[PATCH v4 net-next 7/9] net: ipv4: listified version of ip_rcv

[Edward Cree <ecree@solarflare.com>]

Also involved adding a way to run a netfilter hook over a list of packets.
 Rather than attempting to make netfilter know about lists (which would be
 a major project in itself) we just let it call the regular okfn (in this
 case ip_rcv_finish()) for any packets it steals, and have it give us back
 a list of packets it's synchronously accepted (which normally NF_HOOK
 would automatically call okfn() on, but we want to be able to potentially
 pass the list to a listified version of okfn().)
The netfilter hooks themselves are indirect calls that still happen per-
 packet (see nf_hook_entry_hookfn()), but again, changing that can be left
 for future work.

There is potential for out-of-order receives if the netfilter hook ends up
 synchronously stealing packets, as they will be processed before any
 accepts earlier in the list.  However, it was already possible for an
 asynchronous accept to cause out-of-order receives, so presumably this is
 considered OK.

Signed-off-by: Edward Cree <ecree@solarflare.com>
---
 include/linux/netdevice.h |  3 +++
 include/linux/netfilter.h | 22 +++++++++++++++
 include/net/ip.h          |  2 ++
 net/core/dev.c            |  8 +++---
 net/ipv4/af_inet.c        |  1 +
 net/ipv4/ip_input.c       | 68 ++++++++++++++++++++++++++++++++++++++++++-----
 6 files changed, 94 insertions(+), 10 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index e104b2e4a735..fe81a2bfcd08 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2291,6 +2291,9 @@ struct packet_type {
 					 struct net_device *,
 					 struct packet_type *,
 					 struct net_device *);
+	void			(*list_func) (struct list_head *,
+					      struct packet_type *,
+					      struct net_device *);
 	bool			(*id_match)(struct packet_type *ptype,
 					    struct sock *sk);
 	void			*af_packet_priv;
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index dd2052f0efb7..5a5e0a2ab2a3 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -288,6 +288,20 @@ NF_HOOK(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk, struct
 	return ret;
 }
 
+static inline void
+NF_HOOK_LIST(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk,
+	     struct list_head *head, struct net_device *in, struct net_device *out,
+	     int (*okfn)(struct net *, struct sock *, struct sk_buff *))
+{
+	struct sk_buff *skb, *next;
+
+	list_for_each_entry_safe(skb, next, head, list) {
+		int ret = nf_hook(pf, hook, net, sk, skb, in, out, okfn);
+		if (ret != 1)
+			list_del(&skb->list);
+	}
+}
+
 /* Call setsockopt() */
 int nf_setsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,
 		  unsigned int len);
@@ -369,6 +383,14 @@ NF_HOOK(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk,
 	return okfn(net, sk, skb);
 }
 
+static inline void
+NF_HOOK_LIST(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk,
+	     struct list_head *head, struct net_device *in, struct net_device *out,
+	     int (*okfn)(struct net *, struct sock *, struct sk_buff *))
+{
+	/* nothing to do */
+}
+
 static inline int nf_hook(u_int8_t pf, unsigned int hook, struct net *net,
 			  struct sock *sk, struct sk_buff *skb,
 			  struct net_device *indev, struct net_device *outdev,
diff --git a/include/net/ip.h b/include/net/ip.h
index 0d2281b4b27a..1de72f9cb23c 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -138,6 +138,8 @@ int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk,
 			  struct ip_options_rcu *opt);
 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 	   struct net_device *orig_dev);
+void ip_list_rcv(struct list_head *head, struct packet_type *pt,
+		 struct net_device *orig_dev);
 int ip_local_deliver(struct sk_buff *skb);
 int ip_mr_input(struct sk_buff *skb);
 int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb);
diff --git a/net/core/dev.c b/net/core/dev.c
index edd67b1f1e12..4c5ebfab9bc8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4692,9 +4692,11 @@ static inline void __netif_receive_skb_list_ptype(struct list_head *head,
 		return;
 	if (list_empty(head))
 		return;
-
-	list_for_each_entry_safe(skb, next, head, list)
-		pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
+	if (pt_prev->list_func != NULL)
+		pt_prev->list_func(head, pt_prev, orig_dev);
+	else
+		list_for_each_entry_safe(skb, next, head, list)
+			pt_prev->func(skb, skb->dev, pt_prev, orig_dev);
 }
 
 static void __netif_receive_skb_list_core(struct list_head *head, bool pfmemalloc)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 06b218a2870f..3ff7659c9afd 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1882,6 +1882,7 @@ fs_initcall(ipv4_offload_init);
 static struct packet_type ip_packet_type __read_mostly = {
 	.type = cpu_to_be16(ETH_P_IP),
 	.func = ip_rcv,
+	.list_func = ip_list_rcv,
 };
 
 static int __init inet_init(void)
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 7582713dd18f..914240830bdf 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -408,10 +408,9 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 /*
  * 	Main IP Receive routine.
  */
-int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
+static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
 {
 	const struct iphdr *iph;
-	struct net *net;
 	u32 len;
 
 	/* When the interface is in promisc. mode, drop all the crap
@@ -421,7 +420,6 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 		goto drop;
 
 
-	net = dev_net(dev);
 	__IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len);
 
 	skb = skb_share_check(skb, GFP_ATOMIC);
@@ -489,9 +487,7 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 	/* Must drop socket now because of tproxy. */
 	skb_orphan(skb);
 
-	return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
-		       net, NULL, skb, dev, NULL,
-		       ip_rcv_finish);
+	return skb;
 
 csum_error:
 	__IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS);
@@ -500,5 +496,63 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 drop:
 	kfree_skb(skb);
 out:
-	return NET_RX_DROP;
+	return NULL;
+}
+
+/*
+ * IP receive entry point
+ */
+int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
+	   struct net_device *orig_dev)
+{
+	struct net *net = dev_net(dev);
+
+	skb = ip_rcv_core(skb, net);
+	if (skb == NULL)
+		return NET_RX_DROP;
+	return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
+		       net, NULL, skb, dev, NULL,
+		       ip_rcv_finish);
+}
+
+static void ip_sublist_rcv(struct list_head *head, struct net_device *dev,
+			   struct net *net)
+{
+	struct sk_buff *skb, *next;
+
+	NF_HOOK_LIST(NFPROTO_IPV4, NF_INET_PRE_ROUTING, net, NULL,
+		     head, dev, NULL, ip_rcv_finish);
+	list_for_each_entry_safe(skb, next, head, list)
+		ip_rcv_finish(net, NULL, skb);
+}
+
+/* Receive a list of IP packets */
+void ip_list_rcv(struct list_head *head, struct packet_type *pt,
+		 struct net_device *orig_dev)
+{
+	struct net_device *curr_dev = NULL;
+	struct net *curr_net = NULL;
+	struct sk_buff *skb, *next;
+	struct list_head sublist;
+
+	list_for_each_entry_safe(skb, next, head, list) {
+		struct net_device *dev = skb->dev;
+		struct net *net = dev_net(dev);
+
+		skb = ip_rcv_core(skb, net);
+		if (skb == NULL)
+			continue;
+
+		if (curr_dev != dev || curr_net != net) {
+			/* dispatch old sublist */
+			list_cut_before(&sublist, head, &skb->list);
+			if (!list_empty(&sublist))
+				ip_sublist_rcv(&sublist, dev, net);
+			/* start new sublist */
+			curr_dev = dev;
+			curr_net = net;
+		}
+	}
+	/* dispatch final sublist */
+	ip_sublist_rcv(head, curr_dev, curr_net);
 }