From: Amit Cohen Date: Mon, 1 Feb 2021 19:47:52 +0000 (+0200) Subject: net: ipv4: Emit notification when fib hardware flags are changed X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=680aea08e78c003292415518ad270bc20f9c80b1;p=linux.git net: ipv4: Emit notification when fib hardware flags are changed After installing a route to the kernel, user space receives an acknowledgment, which means the route was installed in the kernel, but not necessarily in hardware. The asynchronous nature of route installation in hardware can lead to a routing daemon advertising a route before it was actually installed in hardware. This can result in packet loss or mis-routed packets until the route is installed in hardware. It is also possible for a route already installed in hardware to change its action and therefore its flags. For example, a host route that is trapping packets can be "promoted" to perform decapsulation following the installation of an IPinIP/VXLAN tunnel. Emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/RTM_F_TRAP flags are changed. The aim is to provide an indication to user-space (e.g., routing daemons) about the state of the route in hardware. Introduce a sysctl that controls this behavior. Keep the default value at 0 (i.e., do not emit notifications) for several reasons: - Multiple RTM_NEWROUTE notification per-route might confuse existing routing daemons. - Convergence reasons in routing daemons. - The extra notifications will negatively impact the insertion rate. - Not all users are interested in these notifications. Signed-off-by: Amit Cohen Acked-by: Roopa Prabhu Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski --- diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 2685ec161060b..b0e800e68366f 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -178,6 +178,26 @@ min_adv_mss - INTEGER The advertised MSS depends on the first hop route MTU, but will never be lower than this setting. +fib_notify_on_flag_change - INTEGER + Whether to emit RTM_NEWROUTE notifications whenever RTM_F_OFFLOAD/ + RTM_F_TRAP flags are changed. + + After installing a route to the kernel, user space receives an + acknowledgment, which means the route was installed in the kernel, + but not necessarily in hardware. + It is also possible for a route already installed in hardware to change + its action and therefore its flags. For example, a host route that is + trapping packets can be "promoted" to perform decapsulation following + the installation of an IPinIP/VXLAN tunnel. + The notifications will indicate to user-space the state of the route. + + Default: 0 (Do not emit notifications.) + + Possible values: + + - 0 - Do not emit notifications. + - 1 - Emit notifications. + IP Fragmentation: ipfrag_high_thresh - LONG INTEGER diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 8e4fcac4df72f..70a2a085dd1ae 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -188,6 +188,8 @@ struct netns_ipv4 { int sysctl_udp_wmem_min; int sysctl_udp_rmem_min; + int sysctl_fib_notify_on_flag_change; + #ifdef CONFIG_NET_L3_MASTER_DEV int sysctl_udp_l3mdev_accept; #endif diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index b94fa8eb831bf..ab42f6404fc62 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1871,6 +1871,8 @@ static __net_init int inet_init_net(struct net *net) net->ipv4.sysctl_igmp_llm_reports = 1; net->ipv4.sysctl_igmp_qrv = 2; + net->ipv4.sysctl_fib_notify_on_flag_change = 0; + return 0; } diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 28117c05dc353..60559b7081589 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -1038,6 +1038,8 @@ fib_find_matching_alias(struct net *net, const struct fib_rt_info *fri) void fib_alias_hw_flags_set(struct net *net, const struct fib_rt_info *fri) { struct fib_alias *fa_match; + struct sk_buff *skb; + int err; rcu_read_lock(); @@ -1045,9 +1047,34 @@ void fib_alias_hw_flags_set(struct net *net, const struct fib_rt_info *fri) if (!fa_match) goto out; + if (fa_match->offload == fri->offload && fa_match->trap == fri->trap) + goto out; + fa_match->offload = fri->offload; fa_match->trap = fri->trap; + if (!net->ipv4.sysctl_fib_notify_on_flag_change) + goto out; + + skb = nlmsg_new(fib_nlmsg_size(fa_match->fa_info), GFP_ATOMIC); + if (!skb) { + err = -ENOBUFS; + goto errout; + } + + err = fib_dump_info(skb, 0, 0, RTM_NEWROUTE, fri, 0); + if (err < 0) { + /* -EMSGSIZE implies BUG in fib_nlmsg_size() */ + WARN_ON(err == -EMSGSIZE); + kfree_skb(skb); + goto errout; + } + + rtnl_notify(skb, net, 0, RTNLGRP_IPV4_ROUTE, NULL, GFP_ATOMIC); + goto out; + +errout: + rtnl_set_sk_err(net, RTNLGRP_IPV4_ROUTE, err); out: rcu_read_unlock(); } diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 3e5f4f2e705e8..e5798b3b59d23 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -1354,6 +1354,15 @@ static struct ctl_table ipv4_net_table[] = { .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ONE }, + { + .procname = "fib_notify_on_flag_change", + .data = &init_net.ipv4.sysctl_fib_notify_on_flag_change, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, { } };