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Diffstat (limited to 'contrib/isc-dhcp/common/packet.c')
-rw-r--r--contrib/isc-dhcp/common/packet.c84
1 files changed, 58 insertions, 26 deletions
diff --git a/contrib/isc-dhcp/common/packet.c b/contrib/isc-dhcp/common/packet.c
index 069a76b81762..b5ad42748b5f 100644
--- a/contrib/isc-dhcp/common/packet.c
+++ b/contrib/isc-dhcp/common/packet.c
@@ -42,7 +42,7 @@
#ifndef lint
static char copyright[] =
-"$Id: packet.c,v 1.18.2.1 1998/06/26 18:20:44 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium. All rights reserved.\n";
+"$Id: packet.c,v 1.18.2.4 1999/04/24 15:31:47 mellon Exp $ Copyright (c) 1996 The Internet Software Consortium. All rights reserved.\n";
#endif /* not lint */
#include "dhcpd.h"
@@ -72,6 +72,9 @@ u_int32_t checksum (buf, nbytes, sum)
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 @@ u_int32_t checksum (buf, nbytes, sum)
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 @@ u_int32_t wrapsum (sum)
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
@@ -194,17 +189,15 @@ void assemble_udp_ip_header (interface, buf, bufix,
/* Compute UDP checksums, including the ``pseudo-header'', the UDP
header and the data. */
-#if 0
udp.uh_sum =
wrapsum (checksum ((unsigned char *)&udp, sizeof udp,
checksum (data, len,
checksum ((unsigned char *)
&ip.ip_src,
- sizeof ip.ip_src,
+ 2 * sizeof ip.ip_src,
IPPROTO_UDP +
(u_int32_t)
ntohs (udp.uh_ulen)))));
-#endif
/* Copy the udp header into the buffer... */
memcpy (&buf [*bufix], &udp, sizeof udp);
@@ -239,18 +232,25 @@ 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);
@@ -266,12 +266,23 @@ ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
#endif /* USERLAND_FILTER */
/* Check the IP header checksum - it should be zero. */
+ ++ip_packets_seen;
if (wrapsum (checksum (buf + bufix, ip_len, 0))) {
- 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);
@@ -281,10 +292,25 @@ 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 + 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.");
}
-#if 0
usum = udp -> uh_sum;
udp -> uh_sum = 0;
@@ -292,16 +318,22 @@ ssize_t decode_udp_ip_header (interface, buf, bufix, from, data, len)
checksum (data, len,
checksum ((unsigned char *)
&ip -> ip_src,
- sizeof ip -> ip_src,
+ 2 * sizeof ip -> ip_src,
IPPROTO_UDP +
(u_int32_t)
ntohs (udp -> uh_ulen)))));
+ udp_packets_seen++;
if (usum && usum != sum) {
- 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;
}
-#endif
/* Copy out the port... */
memcpy (&from -> sin_port, &udp -> uh_sport, sizeof udp -> uh_sport);
generated by cgit v1.2.3 (git 2.25.1) at 2025-10-05 01:19:23 +0000