On 04.07.2025 08:00, Kuniyuki Iwashima wrote:
From: Gabriel Goller g.goller@proxmox.com Date: Thu, 3 Jul 2025 18:01:53 +0200
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 0f1251cce314..ec7fa1e890f1 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -2292,6 +2292,11 @@ conf/all/forwarding - BOOLEAN proxy_ndp - BOOLEAN Do proxy ndp.
+force_forwarding - BOOLEAN
- Enable forwarding on this interface only -- regardless of the setting on
- ``conf/all/forwarding``. When setting ``conf.all.forwarding`` to 0,
- the ``force_forwarding`` flag will be reset on all interfaces.
Please update conf/all/forwarding too as it will be stale after this patch.
I'll change the conf/all/forwarding section from:
IPv4 and IPv6 work differently here; e.g. netfilter must be used to control which interfaces may forward packets and which not.
to:
IPv4 and IPv6 work differently here; the ``force_forwarding`` flag must be used to control which interfaces may forward packets.
I hope that's all right.
fwmark_reflect - BOOLEAN Controls the fwmark of kernel-generated IPv6 reply packets that are not associated with a socket for example, TCP RSTs or ICMPv6 echo replies). diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h index 5aeeed22f35b..5380107e466c 100644 --- a/include/linux/ipv6.h +++ b/include/linux/ipv6.h @@ -19,6 +19,7 @@ struct ipv6_devconf { __s32 forwarding; __s32 disable_policy; __s32 proxy_ndp;
- __s32 force_forwarding;
nit: place force_forwarding just after forwarding.
Agree.
__cacheline_group_end(ipv6_devconf_read_txrx);
__s32 accept_ra; @@ -857,6 +859,15 @@ static void addrconf_forward_change(struct net *net, __s32 newf) idev = __in6_dev_get_rtnl_net(dev); if (idev) { int changed = (!idev->cnf.forwarding) ^ (!newf);
/** With the introduction of force_forwarding, we need to be backwards* compatible, so that means we need to set the force_forwarding flagStrictly backward compatibility is not related I think because the per iface conf is disabled by default, and this is a new behaviour. Maybe simply say
/* Disabling all.forwarding sets 0 to force_forwarding for all interfaces */
Agree.
* on every interface to 0 if net.ipv6.conf.all.forwarding is set to 0.* This allows the global forwarding flag to disable forwarding for* all interfaces.*/if (newf == 0)WRITE_ONCE(idev->cnf.force_forwarding, newf); WRITE_ONCE(idev->cnf.forwarding, newf); if (changed)@@ -5719,6 +5730,7 @@ static void ipv6_store_devconf(const struct ipv6_devconf *cnf, array[DEVCONF_ACCEPT_UNTRACKED_NA] = READ_ONCE(cnf->accept_untracked_na); array[DEVCONF_ACCEPT_RA_MIN_LFT] = READ_ONCE(cnf->accept_ra_min_lft);
- array[DEVCONF_FORCE_FORWARDING] = READ_ONCE(cnf->force_forwarding);
}
[...]
static inline size_t inet6_ifla6_size(void) @@ -6747,6 +6759,78 @@ static int addrconf_sysctl_disable_policy(const struct ctl_table *ctl, int write return ret; }
+static void addrconf_force_forward_change(struct net *net, __s32 newf) +{
- ASSERT_RTNL();
__in6_dev_get_rtnl_net() has the same check so this is not needed.
Agree.
- struct net_device *dev;
- struct inet6_dev *idev;
- for_each_netdev(net, dev) {
idev = __in6_dev_get_rtnl_net(dev);if (idev) {int changed = (!idev->cnf.force_forwarding) ^ (!newf);WRITE_ONCE(idev->cnf.force_forwarding, newf);if (changed) {inet6_netconf_notify_devconf(dev_net(dev), RTM_NEWNETCONF,NETCONFA_FORCE_FORWARDING,dev->ifindex, &idev->cnf);}}- }
+}
+static int addrconf_sysctl_force_forwarding(const struct ctl_table *ctl, int write,
void *buffer, size_t *lenp, loff_t *ppos)+{
- struct inet6_dev *idev = ctl->extra1;
- struct net *net = ctl->extra2;
- int *valp = ctl->data;
- loff_t pos = *ppos;
nit: Please keep the reverse xmas tree order. https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html#local-...
- int new_val = *valp;
- int old_val = *valp;
- int ret;
- struct ctl_table tmp_ctl = *ctl;
same here.
Will do; moved this up.
- tmp_ctl.extra1 = SYSCTL_ZERO;
- tmp_ctl.extra2 = SYSCTL_ONE;
As you are copying *ctl, please specify this in addrconf_sysctl[].
Umm how would I do that? Do you want me to add a comment explaining it? I need extra1 and extra2 to be the network device so that I can set NETCONFA_FORCE_FORWARDING but I also want to use proc_douintvec_minmax.
- tmp_ctl.data = &new_val;
- ret = proc_douintvec_minmax(&tmp_ctl, write, buffer, lenp, ppos);
- if (write && old_val != new_val) {
if (!rtnl_net_trylock(net))return restart_syscall();if (valp == &net->ipv6.devconf_dflt->force_forwarding) {inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,NETCONFA_FORCE_FORWARDING,NETCONFA_IFINDEX_DEFAULT,net->ipv6.devconf_dflt);} else if (valp == &net->ipv6.devconf_all->force_forwarding) {inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,NETCONFA_FORCE_FORWARDING,NETCONFA_IFINDEX_ALL,net->ipv6.devconf_all);addrconf_force_forward_change(net, new_val);} else {inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,NETCONFA_FORCE_FORWARDING,idev->dev->ifindex,&idev->cnf);}rtnl_net_unlock(net);- }
- if (write)
WRITE_ONCE(*valp, new_val);- if (ret)
*ppos = pos;- return ret;
+}
static int minus_one = -1; static const int two_five_five = 255; static u32 ioam6_if_id_max = U16_MAX; @@ -7217,6 +7301,13 @@ static const struct ctl_table addrconf_sysctl[] = { .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_TWO, },
- {
.procname = "force_forwarding",.data = &ipv6_devconf.force_forwarding,.maxlen = sizeof(int),.mode = 0644,.proc_handler = addrconf_sysctl_force_forwarding,Here for extra{1,2}.
See above.
- },
}; static int __addrconf_sysctl_register(struct net *net, char *dev_name, diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 7bd29a9ff0db..440b9efced72 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -509,7 +509,8 @@ int ip6_forward(struct sk_buff *skb) u32 mtu;
idev = __in6_dev_get_safely(dev_get_by_index_rcu(net, IP6CB(skb)->iif));
- if (READ_ONCE(net->ipv6.devconf_all->forwarding) == 0)
- if (idev && !READ_ONCE(idev->cnf.force_forwarding) &&
!READ_ONCE(net->ipv6.devconf_all->forwarding))Now this ignores devconf_all when !idev whose dev was not found or has not had a valid mtu.
if (!READ_ONCE(net->ipv6.devconf_all->forwarding) && (!idev || !READ_ONCE(idev->cnf.force_forwarding)))
Oof yeah, you're right this is my mistake. I'll use your solution.
Thanks for the review!