ip_tunnel: Ops registration for secondary encap (fou, gue)

Instead of calling fou and gue functions directly from ip_tunnel
use ops for these that were previously registered. This patch adds the
logic to add and remove encapsulation operations for ip_tunnel,
and modified fou (and gue) to register with ip_tunnels.

This patch also addresses a circular dependency between ip_tunnel
and fou that was causing link errors when CONFIG_NET_IP_TUNNEL=y
and CONFIG_NET_FOU=m. References to fou an gue have been removed from
ip_tunnel.c

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 157 insertions, 47 deletions

diff --git a/include/net/fou.h b/include/net/fou.h
index 25b26ffcf1df..19b8a0c62a98 100644
--- a/include/net/fou.h
+++ b/include/net/fou.h
@@ -8,31 +8,12 @@
 #include <net/ip_tunnels.h>
 #include <net/udp.h>
 
+size_t fou_encap_hlen(struct ip_tunnel_encap *e);
+static size_t gue_encap_hlen(struct ip_tunnel_encap *e);
+
 int fou_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
                      u8 *protocol, struct flowi4 *fl4);
 int gue_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
                      u8 *protocol, struct flowi4 *fl4);
 
-static size_t fou_encap_hlen(struct ip_tunnel_encap *e)
-{
-        return sizeof(struct udphdr);
-}
-
-static size_t gue_encap_hlen(struct ip_tunnel_encap *e)
-{
-        size_t len;
-        bool need_priv = false;
-
-        len = sizeof(struct udphdr) + sizeof(struct guehdr);
-
-        if (e->flags & TUNNEL_ENCAP_FLAG_REMCSUM) {
-                len += GUE_PLEN_REMCSUM;
-                need_priv = true;
-        }
-
-        len += need_priv ? GUE_LEN_PRIV : 0;
-
-        return len;
-}
-
 #endif
diff --git a/include/net/ip_tunnels.h b/include/net/ip_tunnels.h
index 5bc6edeb7143..25a59eb388a6 100644
--- a/include/net/ip_tunnels.h
+++ b/include/net/ip_tunnels.h
@@ -117,6 +117,22 @@ struct ip_tunnel_net {
         struct hlist_head tunnels[IP_TNL_HASH_SIZE];
 };
 
+struct ip_tunnel_encap_ops {
+        size_t (*encap_hlen)(struct ip_tunnel_encap *e);
+        int (*build_header)(struct sk_buff *skb, struct ip_tunnel_encap *e,
+                            u8 *protocol, struct flowi4 *fl4);
+};
+
+#define MAX_IPTUN_ENCAP_OPS 8
+
+extern const struct ip_tunnel_encap_ops __rcu *
+                iptun_encaps[MAX_IPTUN_ENCAP_OPS];
+
+int ip_tunnel_encap_add_ops(const struct ip_tunnel_encap_ops *op,
+                            unsigned int num);
+int ip_tunnel_encap_del_ops(const struct ip_tunnel_encap_ops *op,
+                            unsigned int num);
+
 #ifdef CONFIG_INET
 
 int ip_tunnel_init(struct net_device *dev);
diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 740ae099a0d9..fe0907774ce8 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -668,6 +668,30 @@ static const struct genl_ops fou_nl_ops[] = {
         },
 };
 
+size_t fou_encap_hlen(struct ip_tunnel_encap *e)
+{
+        return sizeof(struct udphdr);
+}
+EXPORT_SYMBOL(fou_encap_hlen);
+
+size_t gue_encap_hlen(struct ip_tunnel_encap *e)
+{
+        size_t len;
+        bool need_priv = false;
+
+        len = sizeof(struct udphdr) + sizeof(struct guehdr);
+
+        if (e->flags & TUNNEL_ENCAP_FLAG_REMCSUM) {
+                len += GUE_PLEN_REMCSUM;
+                need_priv = true;
+        }
+
+        len += need_priv ? GUE_LEN_PRIV : 0;
+
+        return len;
+}
+EXPORT_SYMBOL(gue_encap_hlen);
+
 static void fou_build_udp(struct sk_buff *skb, struct ip_tunnel_encap *e,
                           struct flowi4 *fl4, u8 *protocol, __be16 sport)
 {
@@ -787,6 +811,57 @@ int gue_build_header(struct sk_buff *skb, struct ip_tunnel_encap *e,
 }
 EXPORT_SYMBOL(gue_build_header);
 
+#ifdef CONFIG_NET_FOU_IP_TUNNELS
+
+static const struct ip_tunnel_encap_ops __read_mostly fou_iptun_ops = {
+        .encap_hlen = fou_encap_hlen,
+        .build_header = fou_build_header,
+};
+
+static const struct ip_tunnel_encap_ops __read_mostly gue_iptun_ops = {
+        .encap_hlen = gue_encap_hlen,
+        .build_header = gue_build_header,
+};
+
+static int ip_tunnel_encap_add_fou_ops(void)
+{
+        int ret;
+
+        ret = ip_tunnel_encap_add_ops(&fou_iptun_ops, TUNNEL_ENCAP_FOU);
+        if (ret < 0) {
+                pr_err("can't add fou ops\n");
+                return ret;
+        }
+
+        ret = ip_tunnel_encap_add_ops(&gue_iptun_ops, TUNNEL_ENCAP_GUE);
+        if (ret < 0) {
+                pr_err("can't add gue ops\n");
+                ip_tunnel_encap_del_ops(&fou_iptun_ops, TUNNEL_ENCAP_FOU);
+                return ret;
+        }
+
+        return 0;
+}
+
+static void ip_tunnel_encap_del_fou_ops(void)
+{
+        ip_tunnel_encap_del_ops(&fou_iptun_ops, TUNNEL_ENCAP_FOU);
+        ip_tunnel_encap_del_ops(&gue_iptun_ops, TUNNEL_ENCAP_GUE);
+}
+
+#else
+
+static int ip_tunnel_encap_add_fou_ops(void)
+{
+        return 0;
+}
+
+static int ip_tunnel_encap_del_fou_ops(void)
+{
+}
+
+#endif
+
 static int __init fou_init(void)
 {
         int ret;
@@ -794,6 +869,14 @@ static int __init fou_init(void)
         ret = genl_register_family_with_ops(&fou_nl_family,
                                             fou_nl_ops);
 
+        if (ret < 0)
+                goto exit;
+
+        ret = ip_tunnel_encap_add_fou_ops();
+        if (ret < 0)
+                genl_unregister_family(&fou_nl_family);
+
+exit:
         return ret;
 }
 
@@ -801,6 +884,8 @@ static void __exit fou_fini(void)
 {
         struct fou *fou, *next;
 
+        ip_tunnel_encap_del_fou_ops();
+
         genl_unregister_family(&fou_nl_family);
 
         /* Close all the FOU sockets */
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index c3587e1c8b82..63e745aadab6 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -57,10 +57,6 @@
 #include <net/rtnetlink.h>
 #include <net/udp.h>
 
-#if IS_ENABLED(CONFIG_NET_FOU)
-#include <net/fou.h>
-#endif
-
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
 #include <net/ip6_fib.h>
@@ -494,19 +490,50 @@ EXPORT_SYMBOL_GPL(ip_tunnel_rcv);
 
 static int ip_encap_hlen(struct ip_tunnel_encap *e)
 {
-        switch (e->type) {
-        case TUNNEL_ENCAP_NONE:
+        const struct ip_tunnel_encap_ops *ops;
+        int hlen = -EINVAL;
+
+        if (e->type == TUNNEL_ENCAP_NONE)
                 return 0;
-#if IS_ENABLED(CONFIG_NET_FOU)
-        case TUNNEL_ENCAP_FOU:
-                return fou_encap_hlen(e);
-        case TUNNEL_ENCAP_GUE:
-                return gue_encap_hlen(e);
-#endif
-        default:
+
+        if (e->type >= MAX_IPTUN_ENCAP_OPS)
                 return -EINVAL;
-        }
+
+        rcu_read_lock();
+        ops = rcu_dereference(iptun_encaps[e->type]);
+        if (likely(ops && ops->encap_hlen))
+                hlen = ops->encap_hlen(e);
+        rcu_read_unlock();
+
+        return hlen;
+}
+
+const struct ip_tunnel_encap_ops __rcu *
+                iptun_encaps[MAX_IPTUN_ENCAP_OPS] __read_mostly;
+
+int ip_tunnel_encap_add_ops(const struct ip_tunnel_encap_ops *ops,
+                            unsigned int num)
+{
+        return !cmpxchg((const struct ip_tunnel_encap_ops **)
+                        &iptun_encaps[num],
+                        NULL, ops) ? 0 : -1;
 }
+EXPORT_SYMBOL(ip_tunnel_encap_add_ops);
+
+int ip_tunnel_encap_del_ops(const struct ip_tunnel_encap_ops *ops,
+                            unsigned int num)
+{
+        int ret;
+
+        ret = (cmpxchg((const struct ip_tunnel_encap_ops **)
+                       &iptun_encaps[num],
+                       ops, NULL) == ops) ? 0 : -1;
+
+        synchronize_net();
+
+        return ret;
+}
+EXPORT_SYMBOL(ip_tunnel_encap_del_ops);
 
 int ip_tunnel_encap_setup(struct ip_tunnel *t,
                           struct ip_tunnel_encap *ipencap)
@@ -534,18 +561,19 @@ EXPORT_SYMBOL_GPL(ip_tunnel_encap_setup);
 int ip_tunnel_encap(struct sk_buff *skb, struct ip_tunnel *t,
                     u8 *protocol, struct flowi4 *fl4)
 {
-        switch (t->encap.type) {
-        case TUNNEL_ENCAP_NONE:
+        const struct ip_tunnel_encap_ops *ops;
+        int ret = -EINVAL;
+
+        if (t->encap.type == TUNNEL_ENCAP_NONE)
                 return 0;
-#if IS_ENABLED(CONFIG_NET_FOU)
-        case TUNNEL_ENCAP_FOU:
-                return fou_build_header(skb, &t->encap, protocol, fl4);
-        case TUNNEL_ENCAP_GUE:
-                return gue_build_header(skb, &t->encap, protocol, fl4);
-#endif
-        default:
-                return -EINVAL;
-        }
+
+        rcu_read_lock();
+        ops = rcu_dereference(iptun_encaps[t->encap.type]);
+        if (likely(ops && ops->build_header))
+                ret = ops->build_header(skb, &t->encap, protocol, fl4);
+        rcu_read_unlock();
+
+        return ret;
 }
 EXPORT_SYMBOL(ip_tunnel_encap);