wireguard: allowedips: add WGALLOWEDIP_F_REMOVE_ME flag

The current netlink API for WireGuard does not directly support removal
of allowed ips from a peer. A user can remove an allowed ip from a peer
in one of two ways:

1. By using the WGPEER_F_REPLACE_ALLOWEDIPS flag and providing a new
   list of allowed ips which omits the allowed ip that is to be removed.
2. By reassigning an allowed ip to a "dummy" peer then removing that
   peer with WGPEER_F_REMOVE_ME.

With the first approach, the driver completely rebuilds the allowed ip
list for a peer. If my current configuration is such that a peer has
allowed ips 192.168.0.2 and 192.168.0.3 and I want to remove 192.168.0.2
the actual transition looks like this.

[192.168.0.2, 192.168.0.3] <-- Initial state
[]                         <-- Step 1: Allowed ips removed for peer
[192.168.0.3]              <-- Step 2: Allowed ips added back for peer

This is true even if the allowed ip list is small and the update does
not need to be batched into multiple WG_CMD_SET_DEVICE requests, as the
removal and subsequent addition of ips is non-atomic within a single
request. Consequently, wg_allowedips_lookup_dst and
wg_allowedips_lookup_src may return NULL while reconfiguring a peer even
for packets bound for ips a user did not intend to remove leading to
unintended interruptions in connectivity. This presents in userspace as
failed calls to sendto and sendmsg for UDP sockets. In my case, I ran
netperf while repeatedly reconfiguring the allowed ips for a peer with
wg.

/usr/local/bin/netperf -H 10.102.73.72 -l 10m -t UDP_STREAM -- -R 1 -m 1024
send_data: data send error: No route to host (errno 113)
netperf: send_omni: send_data failed: No route to host

While this may not be of particular concern for environments where peers
and allowed ips are mostly static, systems like Cilium manage peers and
allowed ips in a dynamic environment where peers (i.e. Kubernetes nodes)
and allowed ips (i.e. pods running on those nodes) can frequently
change making WGPEER_F_REPLACE_ALLOWEDIPS problematic.

The second approach avoids any possible connectivity interruptions
but is hacky and less direct, requiring the creation of a temporary
peer just to dispose of an allowed ip.

Introduce a new flag called WGALLOWEDIP_F_REMOVE_ME which in the same
way that WGPEER_F_REMOVE_ME allows a user to remove a single peer from
a WireGuard device's configuration allows a user to remove an ip from a
peer's set of allowed ips. This enables incremental updates to a
device's configuration without any connectivity blips or messy
workarounds.

A corresponding patch for wg extends the existing `wg set` interface to
leverage this feature.

$ wg set wg0 peer <PUBKEY> allowed-ips +192.168.88.0/24,-192.168.0.1/32

When '+' or '-' is prepended to any ip in the list, wg clears
WGPEER_F_REPLACE_ALLOWEDIPS and sets the WGALLOWEDIP_F_REMOVE_ME flag on
any ip prefixed with '-'.

Signed-off-by: Jordan Rife <jordan@jrife.io>
[Jason: minor style nits, fixes to selftest, bump of wireguard-tools version]
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://patch.msgid.link/20250521212707.1767879-5-Jason@zx2c4.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

2 files changed, 30 insertions, 1 deletions

diff --git a/tools/testing/selftests/wireguard/netns.sh b/tools/testing/selftests/wireguard/netns.sh
index 55500f901fbc..a8f550aecb35 100755
--- a/tools/testing/selftests/wireguard/netns.sh
+++ b/tools/testing/selftests/wireguard/netns.sh
@@ -611,6 +611,35 @@ n0 wg set wg0 peer "$pub2" allowed-ips "$allowedips"
 } < <(n0 wg show wg0 allowed-ips)
 ip0 link del wg0
 
+allowedips=( )
+for i in {1..197}; do
+        allowedips+=( 192.168.0.$i )
+        allowedips+=( abcd::$i )
+done
+saved_ifs="$IFS"
+IFS=,
+allowedips="${allowedips[*]}"
+IFS="$saved_ifs"
+ip0 link add wg0 type wireguard
+n0 wg set wg0 peer "$pub1" allowed-ips "$allowedips"
+n0 wg set wg0 peer "$pub1" allowed-ips -192.168.0.1/32,-192.168.0.20/32,-192.168.0.100/32,-abcd::1/128,-abcd::20/128,-abcd::100/128
+{
+	read -r pub allowedips
+	[[ $pub == "$pub1" ]]
+	i=0
+	for ip in $allowedips; do
+		[[ $ip != "192.168.0.1" ]]
+		[[ $ip != "192.168.0.20" ]]
+		[[ $ip != "192.168.0.100" ]]
+		[[ $ip != "abcd::1" ]]
+		[[ $ip != "abcd::20" ]]
+		[[ $ip != "abcd::100" ]]
+		((++i))
+	done
+	((i == 388))
+} < <(n0 wg show wg0 allowed-ips)
+ip0 link del wg0
+
 ! n0 wg show doesnotexist || false
 
 ip0 link add wg0 type wireguard
diff --git a/tools/testing/selftests/wireguard/qemu/Makefile b/tools/testing/selftests/wireguard/qemu/Makefile
index 35856b11c143..f6fbd88914ee 100644
--- a/tools/testing/selftests/wireguard/qemu/Makefile
+++ b/tools/testing/selftests/wireguard/qemu/Makefile
@@ -43,7 +43,7 @@ $(eval $(call tar_download,IPROUTE2,iproute2,5.17.0,.tar.gz,https://www.kernel.o
 $(eval $(call tar_download,IPTABLES,iptables,1.8.7,.tar.bz2,https://www.netfilter.org/projects/iptables/files/,c109c96bb04998cd44156622d36f8e04b140701ec60531a10668cfdff5e8d8f0))
 $(eval $(call tar_download,NMAP,nmap,7.92,.tgz,https://nmap.org/dist/,064183ea642dc4c12b1ab3b5358ce1cef7d2e7e11ffa2849f16d339f5b717117))
 $(eval $(call tar_download,IPUTILS,iputils,s20190709,.tar.gz,https://github.com/iputils/iputils/archive/s20190709.tar.gz/#,a15720dd741d7538dd2645f9f516d193636ae4300ff7dbc8bfca757bf166490a))
-$(eval $(call tar_download,WIREGUARD_TOOLS,wireguard-tools,1.0.20210914,.tar.xz,https://git.zx2c4.com/wireguard-tools/snapshot/,97ff31489217bb265b7ae850d3d0f335ab07d2652ba1feec88b734bc96bd05ac))
+$(eval $(call tar_download,WIREGUARD_TOOLS,wireguard-tools,1.0.20250521,.tar.xz,https://git.zx2c4.com/wireguard-tools/snapshot/,b6f2628b85b1b23cc06517ec9c74f82d52c4cdbd020f3dd2f00c972a1782950e))
 
 export CFLAGS := -O3 -pipe
 ifeq ($(HOST_ARCH),$(ARCH))