Author: markj
Date: Wed Jun 26 20:11:52 2019
New Revision: 349438
URL: https://svnweb.freebsd.org/changeset/base/349438
Log:
Avoid a divide-by-zero when bad checksum counters overflow.
A mixture of IP or UDP packets with valid and invalid checksum could
cause {ip,udp}_packets_bad_checksum to wrap around to 0, resulting
in a division by zero.
This is packet.c rev. 1.27 from OpenBSD.
admbugs: 552
Obtained from: OpenBSD
MFC after: 3 days
Modified:
head/sbin/dhclient/packet.c
Modified: head/sbin/dhclient/packet.c
==============================================================================
--- head/sbin/dhclient/packet.c Wed Jun 26 20:07:16 2019 (r349437)
+++ head/sbin/dhclient/packet.c Wed Jun 26 20:11:52 2019 (r349438)
@@ -183,7 +183,7 @@ decode_udp_ip_header(unsigned char *buf, int bufix, st
ip_packets_seen++;
if (wrapsum(checksum(buf + bufix, ip_len, 0)) != 0) {
ip_packets_bad_checksum++;
- if (ip_packets_seen > 4 &&
+ if (ip_packets_seen > 4 && ip_packets_bad_checksum != 0 &&
(ip_packets_seen / ip_packets_bad_checksum) < 2) {
note("%d bad IP checksums seen in %d packets",
ip_packets_bad_checksum, ip_packets_seen);
@@ -235,7 +235,7 @@ decode_udp_ip_header(unsigned char *buf, int bufix, st
udp_packets_seen++;
if (usum && usum != sum) {
udp_packets_bad_checksum++;
- if (udp_packets_seen > 4 &&
+ if (udp_packets_seen > 4 && udp_packets_bad_checksum != 0 &&
(udp_packets_seen / udp_packets_bad_checksum) < 2) {
note("%d bad udp checksums in %d packets",
udp_packets_bad_checksum, udp_packets_seen);
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