Merge branch 'add-notifications-when-route-hardware-flags-change'

Ido Schimmel says:

====================
Add notifications when route hardware flags change

Routes installed to the kernel can be programmed to capable devices, in
which case they are marked with one of two flags. RTM_F_OFFLOAD for
routes that offload traffic from the kernel and RTM_F_TRAP for routes
that trap packets to the kernel for processing (e.g., host routes).

These flags are of interest to routing daemons since they would like to
delay advertisement of routes until they are installed in hardware. This
allows them to avoid packet loss or misrouted packets. Currently,
routing daemons do not receive any notifications when these flags are
changed, requiring them to poll the kernel tables for changes which is
inefficient.

This series addresses the issue by having the kernel emit RTM_NEWROUTE
notifications whenever these flags change. The behavior is controlled by
two sysctls (net.ipv4.fib_notify_on_flag_change and
net.ipv6.fib_notify_on_flag_change) that default to 0 (no
notifications).

Note that even if route installation in hardware is improved to be more
synchronous, these notifications are still of interest. For example, a
multipath route can change from RTM_F_OFFLOAD to RTM_F_TRAP if its
neighbours become invalid. A routing daemon can choose to withdraw /
replace the route in that case. In addition, the deletion of a route
from the kernel can prompt the installation of an identical route
(already in kernel, with an higher metric) to hardware.

For testing purposes, netdevsim is aligned to simulate a "real" driver
that programs routes to hardware.

Series overview:

Patches #1-#2 align netdevsim to perform route programming in a
non-atomic context

Patches #3-#5 add sysctl to control IPv4 notifications

Patches #6-#8 add sysctl to control IPv6 notifications

Patch #9 extends existing fib tests to set sysctls before running tests

Patch #10 adds test for fib notifications over netdevsim
====================

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

3 files changed, 5 insertions, 7 deletions

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index ac5ff3c3afb1..1e262b23c68b 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -336,13 +336,6 @@ static inline void fib6_info_release(struct fib6_info *f6i)
 		call_rcu(&f6i->rcu, fib6_info_destroy_rcu);
 }
 
-static inline void fib6_info_hw_flags_set(struct fib6_info *f6i, bool offload,
-					  bool trap)
-{
-	f6i->offload = offload;
-	f6i->trap = trap;
-}
-
 enum fib6_walk_state {
 #ifdef CONFIG_IPV6_SUBTREES
 	FWS_S,
@@ -545,6 +538,8 @@ static inline bool fib6_metric_locked(struct fib6_info *f6i, int metric)
 {
 	return !!(f6i->fib6_metrics->metrics[RTAX_LOCK - 1] & (1 << metric));
 }
+void fib6_info_hw_flags_set(struct net *net, struct fib6_info *f6i,
+			    bool offload, bool trap);
 
 #if IS_BUILTIN(CONFIG_IPV6) && defined(CONFIG_BPF_SYSCALL)
 struct bpf_iter__ipv6_route {
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 8e4fcac4df72..70a2a085dd1a 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/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 5ec054473d81..21c0debbd39e 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -51,6 +51,7 @@ struct netns_sysctl_ipv6 {
 	int max_hbh_opts_len;
 	int seg6_flowlabel;
 	bool skip_notify_on_dev_down;
+	int fib_notify_on_flag_change;
 };
 
 struct netns_ipv6 {