We cannot make a direct call to nf_ip6_checksum() because that would
result in autoloading the 'ipv6' module because of symbol dependencies.
Therefore, define checksum indirection in nf_ipv6_ops where this really
belongs to.

For IPv4, we can indeed make a direct function call, which is faster,
given IPv4 is built-in in the networking code by default. Still,
CONFIG_INET=n and CONFIG_NETFILTER=y is possible, so define empty inline
stub for IPv4 in such case.

Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
 include/linux/netfilter.h               | 19 +++----------------
 include/linux/netfilter_ipv4.h          | 10 ++++++++++
 include/linux/netfilter_ipv6.h          |  2 ++
 net/bridge/netfilter/nf_tables_bridge.c |  7 -------
 net/ipv4/netfilter.c                    |  1 -
 net/ipv6/netfilter.c                    |  4 ++--
 net/netfilter/Makefile                  |  2 +-
 net/netfilter/utils.c                   | 26 ++++++++++++++++++++++++++
 8 files changed, 44 insertions(+), 27 deletions(-)
 create mode 100644 net/netfilter/utils.c

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 85a0b0d599e6..4c4d38ef1a76 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -311,8 +311,6 @@ struct nf_queue_entry;
 
 struct nf_afinfo {
        unsigned short  family;
-       __sum16         (*checksum)(struct sk_buff *skb, unsigned int hook,
-                                   unsigned int dataoff, u_int8_t protocol);
        __sum16         (*checksum_partial)(struct sk_buff *skb,
                                            unsigned int hook,
                                            unsigned int dataoff,
@@ -333,20 +331,9 @@ static inline const struct nf_afinfo 
*nf_get_afinfo(unsigned short family)
        return rcu_dereference(nf_afinfo[family]);
 }
 
-static inline __sum16
-nf_checksum(struct sk_buff *skb, unsigned int hook, unsigned int dataoff,
-           u_int8_t protocol, unsigned short family)
-{
-       const struct nf_afinfo *afinfo;
-       __sum16 csum = 0;
-
-       rcu_read_lock();
-       afinfo = nf_get_afinfo(family);
-       if (afinfo)
-               csum = afinfo->checksum(skb, hook, dataoff, protocol);
-       rcu_read_unlock();
-       return csum;
-}
+__sum16 nf_checksum(struct sk_buff *skb, unsigned int hook,
+                   unsigned int dataoff, u_int8_t protocol,
+                   unsigned short family);
 
 static inline __sum16
 nf_checksum_partial(struct sk_buff *skb, unsigned int hook,
diff --git a/include/linux/netfilter_ipv4.h b/include/linux/netfilter_ipv4.h
index 98c03b2462b5..c7deb78bac88 100644
--- a/include/linux/netfilter_ipv4.h
+++ b/include/linux/netfilter_ipv4.h
@@ -7,6 +7,16 @@
 #include <uapi/linux/netfilter_ipv4.h>
 
 int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned 
addr_type);
+
+#ifdef CONFIG_INET
 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
                       unsigned int dataoff, u_int8_t protocol);
+#else
+static inline __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
+                                    unsigned int dataoff, u_int8_t protocol)
+{
+       return 0;
+}
+#endif /* CONFIG_INET */
+
 #endif /*__LINUX_IP_NETFILTER_H*/
diff --git a/include/linux/netfilter_ipv6.h b/include/linux/netfilter_ipv6.h
index 47c6b04c28c0..b136101b5cde 100644
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -19,6 +19,8 @@ struct nf_ipv6_ops {
        void (*route_input)(struct sk_buff *skb);
        int (*fragment)(struct net *net, struct sock *sk, struct sk_buff *skb,
                        int (*output)(struct net *, struct sock *, struct 
sk_buff *));
+       __sum16 (*checksum)(struct sk_buff *skb, unsigned int hook,
+                           unsigned int dataoff, u_int8_t protocol);
 };
 
 #ifdef CONFIG_NETFILTER
diff --git a/net/bridge/netfilter/nf_tables_bridge.c 
b/net/bridge/netfilter/nf_tables_bridge.c
index 74260ffec74d..b850c17f02f5 100644
--- a/net/bridge/netfilter/nf_tables_bridge.c
+++ b/net/bridge/netfilter/nf_tables_bridge.c
@@ -106,12 +106,6 @@ static int nf_br_reroute(struct net *net, struct sk_buff 
*skb,
        return 0;
 }
 
-static __sum16 nf_br_checksum(struct sk_buff *skb, unsigned int hook,
-                             unsigned int dataoff, u_int8_t protocol)
-{
-       return 0;
-}
-
 static __sum16 nf_br_checksum_partial(struct sk_buff *skb, unsigned int hook,
                                      unsigned int dataoff, unsigned int len,
                                      u_int8_t protocol)
@@ -127,7 +121,6 @@ static int nf_br_route(struct net *net, struct dst_entry 
**dst,
 
 static const struct nf_afinfo nf_br_afinfo = {
        .family                 = AF_BRIDGE,
-       .checksum               = nf_br_checksum,
        .checksum_partial       = nf_br_checksum_partial,
        .route                  = nf_br_route,
        .saveroute              = nf_br_saveroute,
diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c
index c0cc6aa8cfaa..2f7ffefd2732 100644
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -188,7 +188,6 @@ static int nf_ip_route(struct net *net, struct dst_entry 
**dst,
 
 static const struct nf_afinfo nf_ip_afinfo = {
        .family                 = AF_INET,
-       .checksum               = nf_ip_checksum,
        .checksum_partial       = nf_ip_checksum_partial,
        .route                  = nf_ip_route,
        .saveroute              = nf_ip_saveroute,
diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index 39970e212ad5..db69c8af95aa 100644
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -192,12 +192,12 @@ static __sum16 nf_ip6_checksum_partial(struct sk_buff 
*skb, unsigned int hook,
 static const struct nf_ipv6_ops ipv6ops = {
        .chk_addr       = ipv6_chk_addr,
        .route_input    = ip6_route_input,
-       .fragment       = ip6_fragment
+       .fragment       = ip6_fragment,
+       .checksum       = nf_ip6_checksum,
 };
 
 static const struct nf_afinfo nf_ip6_afinfo = {
        .family                 = AF_INET6,
-       .checksum               = nf_ip6_checksum,
        .checksum_partial       = nf_ip6_checksum_partial,
        .route                  = nf_ip6_route,
        .saveroute              = nf_ip6_saveroute,
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 490a55e7166d..eec0c3b72926 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-netfilter-objs := core.o nf_log.o nf_queue.o nf_sockopt.o
+netfilter-objs := core.o nf_log.o nf_queue.o nf_sockopt.o utils.o
 
 nf_conntrack-y := nf_conntrack_core.o nf_conntrack_standalone.o 
nf_conntrack_expect.o nf_conntrack_helper.o nf_conntrack_proto.o 
nf_conntrack_l3proto_generic.o nf_conntrack_proto_generic.o 
nf_conntrack_proto_tcp.o nf_conntrack_proto_udp.o nf_conntrack_extend.o 
nf_conntrack_acct.o nf_conntrack_seqadj.o
 nf_conntrack-$(CONFIG_NF_CONNTRACK_TIMEOUT) += nf_conntrack_timeout.o
diff --git a/net/netfilter/utils.c b/net/netfilter/utils.c
new file mode 100644
index 000000000000..159a9cdcfe1e
--- /dev/null
+++ b/net/netfilter/utils.c
@@ -0,0 +1,26 @@
+#include <linux/kernel.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
+
+__sum16 nf_checksum(struct sk_buff *skb, unsigned int hook,
+                   unsigned int dataoff, u_int8_t protocol,
+                   unsigned short family)
+{
+       const struct nf_ipv6_ops *v6ops;
+       __sum16 csum = 0;
+
+       switch (family) {
+       case AF_INET:
+               csum = nf_ip_checksum(skb, hook, dataoff, protocol);
+               break;
+       case AF_INET6:
+               v6ops = rcu_dereference(nf_ipv6_ops);
+               if (v6ops)
+                       csum = v6ops->checksum(skb, hook, dataoff, protocol);
+               break;
+       }
+
+       return csum;
+}
+EXPORT_SYMBOL_GPL(nf_checksum);
-- 
2.11.0

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