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Use UDP len when calculating UDP checksums

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The length of the IP payload is normally equal to the UDP length, UDP Options
(draft-ietf-tsvwg-udp-options-02) suggests using the difference between IP
length and UDP length to create space for trailing data.

Correct checksum length calculation to use the UDP length rather than the IP
length when not offloading UDP checksums.

Approved by: jtl (mentor)
Differential Revision:	https://reviews.freebsd.org/D15222
This commit is contained in:
Tom Jones 2018-06-06 07:04:40 +00:00
parent bca1b45bb1
commit 1fdbfb909f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=334705
1 changed files with 23 additions and 5 deletions
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28
sys/netinet/ip_output.c
View File

@ -80,6 +80,10 @@ __FBSDID("$FreeBSD$");
#include <netinet/in_var.h>
#include <netinet/ip_var.h>
#include <netinet/ip_options.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#ifdef SCTP
#include <netinet/sctp.h>
#include <netinet/sctp_crc32.h>
@ -920,14 +924,28 @@ void
in_delayed_cksum(struct mbuf *m)
{
struct ip *ip;
uint16_t csum, offset, ip_len;
struct udphdr *uh;
uint16_t cklen, csum, offset;
ip = mtod(m, struct ip *);
offset = ip->ip_hl << 2 ;
ip_len = ntohs(ip->ip_len);
csum = in_cksum_skip(m, ip_len, offset);
if (m->m_pkthdr.csum_flags & CSUM_UDP && csum == 0)
csum = 0xffff;
if (m->m_pkthdr.csum_flags & CSUM_UDP) {
/* if udp header is not in the first mbuf copy udplen */
if (offset + sizeof(struct udphdr) > m->m_len)
m_copydata(m, offset + offsetof(struct udphdr, uh_ulen),
2, (caddr_t)&cklen);
else {
uh = (struct udphdr *)((caddr_t)ip + offset);
cklen = ntohs(uh->uh_ulen);
}
csum = in_cksum_skip(m, cklen + offset, offset);
if (csum == 0)
csum = 0xffff;
} else {
cklen = ntohs(ip->ip_len);
csum = in_cksum_skip(m, cklen, offset);
}
offset += m->m_pkthdr.csum_data; /* checksum offset */
/* find the mbuf in the chain where the checksum starts*/