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 <david(a)gibson.dropbear.id.au>
---
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 <stddef.h>
#include <stdint.h>
+#include <linux/icmp.h>
#include <linux/icmpv6.h>
/**
@@ -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)
--
2.37.3