Subject: Re: [PATCH bpf 1/3] selftests/xsk: print correct payload for packet dump

From: Maciej Fijalkowski <[email-masked]>
Date: Tue, 15 Nov 2022 13:29:26 +0100

On Tue, Nov 15, 2022 at 09:05:36AM +0100, Magnus Karlsson wrote:
> From: Magnus Karlsson <[email-masked]>
> 
> Print the correct payload when the packet dump option is selected. The
> network to host conversion was forgotten and the payload was
> erronously declared to be an int instead of an unsigned int. Changed
> the loop index i too, as it does not need to be an int and was
> declared on the same row.
> 
> The printout looks something like this after the fix:
> 
> DEBUG>> L2: dst mac: 000A569EEE62
> DEBUG>> L2: src mac: 000A569EEE61
> DEBUG>> L3: ip_hdr->ihl: 05
> DEBUG>> L3: ip_hdr->saddr: 192.168.100.161
> DEBUG>> L3: ip_hdr->daddr: 192.168.100.162
> DEBUG>> L4: udp_hdr->src: 2121
> DEBUG>> L4: udp_hdr->dst: 2020
> DEBUG>> L5: payload: 4
> ---------------------------------------

Above would be helpful if previous output was included as well but not a
big deal i guess.

> 
> Fixes: facb7cb2e909 ("selftests/bpf: Xsk selftests - SKB POLL, NOPOLL")
> Signed-off-by: Magnus Karlsson <[email-masked]>
> ---
>  tools/testing/selftests/bpf/xskxceiver.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/xskxceiver.c b/tools/testing/selftests/bpf/xskxceiver.c
> index 681a5db80dae..51e693318b3f 100644
> --- a/tools/testing/selftests/bpf/xskxceiver.c
> +++ b/tools/testing/selftests/bpf/xskxceiver.c
> @@ -767,7 +767,7 @@ static void pkt_dump(void *pkt, u32 len)
>  	struct ethhdr *ethhdr;
>  	struct udphdr *udphdr;
>  	struct iphdr *iphdr;
> -	int payload, i;
> +	u32 payload, i;
>  
>  	ethhdr = pkt;
>  	iphdr = pkt + sizeof(*ethhdr);
> @@ -792,7 +792,7 @@ static void pkt_dump(void *pkt, u32 len)
>  	fprintf(stdout, "DEBUG>> L4: udp_hdr->src: %d\n", ntohs(udphdr->source));
>  	fprintf(stdout, "DEBUG>> L4: udp_hdr->dst: %d\n", ntohs(udphdr->dest));
>  	/*extract L5 frame */
> -	payload = *((uint32_t *)(pkt + PKT_HDR_SIZE));
> +	payload = ntohl(*((u32 *)(pkt + PKT_HDR_SIZE)));
>  
>  	fprintf(stdout, "DEBUG>> L5: payload: %d\n", payload);
>  	fprintf(stdout, "---------------------------------------\n");
> -- 
> 2.34.1
>