ipv6: prepare headers for ipv6_stub removal

In preparation for dropping ipv6_stub and converting its users to direct
function calls, introduce static inline dummy functions and fallback
macros in the IPv6 networking headers. In addition, introduce checks on
fib6_nh_init(), ip6_dst_lookup_flow() and ip6_fragment() to avoid a
crash due to ipv6.disable=1 set during booting. The other functions are
safe as they cannot be called with ipv6.disable=1 set.

These fallbacks ensure that when CONFIG_IPV6 is completely disabled,
there are no compiling or linking errors due to code paths not guarded
by preprocessor macro IS_ENABLED(CONFIG_IPV6).

In addition, export ndisc_send_na(), ip6_route_input() and
ip6_fragment().

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Tested-by: Ricardo B. Marlière <rbm@suse.com>
Link: https://patch.msgid.link/20260325120928.15848-6-fmancera@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 10f30d158340e3e76fe00be1ac11b4d3c54f0dbf..20e1231262d6950669ce51b35fcafaf62093193b 100644 (file)
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -486,11 +486,30 @@ void rt6_get_prefsrc(const struct rt6_info *rt, struct in6_addr *addr)
        rcu_read_unlock();
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
 int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
                 struct fib6_config *cfg, gfp_t gfp_flags,
                 struct netlink_ext_ack *extack);
 void fib6_nh_release(struct fib6_nh *fib6_nh);
 void fib6_nh_release_dsts(struct fib6_nh *fib6_nh);
+#else
+static inline int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
+                              struct fib6_config *cfg, gfp_t gfp_flags,
+                              struct netlink_ext_ack *extack)
+{
+       NL_SET_ERR_MSG(extack, "IPv6 support not enabled in kernel");
+       return -EAFNOSUPPORT;
+}
+
+static inline void fib6_nh_release(struct fib6_nh *fib6_nh)
+{
+}
+
+static inline void fib6_nh_release_dsts(struct fib6_nh *fib6_nh)
+{
+}
+#endif
+
 
 int call_fib6_entry_notifiers(struct net *net,
                              enum fib_event_type event_type,
@@ -502,8 +521,15 @@ int call_fib6_multipath_entry_notifiers(struct net *net,
                                        unsigned int nsiblings,
                                        struct netlink_ext_ack *extack);
 int call_fib6_entry_notifiers_replace(struct net *net, struct fib6_info *rt);
+#if IS_ENABLED(CONFIG_IPV6)
 void fib6_rt_update(struct net *net, struct fib6_info *rt,
                    struct nl_info *info);
+#else
+static inline void fib6_rt_update(struct net *net, struct fib6_info *rt,
+                                 struct nl_info *info)
+{
+}
+#endif
 void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info,
                     unsigned int flags);
 
@@ -588,7 +614,13 @@ int fib6_tables_dump(struct net *net, struct notifier_block *nb,
                     struct netlink_ext_ack *extack);
 
 void fib6_update_sernum(struct net *net, struct fib6_info *rt);
+#if IS_ENABLED(CONFIG_IPV6)
 void fib6_update_sernum_upto_root(struct net *net, struct fib6_info *rt);
+#else
+static inline void fib6_update_sernum_upto_root(struct net *net, struct fib6_info *rt)
+{
+}
+#endif
 void fib6_update_sernum_stub(struct net *net, struct fib6_info *f6i);
 
 void fib6_metric_set(struct fib6_info *f6i, int metric, u32 val);

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 0c8eeb6abe7acbd7ca462806521756114731f0e9..09ffe0f13ce75288b1df156958f143d4e33c0e1f 100644 (file)
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -77,7 +77,14 @@ static inline bool rt6_qualify_for_ecmp(const struct fib6_info *f6i)
                f6i->fib6_nh->fib_nh_gw_family;
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
 void ip6_route_input(struct sk_buff *skb);
+#else
+static inline void ip6_route_input(struct sk_buff *skb)
+{
+}
+#endif
+
 struct dst_entry *ip6_route_input_lookup(struct net *net,
                                         struct net_device *dev,
                                         struct flowi6 *fl6,
@@ -119,7 +126,15 @@ int ipv6_route_ioctl(struct net *net, unsigned int cmd,
 int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
                  struct netlink_ext_ack *extack);
 int ip6_ins_rt(struct net *net, struct fib6_info *f6i);
+#if IS_ENABLED(CONFIG_IPV6)
 int ip6_del_rt(struct net *net, struct fib6_info *f6i, bool skip_notify);
+#else
+static inline int ip6_del_rt(struct net *net, struct fib6_info *f6i,
+                            bool skip_notify)
+{
+       return -EAFNOSUPPORT;
+}
+#endif
 
 void rt6_flush_exceptions(struct fib6_info *f6i);
 void rt6_age_exceptions(struct fib6_info *f6i, struct fib6_gc_args *gc_args,
@@ -270,8 +285,19 @@ static inline bool ipv6_anycast_destination(const struct dst_entry *dst,
        return __ipv6_anycast_destination(&rt->rt6i_dst, rt->rt6i_flags, daddr);
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
 int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
                 int (*output)(struct net *, struct sock *, struct sk_buff *));
+#else
+static inline int ip6_fragment(struct net *net, struct sock *sk,
+                              struct sk_buff *skb,
+                              int (*output)(struct net *, struct sock *,
+                                            struct sk_buff *))
+{
+       kfree_skb(skb);
+       return -EAFNOSUPPORT;
+}
+#endif
 
 /* Variant of dst_mtu() for IPv6 users */
 static inline u32 dst6_mtu(const struct dst_entry *dst)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 0958cc5c6ec381dd069ba52de6eb8e98fabb4652..f99f273341f0a512813585da79971dc8d78f4a13 100644 (file)
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -1044,8 +1044,18 @@ static inline struct sk_buff *ip6_finish_skb(struct sock *sk)
 
 int ip6_dst_lookup(struct net *net, struct sock *sk, struct dst_entry **dst,
                   struct flowi6 *fl6);
+#if IS_ENABLED(CONFIG_IPV6)
 struct dst_entry *ip6_dst_lookup_flow(struct net *net, const struct sock *sk, struct flowi6 *fl6,
                                      const struct in6_addr *final_dst);
+#else
+static inline struct dst_entry *ip6_dst_lookup_flow(struct net *net, const struct sock *sk,
+                                                   struct flowi6 *fl6,
+                                                   const struct in6_addr *final_dst)
+{
+       return ERR_PTR(-EAFNOSUPPORT);
+}
+#endif
+
 struct dst_entry *ip6_sk_dst_lookup_flow(struct sock *sk, struct flowi6 *fl6,
                                         const struct in6_addr *final_dst,
                                         bool connected);

diff --git a/include/net/ndisc.h b/include/net/ndisc.h
index d38783a2ce57834879011a95ad8d8f5fe87c33fd..19e2a177bd29876ef785e2a0841a75f04d091ef3 100644 (file)
--- a/include/net/ndisc.h
+++ b/include/net/ndisc.h
@@ -406,13 +406,17 @@ static inline void __ipv6_confirm_neigh_stub(struct net_device *dev,
 static inline struct neighbour *ip_neigh_gw6(struct net_device *dev,
                                             const void *addr)
 {
+#if IS_ENABLED(CONFIG_IPV6)
        struct neighbour *neigh;
 
        neigh = __ipv6_neigh_lookup_noref_stub(dev, addr);
        if (unlikely(!neigh))
-               neigh = __neigh_create(ipv6_stub->nd_tbl, addr, dev, false);
+               neigh = __neigh_create(&nd_tbl, addr, dev, false);
 
        return neigh;
+#else
+       return ERR_PTR(-EAFNOSUPPORT);
+#endif
 }
 
 int ndisc_init(void);

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 8e2a6b28cea7ae69099859b337c9044caf99e631..63abc4fddaee8e9cf2ad2ef0873c963eaea63247 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -873,6 +873,11 @@ int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
        __be32 frag_id;
        u8 *prevhdr, nexthdr = 0;
 
+       if (!ipv6_mod_enabled()) {
+               kfree_skb(skb);
+               return -EAFNOSUPPORT;
+       }
+
        err = ip6_find_1stfragopt(skb, &prevhdr);
        if (err < 0)
                goto fail;
@@ -1045,6 +1050,7 @@ fail:
        kfree_skb(skb);
        return err;
 }
+EXPORT_SYMBOL_GPL(ip6_fragment);
 
 static inline int ip6_rt_check(const struct rt6key *rt_key,
                               const struct in6_addr *fl_addr,
@@ -1256,6 +1262,8 @@ struct dst_entry *ip6_dst_lookup_flow(struct net *net, const struct sock *sk, st
        struct dst_entry *dst = NULL;
        int err;
 
+       if (!ipv6_mod_enabled())
+               return ERR_PTR(-EAFNOSUPPORT);
        err = ip6_dst_lookup_tail(net, sk, &dst, fl6);
        if (err)
                return ERR_PTR(err);

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index f6a5d8c73af9721741c11b543e5abeecdbf2079f..f76fb8a854523927ece41dc95d078fba3f9e5ae1 100644 (file)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -576,6 +576,7 @@ void ndisc_send_na(struct net_device *dev, const struct in6_addr *daddr,
 
        ndisc_send_skb(skb, daddr, src_addr);
 }
+EXPORT_SYMBOL_GPL(ndisc_send_na);
 
 static void ndisc_send_unsol_na(struct net_device *dev)
 {

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 08deb18dcc85da2dc61912c6e105d76d7b015b95..19eb6b70222785395b817f220faed4220c374a93 100644 (file)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2655,6 +2655,7 @@ void ip6_route_input(struct sk_buff *skb)
        skb_dst_set_noref(skb, ip6_route_input_lookup(net, skb->dev,
                                                      &fl6, skb, flags));
 }
+EXPORT_SYMBOL_GPL(ip6_route_input);
 
 INDIRECT_CALLABLE_SCOPE struct rt6_info *ip6_pol_route_output(struct net *net,
                                             struct fib6_table *table,
@@ -3585,6 +3586,11 @@ int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
        struct inet6_dev *idev = NULL;
        int err;
 
+       if (!ipv6_mod_enabled()) {
+               NL_SET_ERR_MSG(extack, "IPv6 support not enabled in kernel");
+               return -EAFNOSUPPORT;
+       }
+
        fib6_nh->fib_nh_family = AF_INET6;
 #ifdef CONFIG_IPV6_ROUTER_PREF
        fib6_nh->last_probe = jiffies;