[PATCH 2/3 net-next v5] ipv4: handle devconf post-set actions on netlink updates
From: Fernando Fernandez Mancera <hidden>
Date: 2026-06-07 11:01:48
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
When IPv4 device configuration parameters are updated via netlink, the kernel currently only updates the value. This bypasses several post-modification actions that occur when these same parameters are updated via sysctl, such as flushing the routing cache or emitting RTM_NEWNETCONF notifications. This patch addresses the inconsistency by calling the devinet_conf_post_set() helper inside inet_set_link_af(). If a flush is required, we defer it until the netlink attribute parsing loop completes. This ensures consistent behavior and side-effects for devconf changes, regardless of whether they are initiated via sysctl or netlink. Reviewed-by: Nicolas Dichtel <redacted> Signed-off-by: Fernando Fernandez Mancera <redacted> --- v2: handled forwarding notification and disabling LRO v3: no changes v4: no changes v5: no changes --- net/ipv4/devinet.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 8300516fb38f..a35b72662e43 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c@@ -2161,6 +2161,20 @@ static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf, NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN, ifindex, cnf); break; + case IPV4_DEVCONF_FORWARDING: + if (new == 1) { + /* it is safe to use container_of() because forwarding case + * is only used by the netlink path + */ + struct in_device *idev = container_of(cnf, struct in_device, cnf); + + netif_disable_lro(idev->dev); + } + + inet_netconf_notify_devconf(net, RTM_NEWNETCONF, + NETCONFA_FORWARDING, + ifindex, cnf); + return true; default: break; }
@@ -2173,6 +2187,8 @@ static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla, { struct in_device *in_dev = __in_dev_get_rtnl(dev); struct nlattr *a, *tb[IFLA_INET_MAX+1]; + struct net *net = dev_net(dev); + bool flush_cache = false; int rem; if (!in_dev)
@@ -2182,8 +2198,17 @@ static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla, return -EINVAL; if (tb[IFLA_INET_CONF]) { - nla_for_each_nested(a, tb[IFLA_INET_CONF], rem) - ipv4_devconf_set(in_dev, nla_type(a), nla_get_u32(a)); + nla_for_each_nested(a, tb[IFLA_INET_CONF], rem) { + int old_value = ipv4_devconf_get(in_dev, nla_type(a)); + int new_value = nla_get_u32(a); + + ipv4_devconf_set(in_dev, nla_type(a), new_value); + if (devinet_conf_post_set(net, &in_dev->cnf, nla_type(a), new_value, + old_value, dev->ifindex)) + flush_cache = true; + } + if (flush_cache) + rt_cache_flush(net); } return 0;
--
2.54.0