From 67ab6171729cfcf7867cbb92a2099d88d86f6e6b Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 19 Oct 2022 11:43:45 +1100 Subject: Add csum_icmp4() helper for calculating ICMP checksums Although tap_ip_send() is currently the only place calculating ICMP checksums, create a helper function for symmetry with ICMPv6. For future flexibility it allows the ICMPv6 header and payload to be in separate buffers. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- checksum.c | 16 ++++++++++++++++ checksum.h | 2 ++ tap.c | 4 +--- 3 files changed, 19 insertions(+), 3 deletions(-) diff --git a/checksum.c b/checksum.c index 78c6960..f35c948 100644 --- a/checksum.c +++ b/checksum.c @@ -52,6 +52,7 @@ #include #include +#include #include /** @@ -107,6 +108,21 @@ uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init) return (uint16_t)~csum_fold(sum_16b(buf, len) + init); } +/** + * csum_icmp4() - Calculate and set checksum for an ICMP packet + * @icmp4hr: ICMP header, initialised apart from checksum + * @payload: ICMP packet payload + * @len: Length of @payload (not including ICMP header) + */ +void csum_icmp4(struct icmphdr *icmp4hr, const void *payload, size_t len) +{ + /* Partial checksum for ICMP header alone */ + uint32_t psum = sum_16b(icmp4hr, sizeof(*icmp4hr)); + + icmp4hr->checksum = 0; + icmp4hr->checksum = 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 d7daabf..bf0620f 100644 --- a/checksum.h +++ b/checksum.h @@ -6,11 +6,13 @@ #ifndef CHECKSUM_H #define CHECKSUM_H +struct icmphdr; struct icmp6hdr; 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_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 aafc92b..f082901 100644 --- a/tap.c +++ b/tap.c @@ -148,9 +148,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, uh->check = 0; } else if (iph->protocol == IPPROTO_ICMP) { struct icmphdr *ih = (struct icmphdr *)(iph + 1); - - ih->checksum = 0; - ih->checksum = csum_unaligned(ih, len, 0); + csum_icmp4(ih, ih + 1, len - sizeof(*ih)); } if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh), 1) < 0) -- cgit v1.2.3