On Fri, Jun 08, 2018 at 08:52:17PM +0100, Tom Smyth wrote:
> Hello I see a small discrepancy between the measurement
> of sent and received packets as displayed by ping command
>
> on the wire the sent and received packets are the same size
> I had a brief go
>
> foo# ping 5.134.88.1
> PING 5.134.88.1 (5.134.88.1): 56 data bytes
> 64 bytes from 5.134.88.1: icmp_seq=0 ttl=53 time=91.719 ms
>
> it would appear that one measurement is the ICMP Payload only
> and the other is the ICMP payload + ICMP header (8 byte difference)
>
This analysis is correct.
This discrepancy always bugged me but I suspect that people got so
used to it that changing it is a bad idea. I certainly do the math
automatically in my head.
I'd like to improve this but I don't think it's possible, this stuff
is just around for too long to change.
>
> foo# grep -n " data bytes" /root/ping.c
> 760: printf("%s): %d data bytes\n", pr_addr(dst, dst->sa_len), datalen);
> foo# grep -n " bytes from" /root/ping.c
> 1248: printf("%d bytes from %s: icmp_seq=%u", cc,
> 1292: printf("%d bytes from %s: ", cc, pr_addr(from, fromlen));
>
> looking at the source code it looks like the size = %d but %d is presenting
> different values
> I didnt see where %d was being changed between line 760 and line 1248
> It has been a while since I looked at C programming in anger and im a bit
> rusty...
> any pointers on where i should be looking so that I can submit a patch
>
> --
> Kindest regards,
> Tom Smyth
>
--
I'm not entirely sure you are real.
