On 05/25/2017 10:42 AM, Roopa Prabhu wrote:
> From: David Ahern <dsah...@gmail.com>
>
> Convert inet_rtm_getroute to use ip_route_input_rcu and
> ip_route_output_key_hash_rcu passing the fib_result arg to both.
> The rcu lock is held through the creation of the response, so the
> rtable/dst does not need to be attached to the skb and is passed
> to rt_fill_info directly.
>
> In converting from ip_route_output_key to ip_route_output_key_hash_rcu
> the xfrm_lookup_route in ip_route_output_flow is dropped since
> flowi4_proto is not set for a route get request.
>
> Signed-off-by: David Ahern <dsah...@gmail.com>
> Signed-off-by: Roopa Prabhu <ro...@cumulusnetworks.com>
> ---
Hi Roopa, David,
I'm getting a usage count bug with this patch,
unregister_netdevice: waiting for lo to become free. Usage count = 1
see below,
> net/ipv4/route.c | 21 +++++++++++++--------
> 1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index d8fcecc..1fa9127 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2534,11 +2534,11 @@ struct rtable *ip_route_output_flow(struct net *net,
> struct flowi4 *flp4,
> }
> EXPORT_SYMBOL_GPL(ip_route_output_flow);
>
> +/* called with rcu_read_lock held */
> static int rt_fill_info(struct net *net, __be32 dst, __be32 src, u32
> table_id,
> struct flowi4 *fl4, struct sk_buff *skb, u32 portid,
> - u32 seq)
> + u32 seq, struct rtable *rt)
> {
> - struct rtable *rt = skb_rtable(skb);
> struct rtmsg *r;
> struct nlmsghdr *nlh;
> unsigned long expires = 0;
> @@ -2653,6 +2653,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
> struct nlmsghdr *nlh,
> struct net *net = sock_net(in_skb->sk);
> struct rtmsg *rtm;
> struct nlattr *tb[RTA_MAX+1];
> + struct fib_result res = {};
> struct rtable *rt = NULL;
> struct flowi4 fl4;
> __be32 dst = 0;
> @@ -2709,10 +2710,12 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
> struct nlmsghdr *nlh,
> fl4.flowi4_mark = mark;
> fl4.flowi4_uid = uid;
>
> + rcu_read_lock();
> +
> if (iif) {
> struct net_device *dev;
>
> - dev = __dev_get_by_index(net, iif);
> + dev = dev_get_by_index_rcu(net, iif);
> if (!dev) {
> err = -ENODEV;
> goto errout_free;
> @@ -2721,14 +2724,14 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
> struct nlmsghdr *nlh,
> skb->protocol = htons(ETH_P_IP);
> skb->dev = dev;
> skb->mark = mark;
> - err = ip_route_input(skb, dst, src, rtm->rtm_tos, dev);
> + err = ip_route_input_rcu(skb, dst, src, rtm->rtm_tos,
> + dev, &res);
>
> rt = skb_rtable(skb);
> if (err == 0 && rt->dst.error)
> err = -rt->dst.error;
> } else {
> - rt = ip_route_output_key(net, &fl4);
> -
> + rt = ip_route_output_key_hash_rcu(net, &fl4, &res, skb);
> err = 0;
> if (IS_ERR(rt))
> err = PTR_ERR(rt);
> @@ -2737,7 +2740,6 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
> struct nlmsghdr *nlh,
> if (err)
> goto errout_free;
>
> - skb_dst_set(skb, &rt->dst);
Why did you remove this? Neither ip_route_input() or ip_route_output_key()
seem to justify this with a quick scan on my side. Feel free to correct me
here.
The following fix resolves my issues,
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f1f2e5a..8f373bd 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2750,6 +2750,7 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
struct nlmsghdr *nlh,
if (err)
goto errout_free;
+ skb_dst_set(skb, &rt->dst);
if (rtm->rtm_flags & RTM_F_NOTIFY)
rt->rt_flags |= RTCF_NOTIFY;
Thanks,
John
> if (rtm->rtm_flags & RTM_F_NOTIFY)
> rt->rt_flags |= RTCF_NOTIFY;
>
> @@ -2745,15 +2747,18 @@ static int inet_rtm_getroute(struct sk_buff *in_skb,
> struct nlmsghdr *nlh,
> table_id = rt->rt_table_id;
>
> err = rt_fill_info(net, dst, src, table_id, &fl4, skb,
> - NETLINK_CB(in_skb).portid, nlh->nlmsg_seq);
> + NETLINK_CB(in_skb).portid, nlh->nlmsg_seq, rt);
> if (err < 0)
> goto errout_free;
>
> + rcu_read_unlock();
> +
> err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
> errout:
> return err;
>
> errout_free:
> + rcu_read_unlock();
> kfree_skb(skb);
> goto errout;
> }
>
