Hello!
On Saturday 02 January 2021 19:04:06 Alejandro Colomar (man-pages) wrote:
> Hi Pali,
>
> Please, see some comments below.
>
> On 1/2/21 3:02 PM, Pali Rohár wrote:
> > Also add description for struct in6_ifreq which is used for IPv6 addresses.
> >
> > SIOCSIFADDR and SIOCDIFADDR can be used to add or delete IPv6 address and
> > pppd is using these ioctls for a long time. Surprisingly SIOCDIFADDR cannot
> > be used for deleting IPv4 address but only for IPv6 addresses.
> >
> > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> > ---
> > man7/netdevice.7 | 36 +++++++++++++++++++++++++++++-------
> > 1 file changed, 29 insertions(+), 7 deletions(-)
> >
> > diff --git a/man7/netdevice.7 b/man7/netdevice.7
> > index 488e83d9a..5b68e4988 100644
> > --- a/man7/netdevice.7
> > +++ b/man7/netdevice.7
> > @@ -55,9 +55,27 @@ struct ifreq {
> > .EE
> > .in
> > .PP
> > +Exception is
> > +.B AF_INET6
> > +socket for which is used
> > +.I in6_ifreq
> > +structure:
>
> Wording fix:
>
> [
> AF_INET6 is an exception.
> It passes an
> .I in6_ifreq
> structure:
> ]
Ok, I will fix it.
> Are there more exceptions?
> Or is it the only one?
I really do not know. I played only with the IPv4 and IPv6 sockets.
I come across this incompatibility during reading pppd source code that
it has different structures for IPv4 and IPv6 which are passed to
SIOCSIFADDR ioctl.
> > +.PP
> > +.in +4n
> > +.EX
> > +struct in6_ifreq {
> > + struct in6_addr ifr6_addr;
> > + u32 ifr6_prefixlen;
> > + int ifr6_ifindex; /* Interface index */
> > +};
> > +.EE
> > +.in
> > +.PP
> > Normally, the user specifies which device to affect by setting
> > .I ifr_name
> > -to the name of the interface.
> > +to the name of the interface or
> > +.I ifr6_ifindex
> > +to the index of the interface.
>
> I've seen there's ifr_ifindex too (see SIOCGIFNAME).
> Can it be used in the same way as ifr6_ifindex?
Sorry, I do not know too. In all applications I saw that they are using
ifr_name for IPv4 stuff.
This needs to be tested if ifr_ifindex instead of ifr_name works for
specifying IPv4 address.
> > All other members of the structure may
> > share memory.
> > .SS Ioctls
> > @@ -142,13 +160,17 @@ IFF_ISATAP:Interface is RFC4214 ISATAP interface.
> > .PP
> > Setting the extended (private) interface flags is a privileged operation.
> > .TP
> > -.BR SIOCGIFADDR ", " SIOCSIFADDR
> > -Get or set the address of the device using
> > -.IR ifr_addr .
> > -Setting the interface address is a privileged operation.
> > -For compatibility, only
> > +.BR SIOCGIFADDR ", " SIOCSIFADDR ", " SIOCDIFADDR
> > +Get, set or delete the address of the device using
> > +.IR ifr_addr " or " ifr6_addr " with " ifr6_prefixlen .
>
> Generally, we place each name on a single line.
> The line after .TP is an exception, as you can see above.
> So this would be:
>
> [
> .IR ifr_addr ,
> or
> .I ifr6_addr
> with
> .IR ifr6_prefixlen .
> ]
Ok, I will change it.
> > +Setting or deleting the interface address is a privileged operation.
> > +For compatibility,
> > +.BR SIOCGIFADDR " returns only " AF_INET " addresses, "
> > +.BR SIOCSIFADDR " accepts " AF_INET " and " AF_INET6 " addresses and "
> > +.BR SIOCDIFADDR " deletes only " AF_INET6 " addresses. "
>
> See above.
>
> > .B AF_INET
> > -addresses are accepted or returned.
> > +address can be deleted by setting zero address via
> > +.BR SIOCSIFADDR .
> > .TP
> > .BR SIOCGIFDSTADDR ", " SIOCSIFDSTADDR
> > Get or set the destination address of a point-to-point device using
> >
>
> Thanks,
>
> Alex
>
> --
> Alejandro Colomar
> Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
> http://www.alejandro-colomar.es/
