[Toybox] [PATCH] ping: fix -q behavior.

[enh]

(To be clear: I'm not feeding you the answer in pieces... I only know
pieces of the answer. If I knew what the code should look like, I'd send a
patch 😁)

On Tue, Jul 10, 2018, 15:56 enh <enh at google.com> wrote:

> > why/how does ping ::1 work
>
> link-local addresses
> (https://tools.ietf.org/html/rfc4291?referring_site=bodynav#section-2.5.6)
> are unrelated to the loopback address
> (https://tools.ietf.org/html/rfc4291?referring_site=bodynav#section-2.5.3
> ).
>
> ping6 with just -I should not work, but ping6 with just % should.
> (both together is fine too.) sin6_scope_id needs to be set to
> correspond to the interface.
>
> IPv6 is a sizeable bag of worms.
> On Mon, Jul 9, 2018 at 4:42 PM Rob Landley <rob at landley.net> wrote:
> >
> >
> >
> > On 07/09/2018 04:49 PM, enh wrote:
> > > On Fri, Jul 6, 2018 at 6:16 PM Rob Landley <rob at landley.net> wrote:
> > >>
> > >> On 07/06/2018 03:19 PM, enh wrote:
> > >>> they said they'd be much more worried about whether we use IP_RECVERR
> > >>> and parse ICMP errors correctly,
> > >>
> > >> I don't think we do but I'll throw it on the todo heap. I'm not 100%
> sure what
> > >> "correctly" means here, but I can try to research it.
> > >>
> > >>> or do link-local ping correctly...
> > >>
> > >> Again, define "correctly"...?
> > >>
> > >> (I can ping ::1 and ping 127.0.0.1 but I dunno if it's doing
> something wrong?)
> > >
> > > https://en.wikipedia.org/wiki/Link-local_address#IPv6
> >
> > This can of worms?
> >
> > https://twitter.com/RichFelker/status/982286128593043456
> >
> > (I've always considered ipv6 a poster child for the second system
> effect.)
> >
> > > try `ifconfig -a | grep link`
> >
> > No output. (Using ubuntu's ifconfig or toybox's.) Ah: case insensitive
> grep.
> >
> > > and then compare `ping6 $that_address`
> > > (which should fail) against `ping6 -I $that_interface $that_address`
> >
> > Sigh. I had -I working at one point... wait,
> >
> >   printf("ntop=%s\n", ntop(sa));
> >   if (TT.I && bind(TT.sock, sa, sizeof(src_addr))) perror_exit("bind");
> >
> > $ ./ping -I wlan0 fe80::6627:37ff:fe21:64bf
> > ntop=fe80::6627:37ff:fe21:64bf
> > Ping fe80::6627:37ff:fe21:64bf (fe80::6627:37ff:fe21:64bf) from wlan0
> > (fe80::6627:37ff:fe21:64bf): 56(84) bytes.
> > ping: sendto: Invalid argument
> >
> > What am I doing wrong? I'm binding to the same IP address I'm trying to
> ping,
> > how is sendto() giving me an invalid argument error? strace says:
> >
> > socket(PF_INET6, SOCK_DGRAM, IPPROTO_ICMPV6) = 3
> > bind(3, {sa_family=AF_INET6, sin6_port=htons(0), inet_pton(AF_INET6,
> > "fe80::6627:37ff:fe21:64bf", &sin6_addr), sin6_flowinfo=0,
> > sin6_scope_id=if_nametoindex("wlan0")}, 28) = 0
> > sendto(3,
> >
> "\200\0002(\236+\1\0000\311\3412\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
> > 64, 0, {sa_family=AF_INET6, sin6_port=htons(0), inet_pton(AF_INET6,
> > "fe80::6627:37ff:fe21:64bf", &sin6_addr), sin6_flowinfo=0,
> sin6_scope_id=0}, 28)
> > = -1 EINVAL (Invalid argument)
> >
> > Opened with v6, bound with v6... Sigh, do I have the destination packet
> > misformatted for v6? If so, why/how does ping ::1 work?
> >
> > Hmmm... And this is why I have systems built for qemu, so I can STICK
> PRINTKs
> > INTO THE KERNEL. Grrr...
> >
> > > and `ping6 $that_address%$that_interface`.
> >
> > I'm guessing percent is a synonym for -I so this is basically the same
> issue,
> > modulo implementing %?
> >
> > Rob
>
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