Re: [PATCH net-next v3 1/5] net/ipv6: set expires in rt6_add_dflt_router().

[Hangbin Liu <liuhangbin@gmail.com>]

On Fri, Feb 02, 2024 at 12:21:56AM -0800, thinker.li@gmail.com wrote:
> From: Kui-Feng Lee <thinker.li@gmail.com>
> 
> Pass the duration of a lifetime (in seconds) to the function
> rt6_add_dflt_router() so that it can properly set the expiration time.
> 
> The function ndisc_router_discovery() is the only one that calls
> rt6_add_dflt_router(), and it will later set the expiration time for the
> route created by rt6_add_dflt_router(). However, there is a gap of time
> between calling rt6_add_dflt_router() and setting the expiration time in
> ndisc_router_discovery(). During this period, there is a possibility that a
> new route may be removed from the routing table. By setting the correct
> expiration time in rt6_add_dflt_router(), we can prevent this from
> happening. The reason for setting RTF_EXPIRES in rt6_add_dflt_router() is
> to start the Garbage Collection (GC) timer, as it only activates when a
> route with RTF_EXPIRES is added to a table.
> 
> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
> ---
>  include/net/ip6_route.h | 3 ++-
>  net/ipv6/ndisc.c        | 3 ++-
>  net/ipv6/route.c        | 4 +++-
>  3 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
> index 28b065790261..52a51c69aa9d 100644
> --- a/include/net/ip6_route.h
> +++ b/include/net/ip6_route.h
> @@ -170,7 +170,8 @@ struct fib6_info *rt6_get_dflt_router(struct net *net,
>  struct fib6_info *rt6_add_dflt_router(struct net *net,
>  				     const struct in6_addr *gwaddr,
>  				     struct net_device *dev, unsigned int pref,
> -				     u32 defrtr_usr_metric);
> +				     u32 defrtr_usr_metric,
> +				     int lifetime);
>  
>  void rt6_purge_dflt_routers(struct net *net);
>  
> diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
> index a19999b30bc0..a68462668158 100644
> --- a/net/ipv6/ndisc.c
> +++ b/net/ipv6/ndisc.c
> @@ -1382,7 +1382,8 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
>  			neigh_release(neigh);
>  
>  		rt = rt6_add_dflt_router(net, &ipv6_hdr(skb)->saddr,
> -					 skb->dev, pref, defrtr_usr_metric);
> +					 skb->dev, pref, defrtr_usr_metric,
> +					 lifetime);
>  		if (!rt) {
>  			ND_PRINTK(0, err,
>  				  "RA: %s failed to add default route\n",
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 63b4c6056582..98abba8f15cd 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -4355,7 +4355,8 @@ struct fib6_info *rt6_add_dflt_router(struct net *net,
>  				     const struct in6_addr *gwaddr,
>  				     struct net_device *dev,
>  				     unsigned int pref,
> -				     u32 defrtr_usr_metric)
> +				     u32 defrtr_usr_metric,
> +				     int lifetime)
>  {
>  	struct fib6_config cfg = {
>  		.fc_table	= l3mdev_fib_table(dev) ? : RT6_TABLE_DFLT,
> @@ -4368,6 +4369,7 @@ struct fib6_info *rt6_add_dflt_router(struct net *net,
>  		.fc_nlinfo.portid = 0,
>  		.fc_nlinfo.nlh = NULL,
>  		.fc_nlinfo.nl_net = net,
> +		.fc_expires = jiffies_to_clock_t(lifetime * HZ),
>  	};
>  
>  	cfg.fc_gateway = *gwaddr;
> -- 
> 2.34.1
> 

Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>