Commit e687ad60af09 ("netfilter: add netfilter ingress hook after
handle_ing() under unique static key") introduced the ability to
classify packets on ingress.
Allow the same on egress.
The need for this arose because I had to filter egress packets which do
not match a specific ethertype. The most common solution appears to be
to enslave the interface to a bridge and use ebtables, but that's
cumbersome to configure and comes with a (small) performance penalty.
An alternative approach is tc, but that doesn't afford equivalent
matching options as netfilter. A bit of googling reveals that more
people have expressed a desire for egress filtering in the past:
https://www.spinics.net/lists/netfilter/msg50038.html
https://unix.stackexchange.com/questions/512371
An egress hook therefore seems like an obvious addition.
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
include/linux/netdevice.h | 4 ++++
include/linux/netfilter_netdev.h | 27 +++++++++++++++++++++++++++
include/uapi/linux/netfilter.h | 1 +
net/core/dev.c | 25 ++++++++++++++++++++-----
net/netfilter/Kconfig | 8 ++++++++
net/netfilter/core.c | 24 ++++++++++++++++++++----
net/netfilter/nft_chain_filter.c | 4 +++-
7 files changed, 83 insertions(+), 10 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index bc6914ea3faf..111107aed50b 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1720,6 +1720,7 @@ enum netdev_priv_flags {
* @xps_maps: XXX: need comments on this one
* @miniq_egress: clsact qdisc specific data for
* egress processing
+ * @nf_hooks_egress: netfilter hooks executed for egress packets
* @watchdog_timeo: Represents the timeout that is used by
* the watchdog (see dev_watchdog())
* @watchdog_timer: List of timers
@@ -1981,6 +1982,9 @@ struct net_device {
#ifdef CONFIG_NET_CLS_ACT
struct mini_Qdisc __rcu *miniq_egress;
#endif
+#ifdef CONFIG_NETFILTER_EGRESS
+ struct nf_hook_entries __rcu *nf_hooks_egress;
+#endif
/* These may be needed for future network-power-down code. */
struct timer_list watchdog_timer;
diff --git a/include/linux/netfilter_netdev.h b/include/linux/netfilter_netdev.h
index 49e26479642e..92d3611a782e 100644
--- a/include/linux/netfilter_netdev.h
+++ b/include/linux/netfilter_netdev.h
@@ -47,6 +47,9 @@ static inline void nf_hook_netdev_init(struct net_device *dev)
#ifdef CONFIG_NETFILTER_INGRESS
RCU_INIT_POINTER(dev->nf_hooks_ingress, NULL);
#endif
+#ifdef CONFIG_NETFILTER_EGRESS
+ RCU_INIT_POINTER(dev->nf_hooks_egress, NULL);
+#endif
}
#ifdef CONFIG_NETFILTER_INGRESS
@@ -72,4 +75,28 @@ static inline int nf_hook_ingress(struct sk_buff *skb)
return 0;
}
#endif /* CONFIG_NETFILTER_INGRESS */
+
+#ifdef CONFIG_NETFILTER_EGRESS
+static inline bool nf_hook_egress_active(const struct sk_buff *skb)
+{
+ return nf_hook_netdev_active(NF_NETDEV_EGRESS,
+ skb->dev->nf_hooks_egress);
+}
+
+static inline int nf_hook_egress(struct sk_buff *skb)
+{
+ return nf_hook_netdev(skb, NF_NETDEV_EGRESS,
+ skb->dev->nf_hooks_egress);
+}
+#else /* CONFIG_NETFILTER_EGRESS */
+static inline int nf_hook_egress_active(struct sk_buff *skb)
+{
+ return 0;
+}
+
+static inline int nf_hook_egress(struct sk_buff *skb)
+{
+ return 0;
+}
+#endif /* CONFIG_NETFILTER_EGRESS */
#endif /* _NETFILTER_INGRESS_H_ */
diff --git a/include/uapi/linux/netfilter.h b/include/uapi/linux/netfilter.h
index ca9e63d6e0e4..d1616574c54f 100644
--- a/include/uapi/linux/netfilter.h
+++ b/include/uapi/linux/netfilter.h
@@ -50,6 +50,7 @@ enum nf_inet_hooks {
enum nf_dev_hooks {
NF_NETDEV_INGRESS,
+ NF_NETDEV_EGRESS,
NF_NETDEV_NUMHOOKS
};
diff --git a/net/core/dev.c b/net/core/dev.c
index e4976f68f2dd..d1e48fc4ae5c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3811,10 +3811,10 @@ int dev_loopback_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
}
EXPORT_SYMBOL(dev_loopback_xmit);
-#ifdef CONFIG_NET_EGRESS
static struct sk_buff *
sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
{
+#ifdef CONFIG_NET_CLS_ACT
struct mini_Qdisc *miniq = rcu_dereference_bh(dev->miniq_egress);
struct tcf_result cl_res;
@@ -3848,10 +3848,22 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
default:
break;
}
-
+#endif /* CONFIG_NET_CLS_ACT */
return skb;
}
-#endif /* CONFIG_NET_EGRESS */
+
+static int nf_egress(struct sk_buff *skb)
+{
+ if (nf_hook_egress_active(skb)) {
+ int ret;
+
+ rcu_read_lock();
+ ret = nf_hook_egress(skb);
+ rcu_read_unlock();
+ return ret;
+ }
+ return 0;
+}
#ifdef CONFIG_XPS
static int __get_xps_queue_idx(struct net_device *dev, struct sk_buff *skb,
@@ -4039,13 +4051,16 @@ static int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
qdisc_pkt_len_init(skb);
#ifdef CONFIG_NET_CLS_ACT
skb->tc_at_ingress = 0;
-# ifdef CONFIG_NET_EGRESS
+#endif
+#ifdef CONFIG_NET_EGRESS
if (static_branch_unlikely(&egress_needed_key)) {
skb = sch_handle_egress(skb, &rc, dev);
if (!skb)
goto out;
+
+ if (nf_egress(skb) < 0)
+ goto out;
}
-# endif
#endif
/* If device/qdisc don't need skb->dst, release it right now while
* its hot in this cpu cache.
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 91efae88e8c2..a6ae141ec77e 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -10,6 +10,14 @@ config NETFILTER_INGRESS
This allows you to classify packets from ingress using the Netfilter
infrastructure.
+config NETFILTER_EGRESS
+ bool "Netfilter egress support"
+ default y
+ select NET_EGRESS
+ help
+ This allows you to classify packets before transmission using the
+ Netfilter infrastructure.
+
config NETFILTER_NETLINK
tristate
diff --git a/net/netfilter/core.c b/net/netfilter/core.c
index 78f046ec506f..85e9c959aba7 100644
--- a/net/netfilter/core.c
+++ b/net/netfilter/core.c
@@ -306,6 +306,12 @@ nf_hook_entry_head(struct net *net, int pf, unsigned int hooknum,
if (dev && dev_net(dev) == net)
return &dev->nf_hooks_ingress;
}
+#endif
+#ifdef CONFIG_NETFILTER_EGRESS
+ if (hooknum == NF_NETDEV_EGRESS) {
+ if (dev && dev_net(dev) == net)
+ return &dev->nf_hooks_egress;
+ }
#endif
WARN_ON_ONCE(1);
return NULL;
@@ -318,11 +324,13 @@ static int __nf_register_net_hook(struct net *net, int pf,
struct nf_hook_entries __rcu **pp;
if (pf == NFPROTO_NETDEV) {
-#ifndef CONFIG_NETFILTER_INGRESS
- if (reg->hooknum == NF_NETDEV_INGRESS)
+ if ((!IS_ENABLED(CONFIG_NETFILTER_INGRESS) &&
+ reg->hooknum == NF_NETDEV_INGRESS) ||
+ (!IS_ENABLED(CONFIG_NETFILTER_EGRESS) &&
+ reg->hooknum == NF_NETDEV_EGRESS))
return -EOPNOTSUPP;
-#endif
- if (reg->hooknum != NF_NETDEV_INGRESS ||
+ if ((reg->hooknum != NF_NETDEV_INGRESS &&
+ reg->hooknum != NF_NETDEV_EGRESS) ||
!reg->dev || dev_net(reg->dev) != net)
return -EINVAL;
}
@@ -348,6 +356,10 @@ static int __nf_register_net_hook(struct net *net, int pf,
if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
net_inc_ingress_queue();
#endif
+#ifdef CONFIG_NETFILTER_EGRESS
+ if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_EGRESS)
+ net_inc_egress_queue();
+#endif
#ifdef CONFIG_JUMP_LABEL
static_key_slow_inc(&nf_hooks_needed[pf][reg->hooknum]);
#endif
@@ -406,6 +418,10 @@ static void __nf_unregister_net_hook(struct net *net, int pf,
if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
net_dec_ingress_queue();
#endif
+#ifdef CONFIG_NETFILTER_EGRESS
+ if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_EGRESS)
+ net_dec_egress_queue();
+#endif
#ifdef CONFIG_JUMP_LABEL
static_key_slow_dec(&nf_hooks_needed[pf][reg->hooknum]);
#endif
diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
index c78d01bc02e9..67ce6dbb5496 100644
--- a/net/netfilter/nft_chain_filter.c
+++ b/net/netfilter/nft_chain_filter.c
@@ -277,9 +277,11 @@ static const struct nft_chain_type nft_chain_filter_netdev = {
.name = "filter",
.type = NFT_CHAIN_T_DEFAULT,
.family = NFPROTO_NETDEV,
- .hook_mask = (1 << NF_NETDEV_INGRESS),
+ .hook_mask = (1 << NF_NETDEV_INGRESS) |
+ (1 << NF_NETDEV_EGRESS),
.hooks = {
[NF_NETDEV_INGRESS] = nft_do_chain_netdev,
+ [NF_NETDEV_EGRESS] = nft_do_chain_netdev,
},
};
--
2.23.0
