[Dnsmasq-discuss] [PATCH] Fix parsing of IPv6 addresses with peer from netlink

[Beniamino Galvani]

On Wed, May 18, 2022 at 04:10:52PM +0200, Geert Stappers via Dnsmasq-discuss wrote:
> There new lines and one old line
> > +			if (rta->rta_type == IFA_LOCAL)
> > +			  addrp = ((struct in6_addr *)(rta+1));
> > +			else if (rta->rta_type == IFA_ADDRESS && !addrp)
> >  			  addrp = ((struct in6_addr *)(rta+1)); 
> rewritten as I see them
> +      if (conditionLOCAL)
> +         addrp = value
> +      else if (conditionADDRESS && !addrp)
>           addrp = value
> 
> 
> It is the "&& !addrp" that makes me feel uncomfortable.
> 
> 
> Would
> +      if (conditionLOCAL)
> +         addrp = value
> +      else if (conditionADDRESS)
>           addrp = value
> 
> do?

It wouldn't work, because a netlink message for an address with peer
has:

 IFA_LOCAL   = addr
 IFA_ADDRESS = peer

We would first evaluate IFA_LOCAL and set addrp = addr, then overwrite
it with peer when evaluating the next attribute IFA_ADDRESS.

Since we are interested in 'addr', when IFA_LOCAL is present it should
always override IFA_ADDRESS.

> P.S.
> @Beniamino   welcome to dnsmasq

Thanks,
Beniamino
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