From 3d8ccb44a6a3dc74b9bf7b765c7a2ae41f771d40 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Wed, 19 Oct 2022 11:43:48 +1100 Subject: [PATCH] Add csum_ip4_header() helper to calculate IPv4 header checksums We calculate IPv4 header checksums in at least two places, in dhcp() and in tap_ip_send. Add a helper to handle this calculation in both places. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- checksum.c | 10 ++++++++++ checksum.h | 1 + dhcp.c | 3 +-- tap.c | 3 +-- 4 files changed, 13 insertions(+), 4 deletions(-) diff --git a/checksum.c b/checksum.c index cf6fc31..7b83196 100644 --- a/checksum.c +++ b/checksum.c @@ -115,6 +115,16 @@ uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init) return (uint16_t)~csum_fold(sum_16b(buf, len) + init); } +/** + * csum_ip4_header() - Calculate and set IPv4 header checksum + * @ip4h: IPv4 header + */ +void csum_ip4_header(struct iphdr *ip4h) +{ + ip4h->check = 0; + ip4h->check = csum_unaligned(ip4h, (size_t)ip4h->ihl * 4, 0); +} + /** * csum_udp4() - Calculate and set checksum for a UDP over IPv4 packet * @udp4hr: UDP header, initialised apart from checksum diff --git a/checksum.h b/checksum.h index 2a5e915..91e9954 100644 --- a/checksum.h +++ b/checksum.h @@ -13,6 +13,7 @@ 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_ip4_header(struct iphdr *ip4h); void csum_udp4(struct udphdr *udp4hr, in_addr_t saddr, in_addr_t daddr, const void *payload, size_t len); void csum_icmp4(struct icmphdr *ih, const void *payload, size_t len); diff --git a/dhcp.c b/dhcp.c index 8dcf645..875e18b 100644 --- a/dhcp.c +++ b/dhcp.c @@ -371,8 +371,7 @@ int dhcp(const struct ctx *c, const struct pool *p) iph->tot_len = htons(len += sizeof(*iph)); iph->daddr = c->ip4.addr; iph->saddr = c->ip4.gw; - iph->check = 0; - iph->check = csum_unaligned(iph, (intptr_t)(iph->ihl * 4), 0); + csum_ip4_header(iph); len += sizeof(*eh); memcpy(eh->h_dest, eh->h_source, ETH_ALEN); diff --git a/tap.c b/tap.c index 58fc1de..de02c56 100644 --- a/tap.c +++ b/tap.c @@ -135,8 +135,7 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto, iph->daddr = c->ip4.addr_seen; memcpy(&iph->saddr, &src->s6_addr[12], 4); - iph->check = 0; - iph->check = csum_unaligned(iph, (size_t)iph->ihl * 4, 0); + csum_ip4_header(iph); memcpy(data, in, len);