[PATCH 1/2] Decode setsockopt() multicast arguments

[Ben Noordhuis]

On Sat, Feb 7, 2015 at 12:55 AM, Dmitry V. Levin <ldv at altlinux.org> wrote:
> On Thu, Feb 05, 2015 at 07:28:45PM +0100, Ben Noordhuis wrote:
>> +#ifdef IP_ADD_MEMBERSHIP
>> +static void
>> +print_mreq(struct tcb *tcp, long addr, int len)
>> +{
>> +     struct ip_mreq mreq;
>> +     if (len == sizeof(mreq) && umove(tcp, addr, &mreq) == 0) {
>> +             tprints("{imr_multiaddr=inet_addr(");
>> +             print_quoted_string(inet_ntoa(mreq.imr_multiaddr),
>> +                                 16, QUOTE_0_TERMINATED);
>> +             tprints("), imr_interface=inet_addr(");
>> +             print_quoted_string(inet_ntoa(mreq.imr_interface),
>> +                                 16, QUOTE_0_TERMINATED);
>> +             tprints(")}");
>> +     }
>> +     else {
>> +             printstr(tcp, addr, len);
>> +     }
>> +}
>
> Is there any use to print the address with printstr if length is not
> sizeof(ip_mreq) or umove has failed?  Other sockopt parsers in such
> situations just print the address in hex.

Printing the raw data helps troubleshooting more than printing a
memory address does, IMO.  printstr() is also what print_getsockopt()
and print_setsockopt() seem to fall back to.  Let me know what you
think is preferable.

I agree that there is no point calling printstr() when umove() fails,
I'll update that.