[PATCH] rpc: 'getaddrinfo' function support both IPv4 and IPv6

[Daniel P. Berrangé]

On Mon, Mar 02, 2020 at 05:54:42PM +0100, Ján Tomko wrote:
> The commit summary is too generic.
> How about:
> rpc: getaddrinfo: also accept IPv4-mapped IPv6 addresses
> 
> On a Monday in 2020, Zhimin Feng wrote:
> > If only IPv6 is configured and nscd is started, getaddrinfo
> 
> Is ncsd required to reproduce this?
> 
> Looking at glibc source:
> libvirt passes AI_ADDRCONFIG and if getifaddrs returs only one family,
> it is placed into req->ai_family and the code below is hit.
> 
> > function reture value is -9. So hints.ai_flags should include
> > the AI_V4MAPPED flag.
> > 
> > The following is the partial implementation of getaddrinfo(glibc):
> > 
> >    if (req->ai_family == AF_UNSPEC || req->ai_family == AF_INET)
> >        at->family = AF_INET;
> >    else if (req->ai_family == AF_INET6 && (req->ai_flags & AI_V4MAPPED))
> >    {
> >        at->addr[3] = at->addr[0];
> > 	at->addr[2] = htonl (0xffff);
> > 	at->addr[1] = 0;
> > 	at->addr[0] = 0;
> > 	at->family = AF_INET6;
> >    }
> >    else
> >    {
> >         result = -EAI_ADDRFAMILY;
> >         goto free_and_return;
> >    }
> 
> However small, I'd rather not include GPL code in our commit messages.
> Proposed commit message:
> 
> If only IPv6 is configured on the host, getaddrinfo with AI_ADDRCONFIG
> in hints would return EAI_ADDRFAMILY for nodenames that resolve to IPv4.
> 
> Also pass AI_V4MAPPED to accept IPv4-mapped addresses on IPv6-only
> systems.
> 
> > 
> > Signed-off-by: Zhimin Feng <fengzhimin1 at huawei.com>
> > ---
> > src/rpc/virnetsocket.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/src/rpc/virnetsocket.c b/src/rpc/virnetsocket.c
> > index a217404fa6..c547acefc0 100644
> > --- a/src/rpc/virnetsocket.c
> > +++ b/src/rpc/virnetsocket.c
> > @@ -575,7 +575,7 @@ int virNetSocketNewConnectTCP(const char *nodename,
> > 
> >     memset(&hints, 0, sizeof(hints));
> >     hints.ai_family = family;
> > -    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
> > +    hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG | AI_V4MAPPED;
> >     hints.ai_socktype = SOCK_STREAM;
> > 
> >     int e = getaddrinfo(nodename, service, &hints, &ai);
> 
> Reviewed-by: Ján Tomko <jtomko at redhat.com>

I noticed that glibc man pages say if ai_flags is 0, then it defaults
to AI_ADDRCONFIG | AI_V4MAPPED.  Libvirt had to set ai_flags to get the
AI_PASSIVE flag, and so given that adding AI_V4MAPPED makes sense to
regain the default behaviour we're loosing.

Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>


Regards,
Daniel
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