From 6905ac75ec6643fbc93963ad9ded4903e8eeebf0 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 19 Oct 2022 11:43:46 +1100 Subject: Add csum_udp6() helper for calculating UDP over IPv6 checksums 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 Signed-off-by: Stefano Brivio --- checksum.c | 22 ++++++++++++++++++++++ checksum.h | 4 ++++ tap.c | 5 ++--- 3 files changed, 28 insertions(+), 3 deletions(-) diff --git a/checksum.c b/checksum.c index f35c948..175381d 100644 --- a/checksum.c +++ b/checksum.c @@ -52,6 +52,7 @@ #include #include +#include #include #include @@ -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 diff --git a/checksum.h b/checksum.h index bf0620f..2bb2ff9 100644 --- a/checksum.h +++ b/checksum.h @@ -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); diff --git a/tap.c b/tap.c index f082901..9c197cb 100644 --- a/tap.c +++ b/tap.c @@ -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); -- cgit v1.2.3