_checked;
+  static int udp_packets_length_overflow;
+  int len;
 
   ip = (struct ip *)(buf + bufix);
   udp = (struct udphdr *)(buf + bufix + ip_len);
@@ -243,18 +250,24 @@ ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
 	  return -1;
 #endif /* USERLAND_FILTER */
 
+  ++ip_packets_seen;
   /* Check the IP header checksum - it should be zero. */
   if (wrapsum (checksum (buf + bufix, ip_len, 0))) {
-	  static int packets_seen;
-	  static int packets_bad_checksum;
-
-	  if (packets_seen &&
-	      (++packets_seen / ++packets_bad_checksum) < 2)
-		  log_info ("Bad IP checksum: %x",
-			    wrapsum (checksum (buf + bufix, sizeof *ip, 0)));
+	  ++ip_packets_bad_checksum;
+	  if (ip_packets_seen > 4 &&
+	      (++ip_packets_seen / ++ip_packets_bad_checksum) < 2) {
+		  log_info ("%d bad IP checksums seen in %d packets",
+			    ip_packets_bad_checksum, ip_packets_seen);
+		  ip_packets_seen = ip_packets_bad_checksum = 0;
+	  }
 	  return -1;
   }
 
+  /* Check the IP packet length. */
+  if (ntohs (ip -> ip_len) != buflen)
+	  log_debug ("ip length %d disagrees with bytes received %d.",
+		     ntohs (ip -> ip_len), buflen);
+
   /* Copy out the IP source address... */
   memcpy (&from -> sin_addr, &ip -> ip_src, 4);
 
@@ -264,7 +277,23 @@ ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
 
   if (!data) {
 	  data = buf + bufix + ip_len + sizeof *udp;
-	  len -= ip_len + sizeof *udp;
+	  len = ntohs (udp -> uh_ulen) - sizeof *udp;
+	  ++udp_packets_length_checked;
+	  if (len + data > buf + buflen) {
+		  ++udp_packets_length_overflow;
+		  if (udp_packets_length_checked > 4 &&
+		      (udp_packets_length_checked /
+		       udp_packets_length_overflow) < 2) {
+			  log_info ("%d udp packets in %d too long - dropped",
+				    udp_packets_length_overflow,
+				    udp_packets_length_checked);
+			  udp_packets_length_overflow
+				  = udp_packets_length_checked = 0;
+		  }
+		  return -1;
+	  }
+	  if (len + data != buf + buflen)
+		  log_debug ("accepting packet with data after udp payload.");
   }
 
   usum = udp -> uh_sum;
@@ -279,12 +308,15 @@ ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
 					       (u_int32_t)
 					       ntohs (udp -> uh_ulen)))));
 
+  ++udp_packets_seen;
   if (usum && usum != sum) {
-	  static int packets_seen;
-	  static int packets_bad_checksum;
-	  if (packets_seen &&
-	      (++packets_seen / ++packets_bad_checksum) < 2)
-		  log_info ("Bad udp checksum: %x %x", usum, sum);
+	  ++udp_packets_bad_checksum;
+	  if (udp_packets_seen > 4 &&
+	      (udp_packets_seen / udp_packets_bad_checksum) < 2) {
+		  log_info ("%d bad udp checksums seen in %d packets",
+			    udp_packets_bad_checksum, udp_packets_seen);
+		  udp_packets_seen = udp_packets_bad_checksum = 0;
+	  }
 	  return -1;
   }