Message-Id: <1372699440-2289-1-git-send-email-dborkman@redhat.com>
Date:	Mon,  1 Jul 2013 19:24:00 +0200
From:	Daniel Borkmann <dborkman@...hat.com>
To:	davem@...emloft.net
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: [PATCH net-next] net: gre: move GSO functions to gre_offload

Similarly to TCP/UDP offloading, move all related GRE functions to
gre_offload.c to make things more explicit and similar to the rest
of the code.

Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
---
 When net is merged into net-next, this will clash with bd8a7036c06cf1577 ("gre:
 fix a possible skb leak") in gre_gso_segment() as kfree_skb() is being replaced
 with kfree_skb_list() in one occurence. How would you like to handle this Dave?
 This patch is not really urgent though, but maybe we could get this still in
 before net-next closes.

 include/net/gre.h      |   4 +
 net/ipv4/Makefile      |   1 +
 net/ipv4/gre.c         | 514 -------------------------------------------------
 net/ipv4/gre_demux.c   | 414 +++++++++++++++++++++++++++++++++++++++
 net/ipv4/gre_offload.c | 127 ++++++++++++
 5 files changed, 546 insertions(+), 514 deletions(-)
 delete mode 100644 net/ipv4/gre.c
 create mode 100644 net/ipv4/gre_demux.c
 create mode 100644 net/ipv4/gre_offload.c

diff --git a/include/net/gre.h b/include/net/gre.h
index a5a4ddf..57e4afd 100644
--- a/include/net/gre.h
+++ b/include/net/gre.h
@@ -32,6 +32,10 @@ struct gre_cisco_protocol {
 
 int gre_cisco_register(struct gre_cisco_protocol *proto);
 int gre_cisco_unregister(struct gre_cisco_protocol *proto);
+
+int gre_offload_init(void);
+void gre_offload_exit(void);
+
 void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
 		      int hdr_len);
 struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum);
diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile
index 86ded0b..4b81e91 100644
--- a/net/ipv4/Makefile
+++ b/net/ipv4/Makefile
@@ -19,6 +19,7 @@ obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_IP_MULTIPLE_TABLES) += fib_rules.o
 obj-$(CONFIG_IP_MROUTE) += ipmr.o
 obj-$(CONFIG_NET_IPIP) += ipip.o
+gre-y := gre_demux.o gre_offload.o
 obj-$(CONFIG_NET_IPGRE_DEMUX) += gre.o
 obj-$(CONFIG_NET_IPGRE) += ip_gre.o
 obj-$(CONFIG_NET_IPVTI) += ip_vti.o
diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
deleted file mode 100644
index ba4803e..0000000
--- a/net/ipv4/gre.c
+++ /dev/null
@@ -1,514 +0,0 @@
-/*
- *	GRE over IPv4 demultiplexer driver
- *
- *	Authors: Dmitry Kozlov (xeb@...l.ru)
- *
- *	This program is free software; you can redistribute it and/or
- *	modify it under the terms of the GNU General Public License
- *	as published by the Free Software Foundation; either version
- *	2 of the License, or (at your option) any later version.
- *
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/module.h>
-#include <linux/if.h>
-#include <linux/icmp.h>
-#include <linux/kernel.h>
-#include <linux/kmod.h>
-#include <linux/skbuff.h>
-#include <linux/in.h>
-#include <linux/ip.h>
-#include <linux/netdevice.h>
-#include <linux/if_tunnel.h>
-#include <linux/spinlock.h>
-#include <net/protocol.h>
-#include <net/gre.h>
-
-#include <net/icmp.h>
-#include <net/route.h>
-#include <net/xfrm.h>
-
-static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
-static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX];
-
-int gre_add_protocol(const struct gre_protocol *proto, u8 version)
-{
-	if (version >= GREPROTO_MAX)
-		return -EINVAL;
-
-	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
-		0 : -EBUSY;
-}
-EXPORT_SYMBOL_GPL(gre_add_protocol);
-
-int gre_del_protocol(const struct gre_protocol *proto, u8 version)
-{
-	int ret;
-
-	if (version >= GREPROTO_MAX)
-		return -EINVAL;
-
-	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
-		0 : -EBUSY;
-
-	if (ret)
-		return ret;
-
-	synchronize_rcu();
-	return 0;
-}
-EXPORT_SYMBOL_GPL(gre_del_protocol);
-
-void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
-		      int hdr_len)
-{
-	struct gre_base_hdr *greh;
-
-	skb_push(skb, hdr_len);
-
-	greh = (struct gre_base_hdr *)skb->data;
-	greh->flags = tnl_flags_to_gre_flags(tpi->flags);
-	greh->protocol = tpi->proto;
-
-	if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) {
-		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
-
-		if (tpi->flags&TUNNEL_SEQ) {
-			*ptr = tpi->seq;
-			ptr--;
-		}
-		if (tpi->flags&TUNNEL_KEY) {
-			*ptr = tpi->key;
-			ptr--;
-		}
-		if (tpi->flags&TUNNEL_CSUM &&
-		    !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
-			*ptr = 0;
-			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
-								 skb->len, 0));
-		}
-	}
-}
-EXPORT_SYMBOL_GPL(gre_build_header);
-
-struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum)
-{
-	int err;
-
-	if (likely(!skb->encapsulation)) {
-		skb_reset_inner_headers(skb);
-		skb->encapsulation = 1;
-	}
-
-	if (skb_is_gso(skb)) {
-		err = skb_unclone(skb, GFP_ATOMIC);
-		if (unlikely(err))
-			goto error;
-		skb_shinfo(skb)->gso_type |= SKB_GSO_GRE;
-		return skb;
-	} else if (skb->ip_summed == CHECKSUM_PARTIAL && gre_csum) {
-		err = skb_checksum_help(skb);
-		if (unlikely(err))
-			goto error;
-	} else if (skb->ip_summed != CHECKSUM_PARTIAL)
-		skb->ip_summed = CHECKSUM_NONE;
-
-	return skb;
-error:
-	kfree_skb(skb);
-	return ERR_PTR(err);
-}
-EXPORT_SYMBOL_GPL(gre_handle_offloads);
-
-static __sum16 check_checksum(struct sk_buff *skb)
-{
-	__sum16 csum = 0;
-
-	switch (skb->ip_summed) {
-	case CHECKSUM_COMPLETE:
-		csum = csum_fold(skb->csum);
-
-		if (!csum)
-			break;
-		/* Fall through. */
-
-	case CHECKSUM_NONE:
-		skb->csum = 0;
-		csum = __skb_checksum_complete(skb);
-		skb->ip_summed = CHECKSUM_COMPLETE;
-		break;
-	}
-
-	return csum;
-}
-
-static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
-			    bool *csum_err)
-{
-	unsigned int ip_hlen = ip_hdrlen(skb);
-	const struct gre_base_hdr *greh;
-	__be32 *options;
-	int hdr_len;
-
-	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
-		return -EINVAL;
-
-	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
-	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
-		return -EINVAL;
-
-	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
-	hdr_len = ip_gre_calc_hlen(tpi->flags);
-
-	if (!pskb_may_pull(skb, hdr_len))
-		return -EINVAL;
-
-	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
-	tpi->proto = greh->protocol;
-
-	options = (__be32 *)(greh + 1);
-	if (greh->flags & GRE_CSUM) {
-		if (check_checksum(skb)) {
-			*csum_err = true;
-			return -EINVAL;
-		}
-		options++;
-	}
-
-	if (greh->flags & GRE_KEY) {
-		tpi->key = *options;
-		options++;
-	} else
-		tpi->key = 0;
-
-	if (unlikely(greh->flags & GRE_SEQ)) {
-		tpi->seq = *options;
-		options++;
-	} else
-		tpi->seq = 0;
-
-	/* WCCP version 1 and 2 protocol decoding.
-	 * - Change protocol to IP
-	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
-	 */
-	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
-		tpi->proto = htons(ETH_P_IP);
-		if ((*(u8 *)options & 0xF0) != 0x40) {
-			hdr_len += 4;
-			if (!pskb_may_pull(skb, hdr_len))
-				return -EINVAL;
-		}
-	}
-
-	return iptunnel_pull_header(skb, hdr_len, tpi->proto);
-}
-
-static int gre_cisco_rcv(struct sk_buff *skb)
-{
-	struct tnl_ptk_info tpi;
-	int i;
-	bool csum_err = false;
-
-	if (parse_gre_header(skb, &tpi, &csum_err) < 0)
-		goto drop;
-
-	rcu_read_lock();
-	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
-		struct gre_cisco_protocol *proto;
-		int ret;
-
-		proto = rcu_dereference(gre_cisco_proto_list[i]);
-		if (!proto)
-			continue;
-		ret = proto->handler(skb, &tpi);
-		if (ret == PACKET_RCVD) {
-			rcu_read_unlock();
-			return 0;
-		}
-	}
-	rcu_read_unlock();
-
-	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
-drop:
-	kfree_skb(skb);
-	return 0;
-}
-
-static void gre_cisco_err(struct sk_buff *skb, u32 info)
-{
-	/* All the routers (except for Linux) return only
-	 * 8 bytes of packet payload. It means, that precise relaying of
-	 * ICMP in the real Internet is absolutely infeasible.
-	 *
-	 * Moreover, Cisco "wise men" put GRE key to the third word
-	 * in GRE header. It makes impossible maintaining even soft
-	 * state for keyed
-	 * GRE tunnels with enabled checksum. Tell them "thank you".
-	 *
-	 * Well, I wonder, rfc1812 was written by Cisco employee,
-	 * what the hell these idiots break standards established
-	 * by themselves???
-	 */
-
-	const int type = icmp_hdr(skb)->type;
-	const int code = icmp_hdr(skb)->code;
-	struct tnl_ptk_info tpi;
-	bool csum_err = false;
-	int i;
-
-	if (parse_gre_header(skb, &tpi, &csum_err)) {
-		if (!csum_err)		/* ignore csum errors. */
-			return;
-	}
-
-	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
-				skb->dev->ifindex, 0, IPPROTO_GRE, 0);
-		return;
-	}
-	if (type == ICMP_REDIRECT) {
-		ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
-				IPPROTO_GRE, 0);
-		return;
-	}
-
-	rcu_read_lock();
-	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
-		struct gre_cisco_protocol *proto;
-
-		proto = rcu_dereference(gre_cisco_proto_list[i]);
-		if (!proto)
-			continue;
-
-		if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
-			goto out;
-
-	}
-out:
-	rcu_read_unlock();
-}
-
-static int gre_rcv(struct sk_buff *skb)
-{
-	const struct gre_protocol *proto;
-	u8 ver;
-	int ret;
-
-	if (!pskb_may_pull(skb, 12))
-		goto drop;
-
-	ver = skb->data[1]&0x7f;
-	if (ver >= GREPROTO_MAX)
-		goto drop;
-
-	rcu_read_lock();
-	proto = rcu_dereference(gre_proto[ver]);
-	if (!proto || !proto->handler)
-		goto drop_unlock;
-	ret = proto->handler(skb);
-	rcu_read_unlock();
-	return ret;
-
-drop_unlock:
-	rcu_read_unlock();
-drop:
-	kfree_skb(skb);
-	return NET_RX_DROP;
-}
-
-static void gre_err(struct sk_buff *skb, u32 info)
-{
-	const struct gre_protocol *proto;
-	const struct iphdr *iph = (const struct iphdr *)skb->data;
-	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
-
-	if (ver >= GREPROTO_MAX)
-		return;
-
-	rcu_read_lock();
-	proto = rcu_dereference(gre_proto[ver]);
-	if (proto && proto->err_handler)
-		proto->err_handler(skb, info);
-	rcu_read_unlock();
-}
-
-static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
-				       netdev_features_t features)
-{
-	struct sk_buff *segs = ERR_PTR(-EINVAL);
-	netdev_features_t enc_features;
-	int ghl = GRE_HEADER_SECTION;
-	struct gre_base_hdr *greh;
-	int mac_len = skb->mac_len;
-	__be16 protocol = skb->protocol;
-	int tnl_hlen;
-	bool csum;
-
-	if (unlikely(skb_shinfo(skb)->gso_type &
-				~(SKB_GSO_TCPV4 |
-				  SKB_GSO_TCPV6 |
-				  SKB_GSO_UDP |
-				  SKB_GSO_DODGY |
-				  SKB_GSO_TCP_ECN |
-				  SKB_GSO_GRE)))
-		goto out;
-
-	if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
-		goto out;
-
-	greh = (struct gre_base_hdr *)skb_transport_header(skb);
-
-	if (greh->flags & GRE_KEY)
-		ghl += GRE_HEADER_SECTION;
-	if (greh->flags & GRE_SEQ)
-		ghl += GRE_HEADER_SECTION;
-	if (greh->flags & GRE_CSUM) {
-		ghl += GRE_HEADER_SECTION;
-		csum = true;
-	} else
-		csum = false;
-
-	/* setup inner skb. */
-	skb->protocol = greh->protocol;
-	skb->encapsulation = 0;
-
-	if (unlikely(!pskb_may_pull(skb, ghl)))
-		goto out;
-	__skb_pull(skb, ghl);
-	skb_reset_mac_header(skb);
-	skb_set_network_header(skb, skb_inner_network_offset(skb));
-	skb->mac_len = skb_inner_network_offset(skb);
-
-	/* segment inner packet. */
-	enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
-	segs = skb_mac_gso_segment(skb, enc_features);
-	if (!segs || IS_ERR(segs))
-		goto out;
-
-	skb = segs;
-	tnl_hlen = skb_tnl_header_len(skb);
-	do {
-		__skb_push(skb, ghl);
-		if (csum) {
-			__be32 *pcsum;
-
-			if (skb_has_shared_frag(skb)) {
-				int err;
-
-				err = __skb_linearize(skb);
-				if (err) {
-					kfree_skb(segs);
-					segs = ERR_PTR(err);
-					goto out;
-				}
-			}
-
-			greh = (struct gre_base_hdr *)(skb->data);
-			pcsum = (__be32 *)(greh + 1);
-			*pcsum = 0;
-			*(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
-		}
-		__skb_push(skb, tnl_hlen - ghl);
-
-		skb_reset_mac_header(skb);
-		skb_set_network_header(skb, mac_len);
-		skb->mac_len = mac_len;
-		skb->protocol = protocol;
-	} while ((skb = skb->next));
-out:
-	return segs;
-}
-
-static int gre_gso_send_check(struct sk_buff *skb)
-{
-	if (!skb->encapsulation)
-		return -EINVAL;
-	return 0;
-}
-
-static const struct net_protocol net_gre_protocol = {
-	.handler     = gre_rcv,
-	.err_handler = gre_err,
-	.netns_ok    = 1,
-};
-
-static const struct net_offload gre_offload = {
-	.callbacks = {
-		.gso_send_check =	gre_gso_send_check,
-		.gso_segment    =	gre_gso_segment,
-	},
-};
-
-static const struct gre_protocol ipgre_protocol = {
-	.handler     = gre_cisco_rcv,
-	.err_handler = gre_cisco_err,
-};
-
-int gre_cisco_register(struct gre_cisco_protocol *newp)
-{
-	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
-					    &gre_cisco_proto_list[newp->priority];
-
-	return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
-}
-EXPORT_SYMBOL_GPL(gre_cisco_register);
-
-int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
-{
-	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
-					    &gre_cisco_proto_list[del_proto->priority];
-	int ret;
-
-	ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;
-
-	if (ret)
-		return ret;
-
-	synchronize_net();
-	return 0;
-}
-EXPORT_SYMBOL_GPL(gre_cisco_unregister);
-
-static int __init gre_init(void)
-{
-	pr_info("GRE over IPv4 demultiplexor driver\n");
-
-	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
-		pr_err("can't add protocol\n");
-		goto err;
-	}
-
-	if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
-		pr_info("%s: can't add ipgre handler\n", __func__);
-		goto err_gre;
-	}
-
-	if (inet_add_offload(&gre_offload, IPPROTO_GRE)) {
-		pr_err("can't add protocol offload\n");
-		goto err_gso;
-	}
-
-	return 0;
-err_gso:
-	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
-err_gre:
-	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
-err:
-	return -EAGAIN;
-}
-
-static void __exit gre_exit(void)
-{
-	inet_del_offload(&gre_offload, IPPROTO_GRE);
-	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
-	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
-}
-
-module_init(gre_init);
-module_exit(gre_exit);
-
-MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
-MODULE_AUTHOR("D. Kozlov (xeb@...l.ru)");
-MODULE_LICENSE("GPL");
diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
new file mode 100644
index 0000000..736c9fc3
--- /dev/null
+++ b/net/ipv4/gre_demux.c
@@ -0,0 +1,414 @@
+/*
+ *	GRE over IPv4 demultiplexer driver
+ *
+ *	Authors: Dmitry Kozlov (xeb@...l.ru)
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/if.h>
+#include <linux/icmp.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/skbuff.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/netdevice.h>
+#include <linux/if_tunnel.h>
+#include <linux/spinlock.h>
+#include <net/protocol.h>
+#include <net/gre.h>
+
+#include <net/icmp.h>
+#include <net/route.h>
+#include <net/xfrm.h>
+
+static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
+static struct gre_cisco_protocol __rcu *gre_cisco_proto_list[GRE_IP_PROTO_MAX];
+
+int gre_add_protocol(const struct gre_protocol *proto, u8 version)
+{
+	if (version >= GREPROTO_MAX)
+		return -EINVAL;
+
+	return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
+		0 : -EBUSY;
+}
+EXPORT_SYMBOL_GPL(gre_add_protocol);
+
+int gre_del_protocol(const struct gre_protocol *proto, u8 version)
+{
+	int ret;
+
+	if (version >= GREPROTO_MAX)
+		return -EINVAL;
+
+	ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
+		0 : -EBUSY;
+
+	if (ret)
+		return ret;
+
+	synchronize_rcu();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gre_del_protocol);
+
+void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
+		      int hdr_len)
+{
+	struct gre_base_hdr *greh;
+
+	skb_push(skb, hdr_len);
+
+	greh = (struct gre_base_hdr *)skb->data;
+	greh->flags = tnl_flags_to_gre_flags(tpi->flags);
+	greh->protocol = tpi->proto;
+
+	if (tpi->flags&(TUNNEL_KEY|TUNNEL_CSUM|TUNNEL_SEQ)) {
+		__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
+
+		if (tpi->flags&TUNNEL_SEQ) {
+			*ptr = tpi->seq;
+			ptr--;
+		}
+		if (tpi->flags&TUNNEL_KEY) {
+			*ptr = tpi->key;
+			ptr--;
+		}
+		if (tpi->flags&TUNNEL_CSUM &&
+		    !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
+			*ptr = 0;
+			*(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
+								 skb->len, 0));
+		}
+	}
+}
+EXPORT_SYMBOL_GPL(gre_build_header);
+
+struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum)
+{
+	int err;
+
+	if (likely(!skb->encapsulation)) {
+		skb_reset_inner_headers(skb);
+		skb->encapsulation = 1;
+	}
+
+	if (skb_is_gso(skb)) {
+		err = skb_unclone(skb, GFP_ATOMIC);
+		if (unlikely(err))
+			goto error;
+		skb_shinfo(skb)->gso_type |= SKB_GSO_GRE;
+		return skb;
+	} else if (skb->ip_summed == CHECKSUM_PARTIAL && gre_csum) {
+		err = skb_checksum_help(skb);
+		if (unlikely(err))
+			goto error;
+	} else if (skb->ip_summed != CHECKSUM_PARTIAL)
+		skb->ip_summed = CHECKSUM_NONE;
+
+	return skb;
+error:
+	kfree_skb(skb);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(gre_handle_offloads);
+
+static __sum16 check_checksum(struct sk_buff *skb)
+{
+	__sum16 csum = 0;
+
+	switch (skb->ip_summed) {
+	case CHECKSUM_COMPLETE:
+		csum = csum_fold(skb->csum);
+
+		if (!csum)
+			break;
+		/* Fall through. */
+
+	case CHECKSUM_NONE:
+		skb->csum = 0;
+		csum = __skb_checksum_complete(skb);
+		skb->ip_summed = CHECKSUM_COMPLETE;
+		break;
+	}
+
+	return csum;
+}
+
+static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
+			    bool *csum_err)
+{
+	unsigned int ip_hlen = ip_hdrlen(skb);
+	const struct gre_base_hdr *greh;
+	__be32 *options;
+	int hdr_len;
+
+	if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
+		return -EINVAL;
+
+	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
+	if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
+		return -EINVAL;
+
+	tpi->flags = gre_flags_to_tnl_flags(greh->flags);
+	hdr_len = ip_gre_calc_hlen(tpi->flags);
+
+	if (!pskb_may_pull(skb, hdr_len))
+		return -EINVAL;
+
+	greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
+	tpi->proto = greh->protocol;
+
+	options = (__be32 *)(greh + 1);
+	if (greh->flags & GRE_CSUM) {
+		if (check_checksum(skb)) {
+			*csum_err = true;
+			return -EINVAL;
+		}
+		options++;
+	}
+
+	if (greh->flags & GRE_KEY) {
+		tpi->key = *options;
+		options++;
+	} else
+		tpi->key = 0;
+
+	if (unlikely(greh->flags & GRE_SEQ)) {
+		tpi->seq = *options;
+		options++;
+	} else
+		tpi->seq = 0;
+
+	/* WCCP version 1 and 2 protocol decoding.
+	 * - Change protocol to IP
+	 * - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
+	 */
+	if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
+		tpi->proto = htons(ETH_P_IP);
+		if ((*(u8 *)options & 0xF0) != 0x40) {
+			hdr_len += 4;
+			if (!pskb_may_pull(skb, hdr_len))
+				return -EINVAL;
+		}
+	}
+
+	return iptunnel_pull_header(skb, hdr_len, tpi->proto);
+}
+
+static int gre_cisco_rcv(struct sk_buff *skb)
+{
+	struct tnl_ptk_info tpi;
+	int i;
+	bool csum_err = false;
+
+	if (parse_gre_header(skb, &tpi, &csum_err) < 0)
+		goto drop;
+
+	rcu_read_lock();
+	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
+		struct gre_cisco_protocol *proto;
+		int ret;
+
+		proto = rcu_dereference(gre_cisco_proto_list[i]);
+		if (!proto)
+			continue;
+		ret = proto->handler(skb, &tpi);
+		if (ret == PACKET_RCVD) {
+			rcu_read_unlock();
+			return 0;
+		}
+	}
+	rcu_read_unlock();
+
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+
+static void gre_cisco_err(struct sk_buff *skb, u32 info)
+{
+	/* All the routers (except for Linux) return only
+	 * 8 bytes of packet payload. It means, that precise relaying of
+	 * ICMP in the real Internet is absolutely infeasible.
+	 *
+	 * Moreover, Cisco "wise men" put GRE key to the third word
+	 * in GRE header. It makes impossible maintaining even soft
+	 * state for keyed
+	 * GRE tunnels with enabled checksum. Tell them "thank you".
+	 *
+	 * Well, I wonder, rfc1812 was written by Cisco employee,
+	 * what the hell these idiots break standards established
+	 * by themselves???
+	 */
+
+	const int type = icmp_hdr(skb)->type;
+	const int code = icmp_hdr(skb)->code;
+	struct tnl_ptk_info tpi;
+	bool csum_err = false;
+	int i;
+
+	if (parse_gre_header(skb, &tpi, &csum_err)) {
+		if (!csum_err)		/* ignore csum errors. */
+			return;
+	}
+
+	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
+		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
+				skb->dev->ifindex, 0, IPPROTO_GRE, 0);
+		return;
+	}
+	if (type == ICMP_REDIRECT) {
+		ipv4_redirect(skb, dev_net(skb->dev), skb->dev->ifindex, 0,
+				IPPROTO_GRE, 0);
+		return;
+	}
+
+	rcu_read_lock();
+	for (i = 0; i < GRE_IP_PROTO_MAX; i++) {
+		struct gre_cisco_protocol *proto;
+
+		proto = rcu_dereference(gre_cisco_proto_list[i]);
+		if (!proto)
+			continue;
+
+		if (proto->err_handler(skb, info, &tpi) == PACKET_RCVD)
+			goto out;
+
+	}
+out:
+	rcu_read_unlock();
+}
+
+static int gre_rcv(struct sk_buff *skb)
+{
+	const struct gre_protocol *proto;
+	u8 ver;
+	int ret;
+
+	if (!pskb_may_pull(skb, 12))
+		goto drop;
+
+	ver = skb->data[1]&0x7f;
+	if (ver >= GREPROTO_MAX)
+		goto drop;
+
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+	if (!proto || !proto->handler)
+		goto drop_unlock;
+	ret = proto->handler(skb);
+	rcu_read_unlock();
+	return ret;
+
+drop_unlock:
+	rcu_read_unlock();
+drop:
+	kfree_skb(skb);
+	return NET_RX_DROP;
+}
+
+static void gre_err(struct sk_buff *skb, u32 info)
+{
+	const struct gre_protocol *proto;
+	const struct iphdr *iph = (const struct iphdr *)skb->data;
+	u8 ver = skb->data[(iph->ihl<<2) + 1]&0x7f;
+
+	if (ver >= GREPROTO_MAX)
+		return;
+
+	rcu_read_lock();
+	proto = rcu_dereference(gre_proto[ver]);
+	if (proto && proto->err_handler)
+		proto->err_handler(skb, info);
+	rcu_read_unlock();
+}
+
+static const struct net_protocol net_gre_protocol = {
+	.handler     = gre_rcv,
+	.err_handler = gre_err,
+	.netns_ok    = 1,
+};
+
+static const struct gre_protocol ipgre_protocol = {
+	.handler     = gre_cisco_rcv,
+	.err_handler = gre_cisco_err,
+};
+
+int gre_cisco_register(struct gre_cisco_protocol *newp)
+{
+	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
+					    &gre_cisco_proto_list[newp->priority];
+
+	return (cmpxchg(proto, NULL, newp) == NULL) ? 0 : -EBUSY;
+}
+EXPORT_SYMBOL_GPL(gre_cisco_register);
+
+int gre_cisco_unregister(struct gre_cisco_protocol *del_proto)
+{
+	struct gre_cisco_protocol **proto = (struct gre_cisco_protocol **)
+					    &gre_cisco_proto_list[del_proto->priority];
+	int ret;
+
+	ret = (cmpxchg(proto, del_proto, NULL) == del_proto) ? 0 : -EINVAL;
+
+	if (ret)
+		return ret;
+
+	synchronize_net();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gre_cisco_unregister);
+
+static int __init gre_init(void)
+{
+	pr_info("GRE over IPv4 demultiplexor driver\n");
+
+	if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
+		pr_err("can't add protocol\n");
+		goto err;
+	}
+
+	if (gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0) {
+		pr_info("%s: can't add ipgre handler\n", __func__);
+		goto err_gre;
+	}
+
+	if (gre_offload_init()) {
+		pr_err("can't add protocol offload\n");
+		goto err_gso;
+	}
+
+	return 0;
+err_gso:
+	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
+err_gre:
+	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+err:
+	return -EAGAIN;
+}
+
+static void __exit gre_exit(void)
+{
+	gre_offload_exit();
+
+	gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
+	inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+}
+
+module_init(gre_init);
+module_exit(gre_exit);
+
+MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
+MODULE_AUTHOR("D. Kozlov (xeb@...l.ru)");
+MODULE_LICENSE("GPL");
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
new file mode 100644
index 0000000..a9d8cd2
--- /dev/null
+++ b/net/ipv4/gre_offload.c
@@ -0,0 +1,127 @@
+/*
+ *	IPV4 GSO/GRO offload support
+ *	Linux INET implementation
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *	GRE GSO support
+ */
+
+#include <linux/skbuff.h>
+#include <net/protocol.h>
+#include <net/gre.h>
+
+static int gre_gso_send_check(struct sk_buff *skb)
+{
+	if (!skb->encapsulation)
+		return -EINVAL;
+	return 0;
+}
+
+static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
+				       netdev_features_t features)
+{
+	struct sk_buff *segs = ERR_PTR(-EINVAL);
+	netdev_features_t enc_features;
+	int ghl = GRE_HEADER_SECTION;
+	struct gre_base_hdr *greh;
+	int mac_len = skb->mac_len;
+	__be16 protocol = skb->protocol;
+	int tnl_hlen;
+	bool csum;
+
+	if (unlikely(skb_shinfo(skb)->gso_type &
+				~(SKB_GSO_TCPV4 |
+				  SKB_GSO_TCPV6 |
+				  SKB_GSO_UDP |
+				  SKB_GSO_DODGY |
+				  SKB_GSO_TCP_ECN |
+				  SKB_GSO_GRE)))
+		goto out;
+
+	if (unlikely(!pskb_may_pull(skb, sizeof(*greh))))
+		goto out;
+
+	greh = (struct gre_base_hdr *)skb_transport_header(skb);
+
+	if (greh->flags & GRE_KEY)
+		ghl += GRE_HEADER_SECTION;
+	if (greh->flags & GRE_SEQ)
+		ghl += GRE_HEADER_SECTION;
+	if (greh->flags & GRE_CSUM) {
+		ghl += GRE_HEADER_SECTION;
+		csum = true;
+	} else
+		csum = false;
+
+	/* setup inner skb. */
+	skb->protocol = greh->protocol;
+	skb->encapsulation = 0;
+
+	if (unlikely(!pskb_may_pull(skb, ghl)))
+		goto out;
+
+	__skb_pull(skb, ghl);
+	skb_reset_mac_header(skb);
+	skb_set_network_header(skb, skb_inner_network_offset(skb));
+	skb->mac_len = skb_inner_network_offset(skb);
+
+	/* segment inner packet. */
+	enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
+	segs = skb_mac_gso_segment(skb, enc_features);
+	if (!segs || IS_ERR(segs))
+		goto out;
+
+	skb = segs;
+	tnl_hlen = skb_tnl_header_len(skb);
+	do {
+		__skb_push(skb, ghl);
+		if (csum) {
+			__be32 *pcsum;
+
+			if (skb_has_shared_frag(skb)) {
+				int err;
+
+				err = __skb_linearize(skb);
+				if (err) {
+					kfree_skb(segs);
+					segs = ERR_PTR(err);
+					goto out;
+				}
+			}
+
+			greh = (struct gre_base_hdr *)(skb->data);
+			pcsum = (__be32 *)(greh + 1);
+			*pcsum = 0;
+			*(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
+		}
+		__skb_push(skb, tnl_hlen - ghl);
+
+		skb_reset_mac_header(skb);
+		skb_set_network_header(skb, mac_len);
+		skb->mac_len = mac_len;
+		skb->protocol = protocol;
+	} while ((skb = skb->next));
+out:
+	return segs;
+}
+
+static const struct net_offload gre_offload = {
+	.callbacks = {
+		.gso_send_check = gre_gso_send_check,
+		.gso_segment = gre_gso_segment,
+	},
+};
+
+int __init gre_offload_init(void)
+{
+	return inet_add_offload(&gre_offload, IPPROTO_GRE);
+}
+
+void __exit gre_offload_exit(void)
+{
+	inet_del_offload(&gre_offload, IPPROTO_GRE);
+}
-- 
1.7.11.7

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