* [PATCH 1/2 net-next] ipv4: centralize devconf sysctl handling
@ 2026-03-25 16:10 Fernando Fernandez Mancera
2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
0 siblings, 1 reply; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-25 16:10 UTC (permalink / raw)
To: netdev
Cc: horms, pabeni, kuba, edumazet, dsahern, davem,
Fernando Fernandez Mancera
The logic for handling IPv4 devconf sysctls is scattered. Notification
and cache flushes are managed in devinet_conf_proc(), while a separate
ipv4_doint_and_flush() function and DEVINET_SYSCTL_FLUSHING_ENTRY macro
is used for properties that solely require a cache flush.
This patch refactors the sysctl handling by introducing a centralized
helper, devinet_conf_post_set(). This new function evaluates the changed
attribute and handles all necessary operations like triggering netlink
notifications. It returns a boolean indicating whether a routing cache
flush is required.
Note that the boolean is necessary as this function will be re-used for
netlink IPv4 devconf handling where the cache flushing must wait until
all the attributes have been processed.
Finally, this is introducing a small change in behavior for
IPV4_DEVCONF_ROUTE_LOCALNET. As commit d0daebc3d622 ("ipv4: Add
interface option to enable routing of 127.0.0.0/8") intended, the cache
flush should only be performed when ROUTE_LOCALNET changes from 1 to 0.
Unfortunately, this was not true because while implementing it the
DEVINET_SYSCTL_FLUSHING_ENTRY was used for the attribute, making the
code related to it on devinet_conf_proc() dead.
IPV4_DEVCONF_FORWARDING is still being handled separately as it requires
more operations.
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
Note: I ripped of the previous version tag because the patch is now
something completely different given the rework of devconf sysctl
handling
---
net/ipv4/devinet.c | 127 ++++++++++++++++++++++++---------------------
1 file changed, 68 insertions(+), 59 deletions(-)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 58fe7cb69545..c81bb948d59f 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2500,6 +2500,46 @@ static int devinet_conf_ifindex(struct net *net, struct ipv4_devconf *cnf)
}
}
+static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
+ int attr, int new, int old, int ifindex)
+{
+ if (new == old)
+ return false;
+
+ switch (attr) {
+ case IPV4_DEVCONF_ROUTE_LOCALNET:
+ case IPV4_DEVCONF_ACCEPT_LOCAL:
+ if (new == 0)
+ return true;
+ break;
+ case IPV4_DEVCONF_NOXFRM:
+ case IPV4_DEVCONF_NOPOLICY:
+ case IPV4_DEVCONF_PROMOTE_SECONDARIES:
+ case IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST:
+ case IPV4_DEVCONF_BC_FORWARDING:
+ return true;
+ case IPV4_DEVCONF_RP_FILTER:
+ inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
+ NETCONFA_RP_FILTER,
+ ifindex, cnf);
+ break;
+ case IPV4_DEVCONF_PROXY_ARP:
+ inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
+ NETCONFA_PROXY_NEIGH,
+ ifindex, cnf);
+ break;
+ case IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN:
+ inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
+ NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
+ ifindex, cnf);
+ break;
+ default:
+ break;
+ }
+
+ return false;
+}
+
static int devinet_conf_proc(const struct ctl_table *ctl, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
@@ -2509,44 +2549,31 @@ static int devinet_conf_proc(const struct ctl_table *ctl, int write,
if (write) {
struct ipv4_devconf *cnf = ctl->extra1;
- struct net *net = ctl->extra2;
int i = (int *)ctl->data - cnf->data;
+ struct net *net = ctl->extra2;
int ifindex;
- set_bit(i, cnf->state);
-
- if (cnf == net->ipv4.devconf_dflt)
- devinet_copy_dflt_conf(net, i);
- if (i == IPV4_DEVCONF_ACCEPT_LOCAL - 1 ||
- i == IPV4_DEVCONF_ROUTE_LOCALNET - 1)
- if ((new_value == 0) && (old_value != 0))
- rt_cache_flush(net);
+ /* These attributes are bypassing the tracking state,
+ * for the rest track the state and propagate the changes
+ * to default config
+ */
+ switch (i + 1) {
+ case IPV4_DEVCONF_NOXFRM:
+ case IPV4_DEVCONF_NOPOLICY:
+ case IPV4_DEVCONF_PROMOTE_SECONDARIES:
+ case IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST:
+ break;
+ default:
+ set_bit(i, cnf->state);
+ if (cnf == net->ipv4.devconf_dflt)
+ devinet_copy_dflt_conf(net, i);
+ break;
+ }
- if (i == IPV4_DEVCONF_BC_FORWARDING - 1 &&
- new_value != old_value)
+ ifindex = devinet_conf_ifindex(net, cnf);
+ if (devinet_conf_post_set(net, cnf, i + 1, new_value,
+ old_value, ifindex))
rt_cache_flush(net);
-
- if (i == IPV4_DEVCONF_RP_FILTER - 1 &&
- new_value != old_value) {
- ifindex = devinet_conf_ifindex(net, cnf);
- inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
- NETCONFA_RP_FILTER,
- ifindex, cnf);
- }
- if (i == IPV4_DEVCONF_PROXY_ARP - 1 &&
- new_value != old_value) {
- ifindex = devinet_conf_ifindex(net, cnf);
- inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
- NETCONFA_PROXY_NEIGH,
- ifindex, cnf);
- }
- if (i == IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN - 1 &&
- new_value != old_value) {
- ifindex = devinet_conf_ifindex(net, cnf);
- inet_netconf_notify_devconf(net, RTM_NEWNETCONF,
- NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
- ifindex, cnf);
- }
}
return ret;
@@ -2599,20 +2626,6 @@ static int devinet_sysctl_forward(const struct ctl_table *ctl, int write,
return ret;
}
-static int ipv4_doint_and_flush(const struct ctl_table *ctl, int write,
- void *buffer, size_t *lenp, loff_t *ppos)
-{
- int *valp = ctl->data;
- int val = *valp;
- int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
- struct net *net = ctl->extra2;
-
- if (write && *valp != val)
- rt_cache_flush(net);
-
- return ret;
-}
-
#define DEVINET_SYSCTL_ENTRY(attr, name, mval, proc) \
{ \
.procname = name, \
@@ -2633,9 +2646,6 @@ static int ipv4_doint_and_flush(const struct ctl_table *ctl, int write,
#define DEVINET_SYSCTL_COMPLEX_ENTRY(attr, name, proc) \
DEVINET_SYSCTL_ENTRY(attr, name, 0644, proc)
-#define DEVINET_SYSCTL_FLUSHING_ENTRY(attr, name) \
- DEVINET_SYSCTL_COMPLEX_ENTRY(attr, name, ipv4_doint_and_flush)
-
static struct devinet_sysctl_table {
struct ctl_table_header *sysctl_header;
struct ctl_table devinet_vars[IPV4_DEVCONF_MAX];
@@ -2678,15 +2688,14 @@ static struct devinet_sysctl_table {
"ignore_routes_with_linkdown"),
DEVINET_SYSCTL_RW_ENTRY(DROP_GRATUITOUS_ARP,
"drop_gratuitous_arp"),
-
- DEVINET_SYSCTL_FLUSHING_ENTRY(NOXFRM, "disable_xfrm"),
- DEVINET_SYSCTL_FLUSHING_ENTRY(NOPOLICY, "disable_policy"),
- DEVINET_SYSCTL_FLUSHING_ENTRY(PROMOTE_SECONDARIES,
- "promote_secondaries"),
- DEVINET_SYSCTL_FLUSHING_ENTRY(ROUTE_LOCALNET,
- "route_localnet"),
- DEVINET_SYSCTL_FLUSHING_ENTRY(DROP_UNICAST_IN_L2_MULTICAST,
- "drop_unicast_in_l2_multicast"),
+ DEVINET_SYSCTL_RW_ENTRY(NOXFRM, "disable_xfrm"),
+ DEVINET_SYSCTL_RW_ENTRY(NOPOLICY, "disable_policy"),
+ DEVINET_SYSCTL_RW_ENTRY(PROMOTE_SECONDARIES,
+ "promote_secondaries"),
+ DEVINET_SYSCTL_RW_ENTRY(ROUTE_LOCALNET,
+ "route_localnet"),
+ DEVINET_SYSCTL_RW_ENTRY(DROP_UNICAST_IN_L2_MULTICAST,
+ "drop_unicast_in_l2_multicast"),
},
};
--
2.53.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
2026-03-25 16:10 [PATCH 1/2 net-next] ipv4: centralize devconf sysctl handling Fernando Fernandez Mancera
@ 2026-03-25 16:10 ` Fernando Fernandez Mancera
2026-03-25 20:39 ` Fernando Fernandez Mancera
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-25 16:10 UTC (permalink / raw)
To: netdev
Cc: horms, pabeni, kuba, edumazet, dsahern, davem,
Fernando Fernandez Mancera
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.
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
net/ipv4/devinet.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index c81bb948d59f..555f85139fb5 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -2128,11 +2128,16 @@ static int inet_validate_link_af(const struct net_device *dev,
return 0;
}
+static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
+ int attr, int new, int old, int index);
+
static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla,
struct netlink_ext_ack *extack)
{
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)
@@ -2142,8 +2147,17 @@ 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;
@@ -2507,6 +2521,10 @@ static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
return false;
switch (attr) {
+ case IPV4_DEVCONF_FORWARDING:
+ if (new == 1)
+ return true;
+ break;
case IPV4_DEVCONF_ROUTE_LOCALNET:
case IPV4_DEVCONF_ACCEPT_LOCAL:
if (new == 0)
--
2.53.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
@ 2026-03-25 20:39 ` Fernando Fernandez Mancera
2026-03-26 3:39 ` kernel test robot
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Fernando Fernandez Mancera @ 2026-03-25 20:39 UTC (permalink / raw)
To: netdev; +Cc: horms, pabeni, kuba, edumazet, dsahern, davem
On 3/25/26 5:10 PM, Fernando Fernandez Mancera wrote:
> 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.
>
> Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
> ---
> net/ipv4/devinet.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
[...]
> @@ -2507,6 +2521,10 @@ static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
> return false;
>
> switch (attr) {
> + case IPV4_DEVCONF_FORWARDING:
> + if (new == 1)
> + return true;
> + break;
This is missing disabling LRO and also the proper netlink notification.
I will fix that on a V2. *facepalm* it does not matter how much I
reviewed this, I missed that detail, sorry.
> case IPV4_DEVCONF_ROUTE_LOCALNET:
> case IPV4_DEVCONF_ACCEPT_LOCAL:
> if (new == 0)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
2026-03-25 20:39 ` Fernando Fernandez Mancera
@ 2026-03-26 3:39 ` kernel test robot
2026-03-26 7:25 ` kernel test robot
2026-03-26 12:08 ` kernel test robot
3 siblings, 0 replies; 6+ messages in thread
From: kernel test robot @ 2026-03-26 3:39 UTC (permalink / raw)
To: Fernando Fernandez Mancera, netdev
Cc: oe-kbuild-all, horms, pabeni, kuba, edumazet, dsahern, davem,
Fernando Fernandez Mancera
Hi Fernando,
kernel test robot noticed the following build warnings:
[auto build test WARNING on net-next/main]
url: https://github.com/intel-lab-lkp/linux/commits/Fernando-Fernandez-Mancera/ipv4-ipv4-handle-devconf-post-set-actions-on-netlink-updates/20260326-020953
base: net-next/main
patch link: https://lore.kernel.org/r/20260325161020.3516-2-fmancera%40suse.de
patch subject: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
config: arm-randconfig-002-20260326 (https://download.01.org/0day-ci/archive/20260326/202603261127.QrC9E9f0-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260326/202603261127.QrC9E9f0-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603261127.QrC9E9f0-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> net/ipv4/devinet.c:2131:13: warning: 'devinet_conf_post_set' used but never defined
2131 | static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
| ^~~~~~~~~~~~~~~~~~~~~
vim +/devinet_conf_post_set +2131 net/ipv4/devinet.c
2130
> 2131 static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
2132 int attr, int new, int old, int index);
2133
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
2026-03-25 20:39 ` Fernando Fernandez Mancera
2026-03-26 3:39 ` kernel test robot
@ 2026-03-26 7:25 ` kernel test robot
2026-03-26 12:08 ` kernel test robot
3 siblings, 0 replies; 6+ messages in thread
From: kernel test robot @ 2026-03-26 7:25 UTC (permalink / raw)
To: Fernando Fernandez Mancera, netdev
Cc: oe-kbuild-all, horms, pabeni, kuba, edumazet, dsahern, davem,
Fernando Fernandez Mancera
Hi Fernando,
kernel test robot noticed the following build errors:
[auto build test ERROR on net-next/main]
url: https://github.com/intel-lab-lkp/linux/commits/Fernando-Fernandez-Mancera/ipv4-ipv4-handle-devconf-post-set-actions-on-netlink-updates/20260326-020953
base: net-next/main
patch link: https://lore.kernel.org/r/20260325161020.3516-2-fmancera%40suse.de
patch subject: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
config: um-randconfig-002-20260326 (https://download.01.org/0day-ci/archive/20260326/202603261543.ZsP9A5JB-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260326/202603261543.ZsP9A5JB-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603261543.ZsP9A5JB-lkp@intel.com/
All errors (new ones prefixed by >>):
/usr/bin/ld: net/ipv4/devinet.o: in function `inet_set_link_af':
>> devinet.c:(.text+0x117d): undefined reference to `devinet_conf_post_set'
collect2: error: ld returned 1 exit status
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
` (2 preceding siblings ...)
2026-03-26 7:25 ` kernel test robot
@ 2026-03-26 12:08 ` kernel test robot
3 siblings, 0 replies; 6+ messages in thread
From: kernel test robot @ 2026-03-26 12:08 UTC (permalink / raw)
To: Fernando Fernandez Mancera, netdev
Cc: llvm, oe-kbuild-all, horms, pabeni, kuba, edumazet, dsahern,
davem, Fernando Fernandez Mancera
Hi Fernando,
kernel test robot noticed the following build warnings:
[auto build test WARNING on net-next/main]
url: https://github.com/intel-lab-lkp/linux/commits/Fernando-Fernandez-Mancera/ipv4-ipv4-handle-devconf-post-set-actions-on-netlink-updates/20260326-020953
base: net-next/main
patch link: https://lore.kernel.org/r/20260325161020.3516-2-fmancera%40suse.de
patch subject: [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates
config: x86_64-buildonly-randconfig-003-20260326 (https://download.01.org/0day-ci/archive/20260326/202603261933.hgl2CPHS-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260326/202603261933.hgl2CPHS-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603261933.hgl2CPHS-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> net/ipv4/devinet.c:2131:13: warning: function 'devinet_conf_post_set' has internal linkage but is not defined [-Wundefined-internal]
2131 | static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
| ^
net/ipv4/devinet.c:2155:8: note: used here
2155 | if (devinet_conf_post_set(net, &in_dev->cnf, nla_type(a), new_value,
| ^
1 warning generated.
vim +/devinet_conf_post_set +2131 net/ipv4/devinet.c
2130
> 2131 static bool devinet_conf_post_set(struct net *net, struct ipv4_devconf *cnf,
2132 int attr, int new, int old, int index);
2133
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 6+ messages in thread
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2026-03-25 16:10 ` [PATCH 2/2 net-next] ipv4: ipv4: handle devconf post-set actions on netlink updates Fernando Fernandez Mancera
2026-03-25 20:39 ` Fernando Fernandez Mancera
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