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* Copyright (c) 2007-2013 Nicira, Inc.
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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#include <linux/kconfig.h>
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#if IS_ENABLED(CONFIG_NET_IPGRE_DEMUX)
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#include <linux/module.h>
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#include <linux/if_tunnel.h>
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#include <linux/icmp.h>
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#include <linux/kernel.h>
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#include <linux/kmod.h>
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#include <linux/netdevice.h>
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#include <linux/skbuff.h>
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#include <linux/spinlock.h>
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#include <net/protocol.h>
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#include <net/route.h>
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static struct gre_cisco_protocol __rcu *gre_cisco_proto;
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static void gre_csum_fix(struct sk_buff *skb)
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struct gre_base_hdr *greh;
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int gre_offset = skb_transport_offset(skb);
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greh = (struct gre_base_hdr *)skb_transport_header(skb);
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options = ((__be32 *)greh + 1);
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*(__sum16 *)options = csum_fold(skb_checksum(skb, gre_offset,
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skb->len - gre_offset, 0));
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struct sk_buff *gre_handle_offloads(struct sk_buff *skb, bool gre_csum)
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skb_reset_inner_headers(skb);
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if (skb_is_gso(skb)) {
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OVS_GSO_CB(skb)->fix_segment = gre_csum_fix;
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if (skb->ip_summed == CHECKSUM_PARTIAL && gre_csum) {
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err = skb_checksum_help(skb);
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} else if (skb->ip_summed != CHECKSUM_PARTIAL)
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skb->ip_summed = CHECKSUM_NONE;
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static bool is_gre_gso(struct sk_buff *skb)
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return skb_is_gso(skb);
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void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
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struct gre_base_hdr *greh;
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__skb_push(skb, hdr_len);
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greh = (struct gre_base_hdr *)skb->data;
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greh->flags = tnl_flags_to_gre_flags(tpi->flags);
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greh->protocol = tpi->proto;
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if (tpi->flags & (TUNNEL_KEY | TUNNEL_CSUM | TUNNEL_SEQ)) {
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__be32 *ptr = (__be32 *)(((u8 *)greh) + hdr_len - 4);
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if (tpi->flags & TUNNEL_SEQ) {
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if (tpi->flags & TUNNEL_KEY) {
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if (tpi->flags & TUNNEL_CSUM && !is_gre_gso(skb)) {
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*(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
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static __sum16 check_checksum(struct sk_buff *skb)
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switch (skb->ip_summed) {
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case CHECKSUM_COMPLETE:
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csum = csum_fold(skb->csum);
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csum = __skb_checksum_complete(skb);
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skb->ip_summed = CHECKSUM_COMPLETE;
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static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
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unsigned int ip_hlen = ip_hdrlen(skb);
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struct gre_base_hdr *greh;
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if (unlikely(!pskb_may_pull(skb, sizeof(struct gre_base_hdr))))
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greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
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if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING)))
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tpi->flags = gre_flags_to_tnl_flags(greh->flags);
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hdr_len = ip_gre_calc_hlen(tpi->flags);
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if (!pskb_may_pull(skb, hdr_len))
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greh = (struct gre_base_hdr *)(skb_network_header(skb) + ip_hlen);
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tpi->proto = greh->protocol;
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options = (__be32 *)(greh + 1);
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if (greh->flags & GRE_CSUM) {
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if (check_checksum(skb)) {
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if (greh->flags & GRE_KEY) {
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if (unlikely(greh->flags & GRE_SEQ)) {
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/* WCCP version 1 and 2 protocol decoding.
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* - Change protocol to IP
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* - When dealing with WCCPv2, Skip extra 4 bytes in GRE header
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if (greh->flags == 0 && tpi->proto == htons(ETH_P_WCCP)) {
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tpi->proto = htons(ETH_P_IP);
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if ((*(u8 *)options & 0xF0) != 0x40) {
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if (!pskb_may_pull(skb, hdr_len))
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return iptunnel_pull_header(skb, hdr_len, tpi->proto);
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static int gre_cisco_rcv(struct sk_buff *skb)
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struct tnl_ptk_info tpi;
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bool csum_err = false;
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struct gre_cisco_protocol *proto;
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proto = rcu_dereference(gre_cisco_proto);
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if (parse_gre_header(skb, &tpi, &csum_err) < 0)
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proto->handler(skb, &tpi);
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static const struct gre_protocol ipgre_protocol = {
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.handler = gre_cisco_rcv,
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#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
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static const struct gre_protocol __rcu *gre_proto[GREPROTO_MAX] __read_mostly;
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int gre_add_protocol(const struct gre_protocol *proto, u8 version)
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if (version >= GREPROTO_MAX)
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return (cmpxchg((const struct gre_protocol **)&gre_proto[version], NULL, proto) == NULL) ?
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int gre_del_protocol(const struct gre_protocol *proto, u8 version)
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if (version >= GREPROTO_MAX)
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ret = (cmpxchg((const struct gre_protocol **)&gre_proto[version], proto, NULL) == proto) ?
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static int gre_rcv(struct sk_buff *skb)
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const struct gre_protocol *proto;
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if (!pskb_may_pull(skb, 12))
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ver = skb->data[1] & 0x7f;
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if (ver >= GREPROTO_MAX)
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proto = rcu_dereference(gre_proto[ver]);
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if (!proto || !proto->handler)
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ret = proto->handler(skb);
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static const struct net_protocol net_gre_protocol = {
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#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,32)
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static int gre_compat_init(void)
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#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
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if (inet_add_protocol(&net_gre_protocol, IPPROTO_GRE) < 0) {
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pr_err("%s: cannot register gre protocol handler\n", __func__);
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err = gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO);
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pr_warn("%s: cannot register gre_cisco protocol handler\n", __func__);
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#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
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inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
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static int gre_compat_exit(void)
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ret = gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
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#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,37)
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ret = inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
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int gre_cisco_register(struct gre_cisco_protocol *newp)
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err = gre_compat_init();
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return (cmpxchg((struct gre_cisco_protocol **)&gre_cisco_proto, NULL, newp) == NULL) ?
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int gre_cisco_unregister(struct gre_cisco_protocol *proto)
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ret = (cmpxchg((struct gre_cisco_protocol **)&gre_cisco_proto, proto, NULL) == proto) ?
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ret = gre_compat_exit();
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#endif /* CONFIG_NET_IPGRE_DEMUX */