Implement ipv6 udp hash4 like that in ipv4. The major difference is that
the hash value should be calculated with udp6_ehashfn(). Besides,
ipv4-mapped ipv6 address is handled before hash() and rehash(). Export
udp_ehashfn because now we use it in udpv6 rehash.

Core procedures of hash/unhash/rehash are same as ipv4, and udpv4 and
udpv6 share the same udptable, so some functions in ipv4 hash4 can also
be shared.

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Signed-off-by: Cambda Zhu <cambda@linux.alibaba.com>
Signed-off-by: Fred Chen <fred.cc@alibaba-inc.com>
Signed-off-by: Yubing Qiu <yubing.qiuyubing@alibaba-inc.com>
---
 include/net/udp.h |  2 +
 net/ipv4/udp.c    |  1 -
 net/ipv6/udp.c    | 96 ++++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 96 insertions(+), 3 deletions(-)

diff --git a/include/net/udp.h b/include/net/udp.h
index 6bfdd345e5f4b..2e9c1b4e3f392 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -302,6 +302,8 @@ static inline int udp_lib_hash(struct sock *sk)
 
 void udp_lib_unhash(struct sock *sk);
 void udp_lib_rehash(struct sock *sk, u16 new_hash, u16 new_hash4);
+u32 udp_ehashfn(const struct net *net, const __be32 laddr, const __u16 lport,
+		const __be32 faddr, const __be16 fport);
 
 static inline void udp_lib_close(struct sock *sk, long timeout)
 {
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 799e86c6ee840..102d0502c9985 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -410,7 +410,6 @@ static int compute_score(struct sock *sk, const struct net *net,
 	return score;
 }
 
-INDIRECT_CALLABLE_SCOPE
 u32 udp_ehashfn(const struct net *net, const __be32 laddr, const __u16 lport,
 		const __be32 faddr, const __be16 fport)
 {
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 1ea99d704e31a..64f13f258fca3 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -110,8 +110,17 @@ void udp_v6_rehash(struct sock *sk)
 	u16 new_hash = ipv6_portaddr_hash(sock_net(sk),
 					  &sk->sk_v6_rcv_saddr,
 					  inet_sk(sk)->inet_num);
+	u16 new_hash4;
 
-	udp_lib_rehash(sk, new_hash, 0); /* 4-tuple hash not implemented */
+	if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) {
+		new_hash4 = udp_ehashfn(sock_net(sk), sk->sk_rcv_saddr, sk->sk_num,
+					sk->sk_daddr, sk->sk_dport);
+	} else {
+		new_hash4 = udp6_ehashfn(sock_net(sk), &sk->sk_v6_rcv_saddr, sk->sk_num,
+					 &sk->sk_v6_daddr, sk->sk_dport);
+	}
+
+	udp_lib_rehash(sk, new_hash, new_hash4);
 }
 
 static int compute_score(struct sock *sk, const struct net *net,
@@ -216,6 +225,71 @@ static struct sock *udp6_lib_lookup2(const struct net *net,
 	return result;
 }
 
+#if IS_ENABLED(CONFIG_BASE_SMALL)
+static struct sock *udp6_lib_lookup4(const struct net *net,
+				     const struct in6_addr *saddr, __be16 sport,
+				     const struct in6_addr *daddr, unsigned int hnum,
+				     int dif, int sdif, struct udp_table *udptable)
+{
+	return NULL;
+}
+
+static void udp6_hash4(struct sock *sk)
+{
+}
+#else /* !CONFIG_BASE_SMALL */
+static struct sock *udp6_lib_lookup4(const struct net *net,
+				     const struct in6_addr *saddr, __be16 sport,
+				     const struct in6_addr *daddr, unsigned int hnum,
+				     int dif, int sdif, struct udp_table *udptable)
+{
+	const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
+	const struct hlist_nulls_node *node;
+	struct udp_hslot *hslot4;
+	unsigned int hash4, slot;
+	struct udp_sock *up;
+	struct sock *sk;
+
+	hash4 = udp6_ehashfn(net, daddr, hnum, saddr, sport);
+	slot = hash4 & udptable->mask;
+	hslot4 = &udptable->hash4[slot];
+
+begin:
+	udp_lrpa_for_each_entry_rcu(up, node, &hslot4->nulls_head) {
+		sk = (struct sock *)up;
+		if (inet6_match(net, sk, saddr, daddr, ports, dif, sdif))
+			return sk;
+	}
+
+	/* if the nulls value we got at the end of this lookup is not the expected one, we must
+	 * restart lookup. We probably met an item that was moved to another chain due to rehash.
+	 */
+	if (get_nulls_value(node) != slot)
+		goto begin;
+
+	return NULL;
+}
+
+static void udp6_hash4(struct sock *sk)
+{
+	struct net *net = sock_net(sk);
+	unsigned int hash;
+
+	if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) {
+		udp4_hash4(sk);
+		return;
+	}
+
+	if (sk_unhashed(sk) || ipv6_addr_any(&sk->sk_v6_rcv_saddr))
+		return;
+
+	hash = udp6_ehashfn(net, &sk->sk_v6_rcv_saddr, sk->sk_num,
+			    &sk->sk_v6_daddr, sk->sk_dport);
+
+	udp_lib_hash4(sk, hash);
+}
+#endif /* CONFIG_BASE_SMALL */
+
 /* rcu_read_lock() must be held */
 struct sock *__udp6_lib_lookup(const struct net *net,
 			       const struct in6_addr *saddr, __be16 sport,
@@ -231,6 +305,12 @@ struct sock *__udp6_lib_lookup(const struct net *net,
 	hash2 = ipv6_portaddr_hash(net, daddr, hnum);
 	hslot2 = udp_hashslot2(udptable, hash2);
 
+	if (udp_has_hash4(hslot2)) {
+		result = udp6_lib_lookup4(net, saddr, sport, daddr, hnum, dif, sdif, udptable);
+		if (result) /* udp6_lib_lookup4 return sk or NULL */
+			return result;
+	}
+
 	/* Lookup connected or non-wildcard sockets */
 	result = udp6_lib_lookup2(net, saddr, sport,
 				  daddr, hnum, dif, sdif,
@@ -1166,6 +1246,18 @@ static int udpv6_pre_connect(struct sock *sk, struct sockaddr *uaddr,
 	return BPF_CGROUP_RUN_PROG_INET6_CONNECT_LOCK(sk, uaddr, &addr_len);
 }
 
+static int udpv6_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	int res;
+
+	lock_sock(sk);
+	res = __ip6_datagram_connect(sk, uaddr, addr_len);
+	if (!res)
+		udp6_hash4(sk);
+	release_sock(sk);
+	return res;
+}
+
 /**
  *	udp6_hwcsum_outgoing  -  handle outgoing HW checksumming
  *	@sk:	socket we are sending on
@@ -1761,7 +1853,7 @@ struct proto udpv6_prot = {
 	.owner			= THIS_MODULE,
 	.close			= udp_lib_close,
 	.pre_connect		= udpv6_pre_connect,
-	.connect		= ip6_datagram_connect,
+	.connect		= udpv6_connect,
 	.disconnect		= udp_disconnect,
 	.ioctl			= udp_ioctl,
 	.init			= udpv6_init_sock,
-- 
2.32.0.3.g01195cf9f

Hi Philo,

kernel test robot noticed the following build errors:

[auto build test ERROR on net-next/main]

url:    https://github.com/intel-lab-lkp/linux/commits/Philo-Lu/net-udp-Add-a-new-struct-for-hash2-slot/20241105-201454
base:   net-next/main
patch link:    https://lore.kernel.org/r/20241105121225.12513-5-lulie%40linux.alibaba.com
patch subject: [PATCH v7 net-next 4/4] ipv6/udp: Add 4-tuple hash for connected socket
config: arc-randconfig-002-20241106 (https://download.01.org/0day-ci/archive/20241106/202411061155.g9trZ6rZ-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241106/202411061155.g9trZ6rZ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411061155.g9trZ6rZ-lkp@intel.com/

All errors (new ones prefixed by >>, old ones prefixed by <<):

>> ERROR: modpost: "udp_lib_hash4" [net/ipv6/ipv6.ko] undefined!
>> ERROR: modpost: "udp_ehashfn" [net/ipv6/ipv6.ko] undefined!
>> ERROR: modpost: "udp4_hash4" [net/ipv6/ipv6.ko] undefined!

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Sorry for missed EXPORT_SYMBOL()s that break ipv6.ko building. Will add 
for the shared functions including udp_ehashfn(), udp_lib_hash4(), and 
udp4_hash4().

-- 
Philo