gre: Allow multiple protocol listener for gre protocol.

Currently there is only one user is allowed to register for gre
protocol.  Following patch adds de-multiplexer.  So that multiple
modules can listen on gre protocol e.g. kernel gre devices and ovs.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 267 insertions, 151 deletions

diff --git a/include/net/gre.h b/include/net/gre.h
index 9f03a390c826..c6ea0c72c605 100644
--- a/include/net/gre.h
+++ b/include/net/gre.h
@@ -7,6 +7,7 @@
 #define GREPROTO_CISCO          0
 #define GREPROTO_PPTP           1
 #define GREPROTO_MAX            2
+#define GRE_IP_PROTO_MAX        2
 
 struct gre_protocol {
         int  (*handler)(struct sk_buff *skb);
@@ -22,6 +23,29 @@ struct gre_base_hdr {
 int gre_add_protocol(const struct gre_protocol *proto, u8 version);
 int gre_del_protocol(const struct gre_protocol *proto, u8 version);
 
+struct gre_cisco_protocol {
+        int (*handler)(struct sk_buff *skb, const struct tnl_ptk_info *tpi);
+        int (*err_handler)(struct sk_buff *skb, u32 info,
+                           const struct tnl_ptk_info *tpi);
+        u8 priority;
+};
+
+int gre_cisco_register(struct gre_cisco_protocol *proto);
+int gre_cisco_unregister(struct gre_cisco_protocol *proto);
+
+static inline int ip_gre_calc_hlen(__be16 o_flags)
+{
+        int addend = 4;
+
+        if (o_flags&TUNNEL_CSUM)
+                addend += 4;
+        if (o_flags&TUNNEL_KEY)
+                addend += 4;
+        if (o_flags&TUNNEL_SEQ)
+                addend += 4;
+        return addend;
+}
+
 static inline __be16 gre_flags_to_tnl_flags(__be16 flags)
 {
         __be16 tflags = 0;
diff --git a/net/ipv4/gre.c b/net/ipv4/gre.c
index 1e294d510ac3..8b9a373890ab 100644
--- a/net/ipv4/gre.c
+++ b/net/ipv4/gre.c
@@ -13,6 +13,8 @@
 #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>
@@ -24,8 +26,12 @@
 #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)
 {
@@ -55,6 +61,173 @@ int gre_del_protocol(const struct gre_protocol *proto, u8 version)
 }
 EXPORT_SYMBOL_GPL(gre_del_protocol);
 
+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 0;
+}
+
+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;
@@ -206,27 +379,68 @@ static const struct net_offload gre_offload = {
         },
 };
 
+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");
-                return -EAGAIN;
+                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");
-                inet_del_protocol(&net_gre_protocol, IPPROTO_GRE);
-                return -EAGAIN;
+                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);
 }
 
@@ -236,4 +450,3 @@ module_exit(gre_exit);
 MODULE_DESCRIPTION("GRE over IPv4 demultiplexer driver");
 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 MODULE_LICENSE("GPL");
-
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index a982657d05e7..19863a81cea1 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -121,103 +121,8 @@ static int ipgre_tunnel_init(struct net_device *dev);
 static int ipgre_net_id __read_mostly;
 static int gre_tap_net_id __read_mostly;
 
-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 ip_gre_calc_hlen(__be16 o_flags)
-{
-        int addend = 4;
-
-        if (o_flags&TUNNEL_CSUM)
-                addend += 4;
-        if (o_flags&TUNNEL_KEY)
-                addend += 4;
-        if (o_flags&TUNNEL_SEQ)
-                addend += 4;
-        return addend;
-}
-
-static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
-                            bool *csum_err, int *hdr_len)
-{
-        unsigned int ip_hlen = ip_hdrlen(skb);
-        const struct gre_base_hdr *greh;
-        __be32 *options;
-
-        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 0;
-}
-
-static void ipgre_err(struct sk_buff *skb, u32 info)
+static int ipgre_err(struct sk_buff *skb, u32 info,
+                     const struct tnl_ptk_info *tpi)
 {
 
         /* All the routers (except for Linux) return only
@@ -239,26 +144,18 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
         const int type = icmp_hdr(skb)->type;
         const int code = icmp_hdr(skb)->code;
         struct ip_tunnel *t;
-        struct tnl_ptk_info tpi;
-        int hdr_len;
-        bool csum_err = false;
-
-        if (parse_gre_header(skb, &tpi, &csum_err, &hdr_len)) {
-                if (!csum_err)          /* ignore csum errors. */
-                        return;
-        }
 
         switch (type) {
         default:
         case ICMP_PARAMETERPROB:
-                return;
+                return PACKET_RCVD;
 
         case ICMP_DEST_UNREACH:
                 switch (code) {
                 case ICMP_SR_FAILED:
                 case ICMP_PORT_UNREACH:
                         /* Impossible event. */
-                        return;
+                        return PACKET_RCVD;
                 default:
                         /* All others are translated to HOST_UNREACH.
                            rfc2003 contains "deep thoughts" about NET_UNREACH,
@@ -269,79 +166,61 @@ static void ipgre_err(struct sk_buff *skb, u32 info)
                 break;
         case ICMP_TIME_EXCEEDED:
                 if (code != ICMP_EXC_TTL)
-                        return;
+                        return PACKET_RCVD;
                 break;
 
         case ICMP_REDIRECT:
                 break;
         }
 
-        if (tpi.proto == htons(ETH_P_TEB))
+        if (tpi->proto == htons(ETH_P_TEB))
                 itn = net_generic(net, gre_tap_net_id);
         else
                 itn = net_generic(net, ipgre_net_id);
 
         iph = (const struct iphdr *)skb->data;
-        t = ip_tunnel_lookup(itn, skb->dev->ifindex, tpi.flags,
-                             iph->daddr, iph->saddr, tpi.key);
+        t = ip_tunnel_lookup(itn, skb->dev->ifindex, tpi->flags,
+                             iph->daddr, iph->saddr, tpi->key);
 
         if (t == NULL)
-                return;
+                return PACKET_REJECT;
 
-        if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
-                ipv4_update_pmtu(skb, dev_net(skb->dev), info,
-                                 t->parms.link, 0, IPPROTO_GRE, 0);
-                return;
-        }
-        if (type == ICMP_REDIRECT) {
-                ipv4_redirect(skb, dev_net(skb->dev), t->parms.link, 0,
-                              IPPROTO_GRE, 0);
-                return;
-        }
         if (t->parms.iph.daddr == 0 ||
             ipv4_is_multicast(t->parms.iph.daddr))
-                return;
+                return PACKET_RCVD;
 
         if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
-                return;
+                return PACKET_RCVD;
 
         if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
                 t->err_count++;
         else
                 t->err_count = 1;
         t->err_time = jiffies;
+        return PACKET_RCVD;
 }
 
-static int ipgre_rcv(struct sk_buff *skb)
+static int ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi)
 {
         struct net *net = dev_net(skb->dev);
         struct ip_tunnel_net *itn;
         const struct iphdr *iph;
         struct ip_tunnel *tunnel;
-        struct tnl_ptk_info tpi;
-        int hdr_len;
-        bool csum_err = false;
-
-        if (parse_gre_header(skb, &tpi, &csum_err, &hdr_len) < 0)
-                goto drop;
 
-        if (tpi.proto == htons(ETH_P_TEB))
+        if (tpi->proto == htons(ETH_P_TEB))
                 itn = net_generic(net, gre_tap_net_id);
         else
                 itn = net_generic(net, ipgre_net_id);
 
         iph = ip_hdr(skb);
-        tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, tpi.flags,
-                                  iph->saddr, iph->daddr, tpi.key);
+        tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, tpi->flags,
+                                  iph->saddr, iph->daddr, tpi->key);
 
         if (tunnel) {
-                ip_tunnel_rcv(tunnel, skb, &tpi, log_ecn_error);
-                return 0;
+                ip_tunnel_rcv(tunnel, skb, tpi, log_ecn_error);
+                return PACKET_RCVD;
         }
-        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
-drop:
-        kfree_skb(skb);
-        return 0;
+        return PACKET_REJECT;
 }
 
 static struct sk_buff *handle_offloads(struct ip_tunnel *tunnel, struct sk_buff *skb)
@@ -708,9 +587,10 @@ static int ipgre_tunnel_init(struct net_device *dev)
         return ip_tunnel_init(dev);
 }
 
-static const struct gre_protocol ipgre_protocol = {
-        .handler     = ipgre_rcv,
-        .err_handler = ipgre_err,
+static struct gre_cisco_protocol ipgre_protocol = {
+        .handler        = ipgre_rcv,
+        .err_handler    = ipgre_err,
+        .priority       = 0,
 };
 
 static int __net_init ipgre_init_net(struct net *net)
@@ -978,7 +858,7 @@ static int __init ipgre_init(void)
         if (err < 0)
                 goto pnet_tap_faied;
 
-        err = gre_add_protocol(&ipgre_protocol, GREPROTO_CISCO);
+        err = gre_cisco_register(&ipgre_protocol);
         if (err < 0) {
                 pr_info("%s: can't add protocol\n", __func__);
                 goto add_proto_failed;
@@ -997,7 +877,7 @@ static int __init ipgre_init(void)
 tap_ops_failed:
         rtnl_link_unregister(&ipgre_link_ops);
 rtnl_link_failed:
-        gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO);
+        gre_cisco_unregister(&ipgre_protocol);
 add_proto_failed:
         unregister_pernet_device(&ipgre_tap_net_ops);
 pnet_tap_faied:
@@ -1009,8 +889,7 @@ static void __exit ipgre_fini(void)
 {
         rtnl_link_unregister(&ipgre_tap_ops);
         rtnl_link_unregister(&ipgre_link_ops);
-        if (gre_del_protocol(&ipgre_protocol, GREPROTO_CISCO) < 0)
-                pr_info("%s: can't remove protocol\n", __func__);
+        gre_cisco_unregister(&ipgre_protocol);
         unregister_pernet_device(&ipgre_tap_net_ops);
         unregister_pernet_device(&ipgre_net_ops);
 }