Re: [PATCH v2 06/12] icmp: Use -1 to represent "missing" sockets

[David Gibson <david@gibson.dropbear.id.au>]

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On Sat, Jan 06, 2024 at 04:59:32PM +0100, Stefano Brivio wrote:
> On Thu, 21 Dec 2023 17:53:21 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> 
> > icmp_id_map[] contains, amongst other things, fds for "ping" sockets
> > associated with various ICMP echo ids.  However, we only lazily open()
> > those sockets, so many will be missing.  We currently represent that with
> > a 0, which isn't great, since that's technically a valid fd.  Use -1
> > instead.  This does require initializing the fields in icmp_id_map[] but
> > we already have an obvious place to do that.
> > 
> > Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> > ---
> >  icmp.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/icmp.c b/icmp.c
> > index 7a505b4..dd98c7f 100644
> > --- a/icmp.c
> > +++ b/icmp.c
> > @@ -179,7 +179,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  
> >  		iref.id = id = ntohs(ih->un.echo.id);
> >  
> > -		if ((s = icmp_id_map[V4][id].sock) <= 0) {
> > +		if ((s = icmp_id_map[V4][id].sock) < 0) {
> >  			s = sock_l4(c, AF_INET, IPPROTO_ICMP, &c->ip4.addr_out,
> >  				    c->ip4.ifname_out, 0, iref.u32);
> >  			if (s < 0)
> > @@ -221,7 +221,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af,
> >  			return 1;
> >  
> >  		iref.id = id = ntohs(ih->icmp6_identifier);
> > -		if ((s = icmp_id_map[V6][id].sock) <= 0) {
> > +		if ((s = icmp_id_map[V6][id].sock) < 0) {
> >  			s = sock_l4(c, AF_INET6, IPPROTO_ICMPV6,
> >  				    &c->ip6.addr_out,
> >  				    c->ip6.ifname_out, 0, iref.u32);
> > @@ -277,7 +277,7 @@ static void icmp_timer_one(const struct ctx *c, int v6, uint16_t id,
> >  
> >  	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, id_map->sock, NULL);
> >  	close(id_map->sock);
> > -	id_map->sock = 0;
> > +	id_map->sock = -1;
> >  	id_map->seq = -1;
> >  }
> >  
> > @@ -315,6 +315,8 @@ void icmp_init(void)
> >  {
> >  	unsigned i;
> >  
> > -	for (i = 0; i < ICMP_NUM_IDS; i++)
> > +	for (i = 0; i < ICMP_NUM_IDS; i++) {
> >  		icmp_id_map[V4][i].seq = icmp_id_map[V6][i].seq = -1;
> > +		icmp_id_map[V4][i].sock = icmp_id_map[V6][i].sock = -1;
> > +	}
> 
> Another (well, kind of existing) use case for a 0xff-initialising
> helper.

Hm.. it's still not every field, so only sorta.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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