* [PATCH] checksum: Fix calculation for ICMP checksum on IPv4
@ 2022-10-25 16:07 Stefano Brivio
2022-10-25 17:25 ` Stefano Brivio
2022-10-26 0:06 ` David Gibson
0 siblings, 2 replies; 6+ messages in thread
From: Stefano Brivio @ 2022-10-25 16:07 UTC (permalink / raw)
To: passt-dev; +Cc: Paul Holzinger, David Gibson
We need to zero out the checksum field before calculating the
checksum, of course. I have no idea how this passed the "icmp" test
set, looking into it.
Reported-by: Paul Holzinger <pholzing@redhat.com>
Fixes: 67ab6171729c ("Add csum_icmp4() helper for calculating ICMP checksums")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
checksum.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/checksum.c b/checksum.c
index 09d2c7c..c59869c 100644
--- a/checksum.c
+++ b/checksum.c
@@ -160,10 +160,13 @@ void csum_udp4(struct udphdr *udp4hr, in_addr_t saddr, in_addr_t daddr,
*/
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));
+ uint32_t psum;
icmp4hr->checksum = 0;
+
+ /* Partial checksum for ICMP header alone */
+ psum = sum_16b(icmp4hr, sizeof(*icmp4hr));
+
icmp4hr->checksum = csum_unaligned(payload, len, psum);
}
--
@@ -160,10 +160,13 @@ void csum_udp4(struct udphdr *udp4hr, in_addr_t saddr, in_addr_t daddr,
*/
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));
+ uint32_t psum;
icmp4hr->checksum = 0;
+
+ /* Partial checksum for ICMP header alone */
+ psum = sum_16b(icmp4hr, sizeof(*icmp4hr));
+
icmp4hr->checksum = csum_unaligned(payload, len, psum);
}
--
2.35.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] checksum: Fix calculation for ICMP checksum on IPv4
2022-10-25 16:07 [PATCH] checksum: Fix calculation for ICMP checksum on IPv4 Stefano Brivio
@ 2022-10-25 17:25 ` Stefano Brivio
2022-10-26 0:06 ` David Gibson
1 sibling, 0 replies; 6+ messages in thread
From: Stefano Brivio @ 2022-10-25 17:25 UTC (permalink / raw)
To: passt-dev; +Cc: Paul Holzinger, David Gibson
On Tue, 25 Oct 2022 18:07:13 +0200
Stefano Brivio <sbrivio@redhat.com> wrote:
> We need to zero out the checksum field before calculating the
> checksum, of course. I have no idea how this passed the "icmp" test
> set, looking into it.
That's because the version of ping(8) I use on my test machine, from
'iputils', ignores a failed checksum in the reply:
https://github.com/iputils/iputils/blob/59908434d7505ef574c2e0811ad1d5edb671845a/ping/ping.c#L1544
...the parameter 'csfailed' in gather_statistics() is just passed as 0
here. The checksum was actually wrong in the CI test run.
Forcing a specific version (e.g. from GNU inetutils) looks rather messy
and non-portable, so I'm afraid there isn't much we can do for this,
other than being careful.
--
Stefano
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] checksum: Fix calculation for ICMP checksum on IPv4
2022-10-25 16:07 [PATCH] checksum: Fix calculation for ICMP checksum on IPv4 Stefano Brivio
2022-10-25 17:25 ` Stefano Brivio
@ 2022-10-26 0:06 ` David Gibson
[not found] ` <CAFsF8v+x-c=Rk6z+-hwwFWt0PvEu10u-rpkQ4F=Z2jbfAJPoww@mail.gmail.com>
1 sibling, 1 reply; 6+ messages in thread
From: David Gibson @ 2022-10-26 0:06 UTC (permalink / raw)
To: Stefano Brivio; +Cc: passt-dev, Paul Holzinger
[-- Attachment #1: Type: text/plain, Size: 1438 bytes --]
On Tue, Oct 25, 2022 at 06:07:13PM +0200, Stefano Brivio wrote:
> We need to zero out the checksum field before calculating the
> checksum, of course. I have no idea how this passed the "icmp" test
> set, looking into it.
>
> Reported-by: Paul Holzinger <pholzing@redhat.com>
> Fixes: 67ab6171729c ("Add csum_icmp4() helper for calculating ICMP checksums")
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Oops, that's embarrassing.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> ---
> checksum.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/checksum.c b/checksum.c
> index 09d2c7c..c59869c 100644
> --- a/checksum.c
> +++ b/checksum.c
> @@ -160,10 +160,13 @@ void csum_udp4(struct udphdr *udp4hr, in_addr_t saddr, in_addr_t daddr,
> */
> 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));
> + uint32_t psum;
>
> icmp4hr->checksum = 0;
> +
> + /* Partial checksum for ICMP header alone */
> + psum = sum_16b(icmp4hr, sizeof(*icmp4hr));
> +
> icmp4hr->checksum = csum_unaligned(payload, len, psum);
> }
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-10-26 14:28 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2022-10-25 16:07 [PATCH] checksum: Fix calculation for ICMP checksum on IPv4 Stefano Brivio
2022-10-25 17:25 ` Stefano Brivio
2022-10-26 0:06 ` David Gibson
[not found] ` <CAFsF8v+x-c=Rk6z+-hwwFWt0PvEu10u-rpkQ4F=Z2jbfAJPoww@mail.gmail.com>
2022-10-26 12:57 ` Stefano Brivio
[not found] ` <CAFsF8vLk_Qyva32Z5pH5Jic+NeFKrnaPLm_pw_QDARfjdiXQvQ@mail.gmail.com>
2022-10-26 13:40 ` Stefano Brivio
2022-10-26 14:28 ` Stefano Brivio
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