[src/netbsd-1-4]: src/usr.sbin/dhcp/common Pull up 1.1.1.6 (fix packet checks...

[mellon <mellon%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0ea774d3bfb0
branches:  netbsd-1-4
changeset: 468489:0ea774d3bfb0
user:      mellon <mellon%NetBSD.org@localhost>
date:      Mon Apr 26 16:40:45 1999 +0000

description:
Pull up 1.1.1.6 (fix packet checksum bug)

diffstat:

 usr.sbin/dhcp/common/packet.c |  84 ++++++++++++++++++++++++++++--------------
 1 files changed, 56 insertions(+), 28 deletions(-)

diffs (163 lines):

diff -r 06d4255797c8 -r 0ea774d3bfb0 usr.sbin/dhcp/common/packet.c
--- a/usr.sbin/dhcp/common/packet.c     Mon Apr 26 16:35:21 1999 +0000
+++ b/usr.sbin/dhcp/common/packet.c     Mon Apr 26 16:40:45 1999 +0000
@@ -42,7 +42,7 @@
 
 #ifndef lint
 static char copyright[] =
-"$Id: packet.c,v 1.1.1.5 1999/03/26 17:49:22 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium.  All rights reserved.\n";
+"$Id: packet.c,v 1.1.1.5.2.1 1999/04/26 16:40:45 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium.  All rights reserved.\n";
 #endif /* not lint */
 
 #include "dhcpd.h"
@@ -72,6 +72,9 @@
                debug ("sum = %x", sum);
 #endif
                sum += (u_int16_t) ntohs(*((u_int16_t *)(buf + i)));
+               /* Add carry. */
+               if (sum > 0xFFFF)
+                       sum -= 0xFFFF;
        }       
 
        /* If there's a single byte left over, checksum it, too.   Network
@@ -81,13 +84,15 @@
                debug ("sum = %x", sum);
 #endif
                sum += buf [i] << 8;
+               /* Add carry. */
+               if (sum > 0xFFFF)
+                       sum -= 0xFFFF;
        }
        
        return sum;
 }
 
-/* Fold the upper sixteen bits of the checksum down into the lower bits,
-   complement the sum, and then put it into network byte order. */
+/* Finish computing the sum, and then put it into network byte order. */
 
 u_int32_t wrapsum (sum)
        u_int32_t sum;
@@ -96,17 +101,7 @@
        debug ("wrapsum (%x)", sum);
 #endif
 
-       while (sum > 0x10000) {
-               sum = (sum >> 16) + (sum & 0xFFFF);
-#ifdef DEBUG_CHECKSUM_VERBOSE
-               debug ("sum = %x", sum);
-#endif
-               sum += (sum >> 16);
-#ifdef DEBUG_CHECKSUM_VERBOSE
-               debug ("sum = %x", sum);
-#endif
-       }
-       sum = sum ^ 0xFFFF;
+       sum = ~sum & 0xFFFF;
 #ifdef DEBUG_CHECKSUM_VERBOSE
        debug ("sum = %x", sum);
 #endif
@@ -237,20 +232,25 @@
 
 /* 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 packets_seen;
-  static int packets_bad_checksum;
+  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);
@@ -266,14 +266,23 @@
 #endif /* USERLAND_FILTER */
 
   /* Check the IP header checksum - it should be zero. */
+  ++ip_packets_seen;
   if (wrapsum (checksum (buf + bufix, ip_len, 0))) {
-         if (packets_seen &&
-             (++packets_seen / ++packets_bad_checksum) < 2)
-                 note ("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) {
+                 note ("%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)
+         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);
 
@@ -283,7 +292,23 @@
 
   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 + bufix + buflen) {
+                 ++udp_packets_length_overflow;
+                 if (udp_packets_length_checked > 4 &&
+                     (udp_packets_length_checked /
+                      udp_packets_length_overflow) < 2) {
+                         note ("%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 + bufix + buflen)
+                 debug ("accepting packet with data after udp payload.");
   }
 
   usum = udp -> uh_sum;
@@ -298,12 +323,15 @@
                                               (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)
-                 note ("Bad udp checksum: %x %x", usum, sum);
+         udp_packets_bad_checksum++;
+         if (udp_packets_seen > 4 &&
+             (udp_packets_seen / udp_packets_bad_checksum) < 2) {
+                 note ("%d bad udp checksums in %d packets",
+                       udp_packets_bad_checksum, udp_packets_seen);
+                 udp_packets_seen = udp_packets_bad_checksum = 0;
+         }
          return -1;
   }