Re: [PATCH v6 net-next 4/4] ipv6/udp: Add 4-tuple hash for connected socket

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Philo Lu <lulie@linux.alibaba.com>
Date: Fri, 1 Nov 2024 19:40:19 +0800
> On 2024/10/31 20:45, Philo Lu wrote:
> > 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().
> > 
> > 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>
> > ---
> >   net/ipv6/udp.c | 96 ++++++++++++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 94 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> > index 1ea99d704e31..64f13f258fca 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);
> 
> Just found udp_ehashfn() used here results in an build error of 
> undefined function.
> 
> I think the `ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)` branch can be 
> moved into udp_lib_rehash() to fix the issue. So in the worst case, we 
> need to calculate the newhash4 twice in ipv6 hash4 rehash, one in 
> udp_v6_rehash() and the other in udp_lib_rehash().

You can simply export udp_ehashfn().