* [PATCH] Update Neighbor Cache when IPv6 RA is received on a router @ 2009-08-16 0:19 David Ward 2009-08-16 2:30 ` Mark Smith 2009-08-29 7:04 ` David Miller 0 siblings, 2 replies; 4+ messages in thread From: David Ward @ 2009-08-16 0:19 UTC (permalink / raw) To: netdev; +Cc: David Ward When processing a received IPv6 Router Advertisement, the kernel creates or updates an IPv6 Neighbor Cache entry for the sender -- but presently this does not occur if IPv6 forwarding is enabled (net.ipv6.conf.*.forwarding = 1), or if IPv6 Router Advertisements are not accepted (net.ipv6.conf.*.accept_ra = 0), because in these cases processing of the Router Advertisement has already halted. This patch allows the Neighbor Cache to be updated in these cases, while still avoiding any modification to routes or link parameters. This continues to satisfy RFC 4861, since any entry created in the Neighbor Cache as the result of a received Router Advertisement is still placed in the STALE state. Signed-off-by: David Ward <david.ward@ll•mit.edu> --- net/ipv6/ndisc.c | 14 ++++++++------ 1 files changed, 8 insertions(+), 6 deletions(-) diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c index 1ba42bd..44b4c87 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -1151,10 +1151,6 @@ static void ndisc_router_discovery(struct sk_buff *skb) skb->dev->name); return; } - if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) { - in6_dev_put(in6_dev); - return; - } if (!ndisc_parse_options(opt, optlen, &ndopts)) { in6_dev_put(in6_dev); @@ -1163,6 +1159,10 @@ static void ndisc_router_discovery(struct sk_buff *skb) return; } + /* skip route and link configuration on routers */ + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) + goto skip_linkparms; + #ifdef CONFIG_IPV6_NDISC_NODETYPE /* skip link-specific parameters from interior routers */ if (skb->ndisc_nodetype == NDISC_NODETYPE_NODEFAULT) @@ -1283,9 +1283,7 @@ skip_defrtr: } } -#ifdef CONFIG_IPV6_NDISC_NODETYPE skip_linkparms: -#endif /* * Process options. @@ -1312,6 +1310,10 @@ skip_linkparms: NEIGH_UPDATE_F_ISROUTER); } + /* skip route and link configuration on routers */ + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) + goto out; + #ifdef CONFIG_IPV6_ROUTE_INFO if (in6_dev->cnf.accept_ra_rtr_pref && ndopts.nd_opts_ri) { struct nd_opt_hdr *p; -- 1.6.0.4 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] Update Neighbor Cache when IPv6 RA is received on a router 2009-08-16 0:19 [PATCH] Update Neighbor Cache when IPv6 RA is received on a router David Ward @ 2009-08-16 2:30 ` Mark Smith 2009-08-16 5:47 ` David Ward 2009-08-29 7:04 ` David Miller 1 sibling, 1 reply; 4+ messages in thread From: Mark Smith @ 2009-08-16 2:30 UTC (permalink / raw) To: David Ward; +Cc: netdev Hi David, On Sat, 15 Aug 2009 20:19:54 -0400 David Ward <david.ward@ll•mit.edu> wrote: > When processing a received IPv6 Router Advertisement, the kernel > creates or updates an IPv6 Neighbor Cache entry for the sender -- > but presently this does not occur if IPv6 forwarding is enabled > (net.ipv6.conf.*.forwarding = 1), or if IPv6 Router Advertisements > are not accepted (net.ipv6.conf.*.accept_ra = 0), because in these > cases processing of the Router Advertisement has already halted. > > This patch allows the Neighbor Cache to be updated in these cases, > while still avoiding any modification to routes or link parameters. > I'm a bit confused what benefit this has. Is the intent to avoid a Neighbor Solicitation being triggered when a recent RA has already provided the router's link local address, therefore reducing by a small mount ND traffic? > This continues to satisfy RFC 4861, since any entry created in the > Neighbor Cache as the result of a received Router Advertisement is > still placed in the STALE state. > > Signed-off-by: David Ward <david.ward@ll•mit.edu> > --- > net/ipv6/ndisc.c | 14 ++++++++------ > 1 files changed, 8 insertions(+), 6 deletions(-) > > diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c > index 1ba42bd..44b4c87 100644 > --- a/net/ipv6/ndisc.c > +++ b/net/ipv6/ndisc.c > @@ -1151,10 +1151,6 @@ static void ndisc_router_discovery(struct sk_buff *skb) > skb->dev->name); > return; > } > - if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) { > - in6_dev_put(in6_dev); > - return; > - } > > if (!ndisc_parse_options(opt, optlen, &ndopts)) { > in6_dev_put(in6_dev); > @@ -1163,6 +1159,10 @@ static void ndisc_router_discovery(struct sk_buff *skb) > return; > } > > + /* skip route and link configuration on routers */ > + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) > + goto skip_linkparms; > + > #ifdef CONFIG_IPV6_NDISC_NODETYPE > /* skip link-specific parameters from interior routers */ > if (skb->ndisc_nodetype == NDISC_NODETYPE_NODEFAULT) > @@ -1283,9 +1283,7 @@ skip_defrtr: > } > } > > -#ifdef CONFIG_IPV6_NDISC_NODETYPE > skip_linkparms: > -#endif > > /* > * Process options. > @@ -1312,6 +1310,10 @@ skip_linkparms: > NEIGH_UPDATE_F_ISROUTER); > } > > + /* skip route and link configuration on routers */ > + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) > + goto out; > + > #ifdef CONFIG_IPV6_ROUTE_INFO > if (in6_dev->cnf.accept_ra_rtr_pref && ndopts.nd_opts_ri) { > struct nd_opt_hdr *p; > -- > 1.6.0.4 > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger•kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Update Neighbor Cache when IPv6 RA is received on a router 2009-08-16 2:30 ` Mark Smith @ 2009-08-16 5:47 ` David Ward 0 siblings, 0 replies; 4+ messages in thread From: David Ward @ 2009-08-16 5:47 UTC (permalink / raw) To: Mark Smith; +Cc: netdev Mark, thank you very much for your response. On 08/15/2009 10:30 PM, Mark Smith wrote: > Hi David, > > On Sat, 15 Aug 2009 20:19:54 -0400 > David Ward <david.ward@ll•mit.edu> wrote: > >> When processing a received IPv6 Router Advertisement, the kernel >> creates or updates an IPv6 Neighbor Cache entry for the sender -- >> but presently this does not occur if IPv6 forwarding is enabled >> (net.ipv6.conf.*.forwarding = 1), or if IPv6 Router Advertisements >> are not accepted (net.ipv6.conf.*.accept_ra = 0), because in these >> cases processing of the Router Advertisement has already halted. >> >> This patch allows the Neighbor Cache to be updated in these cases, >> while still avoiding any modification to routes or link parameters. >> > > I'm a bit confused what benefit this has. I apologize for not making that clear. It allows routers to utilize the Neighbor Cache to keep track of neighboring routers, which are learned about through the periodic Router Advertisements. By doing so, applications communicating through upper layers can make use of the Neighbor Cache, for example, as a basis for initiating dynamic peering between neighboring routers. Non-routers are already able to keep track of their neighboring routers in the Neighbor Cache; this simply allows routers to do the same. This cannot be achieved through Neighbor Advertisements, because they are usually sent in response to a direct Neighbor Solicitation, while Router Advertisements are periodically multicast to the all-nodes group. > Is the intent to avoid a Neighbor Solicitation being triggered when a > recent RA has already provided the router's link local address, > therefore reducing by a small mount ND traffic? No. This patch does not preclude the need to send a Neighbor Solicitation to another router to determine reachability. That would violate RFC 4861, which states that a Router Advertisement "MUST NOT be treated as a reachability confirmation". In the dynamic router peering scenario, the Neighbor Cache entry could be used to learn that the neighboring router exists and is a potential peer -- but reachability must still be determined before a peering session could actually be attempted. >> This continues to satisfy RFC 4861, since any entry created in the >> Neighbor Cache as the result of a received Router Advertisement is >> still placed in the STALE state. >> >> Signed-off-by: David Ward <david.ward@ll•mit.edu> >> --- >> net/ipv6/ndisc.c | 14 ++++++++------ >> 1 files changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c >> index 1ba42bd..44b4c87 100644 >> --- a/net/ipv6/ndisc.c >> +++ b/net/ipv6/ndisc.c >> @@ -1151,10 +1151,6 @@ static void ndisc_router_discovery(struct >> sk_buff *skb) >> skb->dev->name); >> return; >> } >> - if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) { >> - in6_dev_put(in6_dev); >> - return; >> - } >> >> if (!ndisc_parse_options(opt, optlen, &ndopts)) { >> in6_dev_put(in6_dev); >> @@ -1163,6 +1159,10 @@ static void ndisc_router_discovery(struct >> sk_buff *skb) >> return; >> } >> >> + /* skip route and link configuration on routers */ >> + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) >> + goto skip_linkparms; >> + >> #ifdef CONFIG_IPV6_NDISC_NODETYPE >> /* skip link-specific parameters from interior routers */ >> if (skb->ndisc_nodetype == NDISC_NODETYPE_NODEFAULT) >> @@ -1283,9 +1283,7 @@ skip_defrtr: >> } >> } >> >> -#ifdef CONFIG_IPV6_NDISC_NODETYPE >> skip_linkparms: >> -#endif >> >> /* >> * Process options. >> @@ -1312,6 +1310,10 @@ skip_linkparms: >> NEIGH_UPDATE_F_ISROUTER); >> } >> >> + /* skip route and link configuration on routers */ >> + if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_ra) >> + goto out; >> + >> #ifdef CONFIG_IPV6_ROUTE_INFO >> if (in6_dev->cnf.accept_ra_rtr_pref && ndopts.nd_opts_ri) { >> struct nd_opt_hdr *p; >> -- >> 1.6.0.4 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Update Neighbor Cache when IPv6 RA is received on a router 2009-08-16 0:19 [PATCH] Update Neighbor Cache when IPv6 RA is received on a router David Ward 2009-08-16 2:30 ` Mark Smith @ 2009-08-29 7:04 ` David Miller 1 sibling, 0 replies; 4+ messages in thread From: David Miller @ 2009-08-29 7:04 UTC (permalink / raw) To: david.ward; +Cc: netdev From: David Ward <david.ward@ll•mit.edu> Date: Sat, 15 Aug 2009 20:19:54 -0400 > When processing a received IPv6 Router Advertisement, the kernel > creates or updates an IPv6 Neighbor Cache entry for the sender -- > but presently this does not occur if IPv6 forwarding is enabled > (net.ipv6.conf.*.forwarding = 1), or if IPv6 Router Advertisements > are not accepted (net.ipv6.conf.*.accept_ra = 0), because in these > cases processing of the Router Advertisement has already halted. > > This patch allows the Neighbor Cache to be updated in these cases, > while still avoiding any modification to routes or link parameters. > > This continues to satisfy RFC 4861, since any entry created in the > Neighbor Cache as the result of a received Router Advertisement is > still placed in the STALE state. > > Signed-off-by: David Ward <david.ward@ll•mit.edu> This seems OK, applied to net-next-2.6 Thanks. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2009-08-29 7:04 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2009-08-16 0:19 [PATCH] Update Neighbor Cache when IPv6 RA is received on a router David Ward 2009-08-16 2:30 ` Mark Smith 2009-08-16 5:47 ` David Ward 2009-08-29 7:04 ` David Miller
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