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Add csum_udp6() helper for calculating UDP over IPv6 checksums

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Add a helper for calculating UDP checksums when used over IPv6
For future flexibility, the new helper takes parameters for the fields in
the IPv6 pseudo-header, so an IPv6 header or pseudo-header doesn't need to
be explicitly constructed.  It also allows the UDP header and payload to
be in separate buffers, although we don't use this yet.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2022-10-19 11:43:46 +11:00 committed by Stefano Brivio
parent 67ab617172
commit 6905ac75ec
3 changed files with 28 additions and 3 deletions
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22
checksum.c
View file

@ -52,6 +52,7 @@
#include <stddef.h>
#include <stdint.h>
#include <linux/udp.h>
#include <linux/icmp.h>
#include <linux/icmpv6.h>
@ -123,6 +124,27 @@ void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len)
icmp4hr->checksum = csum_unaligned(payload, len, psum);
}
/**
* csum_udp6() - Calculate and set checksum for a UDP over IPv6 packet
* @udp6hr: UDP header, initialised apart from checksum
* @payload: UDP packet payload
* @len: Length of @payload (not including UDP header)
*/
void csum_udp6(struct udphdr *udp6hr,
const struct in6_addr *saddr, const struct in6_addr *daddr,
const void *payload, size_t len)
{
/* Partial checksum for the pseudo-IPv6 header */
uint32_t psum = sum_16b(saddr, sizeof(*saddr)) +
sum_16b(daddr, sizeof(*daddr)) +
htons(len + sizeof(*udp6hr)) + htons(IPPROTO_UDP);
udp6hr->check = 0;
/* Add in partial checksum for the UDP header alone */
psum += sum_16b(udp6hr, sizeof(*udp6hr));
udp6hr->check = csum_unaligned(payload, len, psum);
}
/**
* csum_icmp6() - Calculate and set checksum for an ICMPv6 packet
* @icmp6hr: ICMPv6 header, initialised apart from checksum

4
checksum.h
View file

@ -6,6 +6,7 @@
#ifndef CHECKSUM_H
#define CHECKSUM_H
struct udphdr;
struct icmphdr;
struct icmp6hdr;
@ -13,6 +14,9 @@ uint32_t sum_16b(const void *buf, size_t len);
uint16_t csum_fold(uint32_t sum);
uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init);
void csum_icmp4(struct icmphdr *ih, const void *payload, size_t len);
void csum_udp6(struct udphdr *udp6hr,
const struct in6_addr *saddr, const struct in6_addr *daddr,
const void *payload, size_t len);
void csum_icmp6(struct icmp6hdr *icmp6hr,
const struct in6_addr *saddr, const struct in6_addr *daddr,
const void *payload, size_t len);

5
tap.c
View file

@ -183,9 +183,8 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
} else if (proto == IPPROTO_UDP) {
struct udphdr *uh = (struct udphdr *)(ip6h + 1);
uh->check = 0;
uh->check = csum_unaligned(ip6h, len + sizeof(*ip6h),
0);
csum_udp6(uh, &ip6h->saddr, &ip6h->daddr,
uh + 1, len - sizeof(*uh));
} else if (proto == IPPROTO_ICMPV6) {
struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);