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Add csum_ip4_header() helper to calculate IPv4 header checksums

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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 <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2022-10-19 11:43:48 +11:00 committed by Stefano Brivio
parent bd4be308fc
commit 3d8ccb44a6
4 changed files with 13 additions and 4 deletions
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10
checksum.c
View file

@ -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

1
checksum.h
View file

@ -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);

3
dhcp.c
View file

@ -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);

3
tap.c
View file

@ -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);