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(a)gibson.dropbear.id.au>
---
checksum.c | 6 ++++++
checksum.h | 1 +
dhcp.c | 3 +--
tap.c | 3 +--
4 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/checksum.c b/checksum.c
index 72f1cfb..f25a96a 100644
--- a/checksum.c
+++ b/checksum.c
@@ -114,6 +114,12 @@ uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init)
return (uint16_t)~csum_fold(sum_16b(buf, len) + init);
}
+void csum_ip4_header(struct iphdr *ip4hr)
+{
+ ip4hr->check = 0;
+ ip4hr->check = csum_unaligned(ip4hr, (size_t)ip4hr->ihl * 4, 0);
+}
+
/**
* csum_udp4() - Calculate checksum for a UDP over IPv4 packet
* @udp4hr: UDP header, initialized apart from checksum
diff --git a/checksum.h b/checksum.h
index a9502b9..bdb2ed2 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 *ip4hr);
void csum_udp4(struct udphdr *udp4hr,
in_addr_t saddr, in_addr_t daddr,
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);
--
2.37.3