From dc10633ca2bb951c6fbb362c18eb7eff0bfbdf97 Mon Sep 17 00:00:00 2001 From: Amit Cohen Date: Mon, 1 Feb 2021 21:47:52 +0200 Subject: [PATCH] UPSTREAM: 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. Change-Id: I3fb0d92d503281be8efd5dc46b87db04d10c5989 Signed-off-by: Amit Cohen Acked-by: Roopa Prabhu Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Signed-off-by: Jakub Kicinski --- Documentation/networking/ip-sysctl.txt | 20 +++++++++++++++++++ include/net/netns/ipv4.h | 2 ++ net/ipv4/af_inet.c | 2 ++ net/ipv4/fib_trie.c | 27 ++++++++++++++++++++++++++ net/ipv4/sysctl_net_ipv4.c | 9 +++++++++ 5 files changed, 60 insertions(+) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 51d0f41d4295..56e295e086e9 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -141,6 +141,26 @@ 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 efff08633df8..63f01603d315 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -180,6 +180,8 @@ 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 e329b820f29e..f0276286825c 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1833,6 +1833,8 @@ 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 d9f496c4aa81..0fe6a536106a 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -1040,6 +1040,8 @@ 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(); @@ -1047,9 +1049,34 @@ 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 0da8f52f4036..b8f06fd755f1 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -1214,6 +1214,15 @@ static struct ctl_table ipv4_net_table[] = { .proc_handler = proc_dointvec_minmax, .extra1 = &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 = &zero, + .extra2 = &one, + }, { } };