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ctdb-common: Improve TCP packet size and offset calculations

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The IPv4 check for short packets was strange.  It appeared to ensure
that the capture included everything up to and including the window
size.  The checksum field immediately follows the window size field,
so just ensure that the packet is large enough to contain everything
up to the start of the checksum.

Add a similar check for IPv6 packets.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
This commit is contained in:
Martin Schwenke 2018-08-17 21:26:04 +10:00 committed by Amitay Isaacs
parent 43a2022596
commit 924a655b2a
1 changed files with 7 additions and 5 deletions
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12
ctdb/common/system_socket.c
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@ -768,13 +768,14 @@ static int tcp4_extract(const uint8_t *ip_pkt,
return ENOMSG;
}
/* make sure its not a short packet */
if (offsetof(struct tcphdr, th_ack) + 4 + (ip->ip_hl*4) > pktlen) {
/* Ensure there is enough of the packet to gather required fields */
if (pktlen <
(ip->ip_hl * sizeof(uint32_t)) + offsetof(struct tcphdr, th_sum)) {
return EMSGSIZE;
}
/* TCP */
tcp = (const struct tcphdr *)((ip->ip_hl*4) + (const char *)ip);
tcp = (const struct tcphdr *)(ip_pkt + (ip->ip_hl * sizeof(uint32_t)));
/* tell the caller which one we've found */
src->sin_family = AF_INET;
@ -809,7 +810,8 @@ static int tcp6_extract(const uint8_t *ip_pkt,
const struct ip6_hdr *ip6;
const struct tcphdr *tcp;
if (pktlen < sizeof(struct ip6_hdr)) {
/* Ensure there is enough of the packet to gather required fields */
if (pktlen < sizeof(struct ip6_hdr) + offsetof(struct tcphdr, th_sum)) {
return EMSGSIZE;
}
@ -822,7 +824,7 @@ static int tcp6_extract(const uint8_t *ip_pkt,
}
/* TCP */
tcp = (const struct tcphdr *)(ip6+1);
tcp = (const struct tcphdr *)(ip_pkt + sizeof(struct ip6_hdr));
/* tell the caller which one we've found */
src->sin6_family = AF_INET6;