Hello Paul, All,
Thanks for your clarification,
I appreciate your help on this please find my reponses in line
On 9 June 2018 at 09:40, Paul de Weerd <we...@weirdnet.nl> wrote:
> Hi Tom,
>
> This is documented in ping(8):
>
> -s packetsize
> Specify the number of data bytes to be sent. The default
> is 56, which translates into 64 ICMP data bytes when
> combined with the 8 bytes of ICMP header data. The
> maximum packet size is 65467 for IPv4 and 65527 for IPv6.
>
> You can play around with the 56 bytes, but those 8 are non-negotiable:
> they're always added.
I get you ... the ICMP data bytes can be adjusted but not the ICMP
header bytes,
Note that it says 56 *data* bytes versus 64
> (total) bytes.
the issue I was highlighting is that when the user specifies
a certain size in the command , the command says
sending 1000 bytes
but then says the reply 1008 bytes
I think this is confusing to the user of the system.
also I think the total bytes is incorrect because it only takes
account of the ICMP header and not the IP header,
Perhaps the Approach I should take to fix this (my confusion)
( and possibly future users confusion)
would be to make the displayed values consistent and the
displayed label consistent
>
> You seem to be misunderstanding the format string passed that you
> found. %d is part of a format string, see printf(3). The "%"
> indicates a conversion specification, the "d" indicates the type of
> conversion, in this case a signed integer. The arguments following
> the format string are filled in where a conversion specification is
> given in the format string, in the order given. So in this example:
>
> #include <stdio.h>;
>
> int main() {
> int number;
> const char* test;
>
> text = "Hi Tom!";
> number = 42;
>
> printf("string: %s\nnumber: %d\n", string, number)
> return 0;
> }
>
> The printf(3) function gets called with three arguments. The first is
> the format string: "string: %s\nnumber: %d\n". As you can see,
> there's two conversion specifications in there, "%s" and "%d". "%s"
> is for a "char*" argument, it gets replaced with the second argument
> to the function (the variable 'string', which we gave the value "Hi
> Tom!"). "%d" is for the integer argument, it gets replaced with a
> decimal representation of the value of the third argument to the
> function (the variable 'number', which we gave the value 42).
>
Thanks for your help on printf(3) :) Ill work on this
> Applying this knowledge to the three lines you found in the ping
> source:
> In line 760, %d gets the value from variable 'datalen'.
> In lines 1248 and 1292, %d gets the value from variable 'cc'.
>
> Note that 'cc' could be changed between those two lines, so the value
> printed in the end doesn't *have* to be the same - that depends on the
> rest of the code.
I think we could display (datalen+8) bytes in line 760
or
preferably display (cc -8) bytes in lines 1248 and 1292
and do a ping man page update based on the agreed approach
thanks for your help and input
Tom Smyth
>
> Cheers,
>
> Paul
>
> --
>>++++++++[<++++++++++>-]<+++++++.>+++[<------>-]<.>+++[<+
> +++++++++++>-]<.>++[<------------>-]<+.--------------.[-]
> http://www.weirdnet.nl/
--
Kindest regards,
Tom Smyth
