As IPv6 is built-in only, the ipv6_bpf_stub can be removed completely.

Convert all ipv6_bpf_stub usage to direct function calls instead. The
fallback functions introduced previously will prevent linkage errors
when CONFIG_IPV6 is disabled.

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Tested-by: Ricardo B. Marlière <rbm@suse.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
---
 include/net/ipv6.h       |  2 ++
 include/net/ipv6_stubs.h | 21 ----------------
 net/core/filter.c        | 54 ++++++++++++++++------------------------
 net/core/lwt_bpf.c       | 10 +++++---
 net/ipv6/af_inet6.c      | 13 ++--------
 5 files changed, 33 insertions(+), 67 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index f99f273341f0..d042afe7a245 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -1149,6 +1149,8 @@ void ipv6_local_rxpmtu(struct sock *sk, struct flowi6 *fl6, u32 mtu);
 void inet6_cleanup_sock(struct sock *sk);
 void inet6_sock_destruct(struct sock *sk);
 int inet6_release(struct socket *sock);
+int __inet6_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len,
+		 u32 flags);
 int inet6_bind(struct socket *sock, struct sockaddr_unsized *uaddr, int addr_len);
 int inet6_bind_sk(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len);
 int inet6_getname(struct socket *sock, struct sockaddr *uaddr,
diff --git a/include/net/ipv6_stubs.h b/include/net/ipv6_stubs.h
index 907681cecde8..dc708d9eca7a 100644
--- a/include/net/ipv6_stubs.h
+++ b/include/net/ipv6_stubs.h
@@ -77,25 +77,4 @@ struct ipv6_stub {
 			__u32 mark, struct ipv6_txoptions *opt, int tclass, u32 priority);
 };
 extern const struct ipv6_stub *ipv6_stub __read_mostly;
-
-/* A stub used by bpf helpers. Similarly ugly as ipv6_stub */
-struct ipv6_bpf_stub {
-	int (*inet6_bind)(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len,
-			  u32 flags);
-	struct sock *(*udp6_lib_lookup)(const struct net *net,
-					const struct in6_addr *saddr, __be16 sport,
-					const struct in6_addr *daddr, __be16 dport,
-					int dif, int sdif, struct sk_buff *skb);
-	int (*ipv6_setsockopt)(struct sock *sk, int level, int optname,
-			       sockptr_t optval, unsigned int optlen);
-	int (*ipv6_getsockopt)(struct sock *sk, int level, int optname,
-			       sockptr_t optval, sockptr_t optlen);
-	int (*ipv6_dev_get_saddr)(struct net *net,
-				  const struct net_device *dst_dev,
-				  const struct in6_addr *daddr,
-				  unsigned int prefs,
-				  struct in6_addr *saddr);
-};
-extern const struct ipv6_bpf_stub *ipv6_bpf_stub __read_mostly;
-
 #endif
diff --git a/net/core/filter.c b/net/core/filter.c
index c56821afaa0f..4b0c98f0d994 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -73,7 +73,6 @@
 #include <net/seg6.h>
 #include <net/seg6_local.h>
 #include <net/lwtunnel.h>
-#include <net/ipv6_stubs.h>
 #include <net/bpf_sk_storage.h>
 #include <net/transp_v6.h>
 #include <linux/btf_ids.h>
@@ -2279,7 +2278,7 @@ static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev,
 			.saddr	      = ip6h->saddr,
 		};
 
-		dst = ipv6_stub->ipv6_dst_lookup_flow(net, NULL, &fl6, NULL);
+		dst = ip6_dst_lookup_flow(net, NULL, &fl6, NULL);
 		if (IS_ERR(dst))
 			goto out_drop;
 
@@ -5577,12 +5576,12 @@ static int sol_ipv6_sockopt(struct sock *sk, int optname,
 	}
 
 	if (getopt)
-		return ipv6_bpf_stub->ipv6_getsockopt(sk, SOL_IPV6, optname,
-						      KERNEL_SOCKPTR(optval),
-						      KERNEL_SOCKPTR(optlen));
+		return do_ipv6_getsockopt(sk, SOL_IPV6, optname,
+					  KERNEL_SOCKPTR(optval),
+					  KERNEL_SOCKPTR(optlen));
 
-	return ipv6_bpf_stub->ipv6_setsockopt(sk, SOL_IPV6, optname,
-					      KERNEL_SOCKPTR(optval), *optlen);
+	return do_ipv6_setsockopt(sk, SOL_IPV6, optname,
+				  KERNEL_SOCKPTR(optval), *optlen);
 }
 
 static int __bpf_setsockopt(struct sock *sk, int level, int optname,
@@ -5981,9 +5980,6 @@ static const struct bpf_func_proto bpf_sock_ops_cb_flags_set_proto = {
 	.arg2_type	= ARG_ANYTHING,
 };
 
-const struct ipv6_bpf_stub *ipv6_bpf_stub __read_mostly;
-EXPORT_SYMBOL_GPL(ipv6_bpf_stub);
-
 BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
 	   int, addr_len)
 {
@@ -6007,11 +6003,9 @@ BPF_CALL_3(bpf_bind, struct bpf_sock_addr_kern *, ctx, struct sockaddr *, addr,
 			return err;
 		if (((struct sockaddr_in6 *)addr)->sin6_port == htons(0))
 			flags |= BIND_FORCE_ADDRESS_NO_PORT;
-		/* ipv6_bpf_stub cannot be NULL, since it's called from
-		 * bpf_cgroup_inet6_connect hook and ipv6 is already loaded
-		 */
-		return ipv6_bpf_stub->inet6_bind(sk, (struct sockaddr_unsized *)addr,
-						 addr_len, flags);
+
+		return __inet6_bind(sk, (struct sockaddr_unsized *)addr,
+				    addr_len, flags);
 #endif /* CONFIG_IPV6 */
 	}
 #endif /* CONFIG_INET */
@@ -6222,7 +6216,7 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		neigh = __ipv4_neigh_lookup_noref(dev,
 						  (__force u32)params->ipv4_dst);
 	else
-		neigh = __ipv6_neigh_lookup_noref_stub(dev, params->ipv6_dst);
+		neigh = __ipv6_neigh_lookup_noref(dev, params->ipv6_dst);
 
 	if (!neigh || !(READ_ONCE(neigh->nud_state) & NUD_VALID))
 		return BPF_FIB_LKUP_RET_NO_NEIGH;
@@ -6290,12 +6284,11 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 			params->tbid = 0;
 		}
 
-		tb = ipv6_stub->fib6_get_table(net, tbid);
+		tb = fib6_get_table(net, tbid);
 		if (unlikely(!tb))
 			return BPF_FIB_LKUP_RET_NOT_FWDED;
 
-		err = ipv6_stub->fib6_table_lookup(net, tb, oif, &fl6, &res,
-						   strict);
+		err = fib6_table_lookup(net, tb, oif, &fl6, &res, strict);
 	} else {
 		if (flags & BPF_FIB_LOOKUP_MARK)
 			fl6.flowi6_mark = params->mark;
@@ -6305,7 +6298,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		fl6.flowi6_tun_key.tun_id = 0;
 		fl6.flowi6_uid = sock_net_uid(net, NULL);
 
-		err = ipv6_stub->fib6_lookup(net, oif, &fl6, &res, strict);
+		err = fib6_lookup(net, oif, &fl6, &res, strict);
 	}
 
 	if (unlikely(err || IS_ERR_OR_NULL(res.f6i) ||
@@ -6326,11 +6319,11 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		return BPF_FIB_LKUP_RET_NOT_FWDED;
 	}
 
-	ipv6_stub->fib6_select_path(net, &res, &fl6, fl6.flowi6_oif,
-				    fl6.flowi6_oif != 0, NULL, strict);
+	fib6_select_path(net, &res, &fl6, fl6.flowi6_oif,
+			 fl6.flowi6_oif != 0, NULL, strict);
 
 	if (check_mtu) {
-		mtu = ipv6_stub->ip6_mtu_from_fib6(&res, dst, src);
+		mtu = ip6_mtu_from_fib6(&res, dst, src);
 		if (params->tot_len > mtu) {
 			params->mtu_result = mtu; /* union with tot_len */
 			return BPF_FIB_LKUP_RET_FRAG_NEEDED;
@@ -6351,9 +6344,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		if (res.f6i->fib6_prefsrc.plen) {
 			*src = res.f6i->fib6_prefsrc.addr;
 		} else {
-			err = ipv6_bpf_stub->ipv6_dev_get_saddr(net, dev,
-								&fl6.daddr, 0,
-								src);
+			err = ipv6_dev_get_saddr(net, dev, &fl6.daddr, 0, src);
 			if (err)
 				return BPF_FIB_LKUP_RET_NO_SRC_ADDR;
 		}
@@ -6365,7 +6356,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	/* xdp and cls_bpf programs are run in RCU-bh so rcu_read_lock_bh is
 	 * not needed here.
 	 */
-	neigh = __ipv6_neigh_lookup_noref_stub(dev, dst);
+	neigh = __ipv6_neigh_lookup_noref(dev, dst);
 	if (!neigh || !(READ_ONCE(neigh->nud_state) & NUD_VALID))
 		return BPF_FIB_LKUP_RET_NO_NEIGH;
 	memcpy(params->dmac, neigh->ha, ETH_ALEN);
@@ -6900,11 +6891,10 @@ static struct sock *sk_lookup(struct net *net, struct bpf_sock_tuple *tuple,
 					    src6, tuple->ipv6.sport,
 					    dst6, ntohs(tuple->ipv6.dport),
 					    dif, sdif, &refcounted);
-		else if (likely(ipv6_bpf_stub))
-			sk = ipv6_bpf_stub->udp6_lib_lookup(net,
-							    src6, tuple->ipv6.sport,
-							    dst6, tuple->ipv6.dport,
-							    dif, sdif, NULL);
+		else if (likely(ipv6_mod_enabled()))
+			sk = __udp6_lib_lookup(net, src6, tuple->ipv6.sport,
+					       dst6, tuple->ipv6.dport,
+					       dif, sdif, NULL);
 #endif
 	}
 
diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c
index 9f40be0c3e71..f71ef82a5f3d 100644
--- a/net/core/lwt_bpf.c
+++ b/net/core/lwt_bpf.c
@@ -13,7 +13,6 @@
 #include <net/gre.h>
 #include <net/ip.h>
 #include <net/ip6_route.h>
-#include <net/ipv6_stubs.h>
 
 struct bpf_lwt_prog {
 	struct bpf_prog *prog;
@@ -103,7 +102,12 @@ static int bpf_lwt_input_reroute(struct sk_buff *skb)
 		dev_put(dev);
 	} else if (skb->protocol == htons(ETH_P_IPV6)) {
 		skb_dst_drop(skb);
-		err = ipv6_stub->ipv6_route_input(skb);
+		if (IS_ENABLED(CONFIG_IPV6)) {
+			ip6_route_input(skb);
+			err = skb_dst(skb)->error;
+		} else {
+			err = -EAFNOSUPPORT;
+		}
 	} else {
 		err = -EAFNOSUPPORT;
 	}
@@ -233,7 +237,7 @@ static int bpf_lwt_xmit_reroute(struct sk_buff *skb)
 		fl6.daddr = iph6->daddr;
 		fl6.saddr = iph6->saddr;
 
-		dst = ipv6_stub->ipv6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
+		dst = ip6_dst_lookup_flow(net, skb->sk, &fl6, NULL);
 		if (IS_ERR(dst)) {
 			err = PTR_ERR(dst);
 			goto err;
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index bb29b29fdcfb..07ae6ea7743a 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -264,8 +264,8 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol,
 	goto out;
 }
 
-static int __inet6_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len,
-			u32 flags)
+int __inet6_bind(struct sock *sk, struct sockaddr_unsized *uaddr, int addr_len,
+		 u32 flags)
 {
 	struct sockaddr_in6 *addr = (struct sockaddr_in6 *)uaddr;
 	struct inet_sock *inet = inet_sk(sk);
@@ -1032,14 +1032,6 @@ static const struct ipv6_stub ipv6_stub_impl = {
 	.ip6_xmit = ip6_xmit,
 };
 
-static const struct ipv6_bpf_stub ipv6_bpf_stub_impl = {
-	.inet6_bind = __inet6_bind,
-	.udp6_lib_lookup = __udp6_lib_lookup,
-	.ipv6_setsockopt = do_ipv6_setsockopt,
-	.ipv6_getsockopt = do_ipv6_getsockopt,
-	.ipv6_dev_get_saddr = ipv6_dev_get_saddr,
-};
-
 static int __init inet6_init(void)
 {
 	struct list_head *r;
@@ -1199,7 +1191,6 @@ static int __init inet6_init(void)
 	/* ensure that ipv6 stubs are visible only after ipv6 is ready */
 	wmb();
 	ipv6_stub = &ipv6_stub_impl;
-	ipv6_bpf_stub = &ipv6_bpf_stub_impl;
 out:
 	return err;
 
-- 
2.53.0