+/*
+ * Copyright (c) 2007-2013 Nicira, Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA
+ */
+
+#include <linux/module.h>
+#include <linux/if.h>
+#include <linux/if_tunnel.h>
+#include <linux/icmp.h>
+#include <linux/in.h>
+#include <linux/ip.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/spinlock.h>
+
+#include <net/gre.h>
+#include <net/icmp.h>
+#include <net/protocol.h>
+#include <net/route.h>
+#include <net/xfrm.h>
+
+#include "gso.h"
+
+static struct gre_cisco_protocol __rcu *gre_cisco_proto;
+
+static void gre_csum_fix(struct sk_buff *skb)
+{
+ struct gre_base_hdr *greh;
+ __be32 *options;
+ int gre_offset = skb_transport_offset(skb);
+
+ greh = (struct gre_base_hdr *)skb_transport_header(skb);
+ options = ((__be32 *)greh + 1);
+
+ *options = 0;
+ *(__sum16 *)options = csum_fold(skb_checksum(skb, gre_offset,
+ skb->len - gre_offset, 0));
+}
+
+struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum)
+{
+ int err;
+
+ skb_reset_inner_headers(skb);
+
+ if (skb_is_gso(skb)) {
+ if (gre_csum)
+ OVS_GSO_CB(skb)->fix_segment = gre_csum_fix;
+ } else {
+ if (skb->ip_summed == CHECKSUM_PARTIAL && gre_csum) {
+ err = skb_checksum_help(skb);
+ if (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);
+}
+
+static bool is_gre_gso(struct sk_buff *skb)
+{
+ return skb_is_gso(skb);
+}
+
+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 && !is_gre_gso(skb)) {
+ *ptr = 0;
+ *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
+ skb->len, 0));
+ }
+ }
+}
+
+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);
+ 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;
+ bool csum_err = false;
+ struct gre_cisco_protocol *proto;
+
+ rcu_read_lock();
+ proto = rcu_dereference(gre_cisco_proto);
+ if (!proto)
+ goto drop;
+
+ if (parse_gre_header(skb, &tpi, &csum_err) < 0)
+ goto drop;
+ proto->handler(skb, &tpi);
+ rcu_read_unlock();
+ return 0;
+
+drop:
+ rcu_read_unlock();
+ kfree_skb(skb);
+ return 0;
+}
+
+static const struct gre_protocol ipgre_protocol = {
+ .handler = gre_cisco_rcv,
+};
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
+static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
+
+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;
+}
+
+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_net();
+ return 0;
+}
+
+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 const struct net_protocol net_gre_protocol = {
+ .handler = gre_rcv,
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,32)
+ .netns_ok = 1,
+#endif
+};
+#endif
+
+static int gre_compat_init(void)
+{
+ int err;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
+ if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
+ pr_err("%s: cannot register gre protocol handler\n", __func__);
+ return -EAGAIN;
+ }
+#endif
+ err = gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO);
+ if (err) {
+ pr_warn("%s: cannot register gre_cisco protocol handler\n", __func__);
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
+ inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+#endif
+ }
+
+ return err;
+}
+
+static int gre_compat_exit(void)
+{
+ int ret;
+
+ ret = gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
+ if (ret)
+ return ret;
+
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
+ ret = inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
+ if (ret)
+ return ret;
+#endif
+ return 0;
+}
+
+int gre_cisco_register(struct gre_cisco_protocol *newp)
+{
+ int err;
+
+ err = gre_compat_init();
+ if (err)
+ return err;
+
+ return (cmpxchg((struct gre_cisco_protocol **)&gre_cisco_proto, NULL, newp) == NULL) ?
+ 0 : -EBUSY;
+}
+
+int gre_cisco_unregister(struct gre_cisco_protocol *proto)
+{
+ int ret;
+
+ ret = (cmpxchg((struct gre_cisco_protocol **)&gre_cisco_proto, proto, NULL) == proto) ?
+ 0 : -EINVAL;
+
+ if (ret)
+ return ret;
+
+ synchronize_net();
+ ret = gre_compat_exit();
+ return ret;
+}