Re: [PATCH net v2] ipv6: socket SO_BINDTODEVICE lookup routing fail without IPv6 rule.

["Shiming Cheng (成诗明)" <Shiming.Cheng@mediatek.com>]

Hi David

Test cases will be provided later,  below are the corresponding IP rule
configurations for IPv4 and IPv6 that i provided, as well as the
differences in ping results, the IPv4 result passed, but the IPv6
result failed, after adding this patch, the IPv6 result passed.

Thanks

bind out interface ccmni2 address:
ccmni2    Link encap:UNSPEC
          inet addr:10.233.33.169  Mask:255.0.0.0
          inet6 addr: fe80::1817:1da4:19a1:dc42/64 Scope: Link
          inet6 addr: 2409:8900:26f3:2541:1817:1da4:19a1:dc42/64 Scope:

1.There is no ip rule for ccmni2 and also pass.
k6991v1_64:/ # ip rule list
0:      from all lookup local
10000:  from all fwmark 0xc0000/0xd0000 lookup legacy_system
11000:  from all iif lo oif dummy0 uidrange 0-0 lookup dummy0
11000:  from all iif lo oif ccmni1 uidrange 0-0 lookup ccmni1
16000:  from all fwmark 0x10063/0x1ffff iif lo lookup local_network
16000:  from all fwmark 0xd0071/0xdffff iif lo lookup ccmni1
17000:  from all iif lo oif dummy0 lookup dummy0
17000:  from all fwmark 0xc0000/0xc0000 iif lo oif ccmni1 lookup ccmni1
18000:  from all fwmark 0x0/0x10000 lookup legacy_system
19000:  from all fwmark 0x0/0x10000 lookup legacy_network
20000:  from all fwmark 0x0/0x10000 lookup local_network
32000:  from all unreachable
k6991v1_64:/ #
k6991v1_64:/ #
k6991v1_64:/ #
k6991v1_64:/ # ping -I ccmni2 8.8.8.8
PING 8.8.8.8 (8.8.8.8) from 10.233.33.169 ccmni2: 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=50 time=179 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=50 time=74.3 ms
64 bytes from 8.8.8.8: icmp_seq=3 ttl=50 time=72.7 ms
64 bytes from 8.8.8.8: icmp_seq=4 ttl=50 time=67.1 ms
64 bytes from 8.8.8.8: icmp_seq=5 ttl=50 time=63.3 ms
64 bytes from 8.8.8.8: icmp_seq=6 ttl=50 time=90.8 ms
^C
--- 8.8.8.8 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5017ms
rtt min/avg/max/mdev = 63.323/91.253/179.082/40.213 ms



2.There is no ipv6 rule for ccmni2 and fail.
k6991v1_64:/ # ip -6 rule list
0:      from all lookup local
10000:  from all fwmark 0xc0000/0xd0000 lookup legacy_system
11000:  from all iif lo oif dummy0 uidrange 0-0 lookup dummy0
11000:  from all iif lo oif ccmni1 uidrange 0-0 lookup ccmni1
16000:  from all fwmark 0x10063/0x1ffff iif lo lookup local_network
16000:  from all fwmark 0xd0071/0xdffff iif lo lookup ccmni1
17000:  from all iif lo oif dummy0 lookup dummy0
17000:  from all fwmark 0xc0000/0xc0000 iif lo oif ccmni1 lookup ccmni1
18000:  from all fwmark 0x0/0x10000 lookup legacy_system
19000:  from all fwmark 0x0/0x10000 lookup legacy_network
20000:  from all fwmark 0x0/0x10000 lookup local_network
32000:  from all unreachable
k6991v1_64:/ # ping6 -I ccmni2 2001:4860:4860::8888
connect: Network is unreachable


3.After merging the submitted patch.
There is no ipv6 rule for ccmni2 and pass.

ccmni2    Link encap:UNSPEC
          inet addr:10.185.46.236  Mask:255.0.0.0
          inet6 addr: 2409:8900:24d9:404e:1817:25c4:e1c7:4e52/64 Scope:

k6897v1_64:/ # ip -6 rule list
0:      from all lookup local
10000:  from all fwmark 0xc0000/0xd0000 lookup legacy_system
11000:  from all iif lo oif dummy0 uidrange 0-0 lookup dummy0
11000:  from all iif lo oif ccmni1 uidrange 0-0 lookup ccmni1
16000:  from all fwmark 0x10063/0x1ffff iif lo lookup local_network
16000:  from all fwmark 0xd0070/0xdffff iif lo lookup ccmni1
17000:  from all iif lo oif dummy0 lookup dummy0
17000:  from all fwmark 0xc0000/0xc0000 iif lo oif ccmni1 lookup ccmni1
18000:  from all fwmark 0x0/0x10000 lookup legacy_system
19000:  from all fwmark 0x0/0x10000 lookup legacy_network
20000:  from all fwmark 0x0/0x10000 lookup local_network
32000:  from all unreachable
k6897v1_64:/ # ping6 -I ccmni2 2001:4860:4860::8888
PING 2001:4860:4860::8888(2001:4860:4860::8888) from
2409:8900:24d9:404e:1817:25c4:e1c7:4e52 ccmni2: 56 data bytes
64 bytes from 2001:4860:4860::8888: icmp_seq=1 ttl=51 time=167 ms
64 bytes from 2001:4860:4860::8888: icmp_seq=2 ttl=51 time=73.9 ms
64 bytes from 2001:4860:4860::8888: icmp_seq=3 ttl=51 time=101 ms
64 bytes from 2001:4860:4860::8888: icmp_seq=4 ttl=51 time=62.3 ms
^C
--- 2001:4860:4860::8888 ping statistics ---
5 packets transmitted, 4 received, 20% packet loss, time 4011ms


On Fri, 2025-01-03 at 13:43 +0800, Shiming Cheng wrote:
> When using socket IPv6 with SO_BINDTODEVICE, if IPv6 rule is not
> matched, it will return ENETUNREACH. In fact, IPv4 does not behave
> this way. IPv4 prioritizes looking up IP rules for routing and
> forwarding, if not matched it will use socket-bound out interface
> to send packets. The modification here is to make IPv6 behave the
> same as IPv4. If IP rule is not found, it will also use socket-bound
> out interface to send packts.
> 
> Fixes: 6f21c96a78b8 ("ipv6: enforce flowi6_oif usage in
> ip6_dst_lookup_tail()")
> Signed-off-by: Shiming Cheng <shiming.cheng@mediatek.com>
> ---
>  include/net/ip6_route.h |  2 ++
>  net/ipv6/ip6_output.c   |  7 ++++++-
>  net/ipv6/route.c        | 34 ++++++++++++++++++++++++++++++++++
>  3 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
> index 6dbdf60b342f..0625597def6f 100644
> --- a/include/net/ip6_route.h
> +++ b/include/net/ip6_route.h
> @@ -214,6 +214,8 @@ void rt6_multipath_rebalance(struct fib6_info
> *f6i);
>  
>  void rt6_uncached_list_add(struct rt6_info *rt);
>  void rt6_uncached_list_del(struct rt6_info *rt);
> +struct rt6_info *ip6_create_rt_oif_rcu(struct net *net, const struct
> sock *sk,
> +		struct flowi6 *fl6, int flags);
>  
>  static inline const struct rt6_info *skb_rt6_info(const struct
> sk_buff *skb)
>  {
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index f7b4608bb316..95728c8921cb 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1156,8 +1156,13 @@ static int ip6_dst_lookup_tail(struct net
> *net, const struct sock *sk,
>  		*dst = ip6_route_output_flags(net, sk, fl6, flags);
>  
>  	err = (*dst)->error;
> -	if (err)
> +	if (err && (flags & RT6_LOOKUP_F_IFACE)) {
> +		*dst = (struct dst_entry *)ip6_create_rt_oif_rcu(net,
> sk, fl6, flags);
> +		if (!*dst)
> +			goto out_err_release;
> +	} else if (err) {
>  		goto out_err_release;
> +	}
>  
>  #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
>  	/*
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 67ff16c04718..7d7450fab44f 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1214,6 +1214,40 @@ static struct rt6_info
> *ip6_create_rt_rcu(const struct fib6_result *res)
>  	return nrt;
>  }
>  
> +struct rt6_info *ip6_create_rt_oif_rcu(struct net *net, const struct
> sock *sk,
> +				       struct flowi6 *fl6, int flags)
> +{
> +	struct rt6_info *rt;
> +	unsigned int prefs;
> +	int err;
> +	struct net_device *dev = dev_get_by_index_rcu(net, fl6-
> >flowi6_oif);
> +
> +	if (!dev)
> +		return NULL;
> +	rt = ip6_dst_alloc(dev_net(dev), dev, flags);
> +
> +	if (!rt)
> +		return NULL;
> +	rt->dst.error = 0;
> +	rt->dst.output = ip6_output;
> +	rt->dst.lastuse = jiffies;
> +	prefs = sk ? inet6_sk(sk)->srcprefs : 0;
> +	err = ipv6_dev_get_saddr(net, dev, &fl6->daddr, prefs, &fl6-
> >saddr);
> +
> +	if (err) {
> +		dst_release(&rt->dst);
> +		return NULL;
> +	}
> +	rt->rt6i_dst.addr = fl6->daddr;
> +	rt->rt6i_dst.plen = 128;
> +	rt->rt6i_src.addr = fl6->saddr;
> +	rt->rt6i_dst.plen = 128;
> +	rt->rt6i_idev = in6_dev_get(dev);
> +	rt->rt6i_flags = flags;
> +	return rt;
> +}
> +EXPORT_SYMBOL_GPL(ip6_create_rt_oif_rcu);
> +
>  INDIRECT_CALLABLE_SCOPE struct rt6_info *ip6_pol_route_lookup(struct
> net *net,
>  					     struct fib6_table *table,
>  					     struct flowi6 *fl6,