On Sat, 17 Feb 2024 16:07:22 +0100
Laurent Vivier <lvivier(a)redhat.com> wrote:
We can find the same function to compute the IPv4
header
checksum in tcp.c, udp.c and tap.c
Use the function defined for tap.c, csum_ip4_header(), but
with the code used in tcp.c and udp.c as it doesn't need a fully
initialiazed IPv4 header, only protocol, tot_len, saddr and daddr.
Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
Notes:
v3:
- function parameters provide tot_len, saddr, daddr and protocol
rather than an iphdr
v2:
- use csum_ip4_header() from checksum.c
- use code from tcp.c and udp.c in csum_ip4_header()
- use "const struct iphfr *", check is not updated by the
function but by the caller.
checksum.c | 17 +++++++++++++----
checksum.h | 3 ++-
tap.c | 3 ++-
tcp.c | 24 +++---------------------
udp.c | 20 ++------------------
5 files changed, 22 insertions(+), 45 deletions(-)
diff --git a/checksum.c b/checksum.c
index 74e3742bc6f6..511b296a9a80 100644
--- a/checksum.c
+++ b/checksum.c
@@ -57,6 +57,7 @@
#include <linux/icmpv6.h>
#include "util.h"
+#include "ip.h"
#include "checksum.h"
/* Checksums are optional for UDP over IPv4, so we usually just set
@@ -116,13 +117,21 @@ uint16_t csum_fold(uint32_t sum)
uint16_t csum(const void *buf, size_t len, uint32_t init);
/**
- * csum_ip4_header() - Calculate and set IPv4 header checksum
+ * csum_ip4_header() - Calculate IPv4 header checksum
* @ip4h: IPv4 header
*/
-void csum_ip4_header(struct iphdr *ip4h)
+uint16_t csum_ip4_header(uint16_t tot_len, uint8_t protocol,
+ uint32_t saddr, uint32_t daddr)
{
- ip4h->check = 0;
- ip4h->check = csum(ip4h, (size_t)ip4h->ihl * 4, 0);
+ uint32_t sum = L2_BUF_IP4_PSUM(protocol);
Now that we use this macro, Coverity Scan realises that it's broken:
#define L2_BUF_IP4_PSUM(proto) ((uint32_t)htons_constant(0x4500) + \
(uint32_t)htons_constant(0xff00 | (proto)))
...but proto is eight (lower) bits, so this actually ignores 'proto'.