Re: [PATCH net 1/2] ipv6: add ipv6_dev_find()

On Thu, Aug 6, 2020 at 10:03 PM David Ahern [off-list ref] wrote:

On 8/6/20 2:55 AM, Xin Long wrote:

quoted

On Thu, Aug 6, 2020 at 10:50 AM Hideaki Yoshifuji
[off-list ref] wrote:

quoted

Hi,

2020年8月4日(火) 0:35 Xin Long [off-list ref]:

quoted

This is to add an ip_dev_find like function for ipv6, used to find
the dev by saddr.

It will be used by TIPC protocol. So also export it.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 include/net/addrconf.h |  2 ++
 net/ipv6/addrconf.c    | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/include/net/addrconf.h b/include/net/addrconf.h
index 8418b7d..ba3f6c15 100644
--- a/include/net/addrconf.h
+++ b/include/net/addrconf.h

@@ -97,6 +97,8 @@ bool ipv6_chk_custom_prefix(const struct in6_addr *addr,

 int ipv6_chk_prefix(const struct in6_addr *addr, struct net_device *dev);

+struct net_device *ipv6_dev_find(struct net *net, const struct in6_addr *addr);
+

How do we handle link-local addresses?

This is what "if (!result)" branch meant to do:

+       if (!result) {
+               struct rt6_info *rt;
+
+               rt = rt6_lookup(net, addr, NULL, 0, NULL, 0);
+               if (rt) {
+                       dev = rt->dst.dev;
+                       ip6_rt_put(rt);
+               }
+       } else {
+               dev = result->idev->dev;
+       }

the stated purpose of this function is to find the netdevice to which an
address is attached. A route lookup should not be needed. Walking the
address hash list finds the address and hence the netdev or it does not.

Hi, David,
Sorry. it does. I misunderstood the code in __ip_dev_find().
I will delete the rt6_lookup() part from ipv6_dev_find().

Also for the compatibility, tipc part should change to:

@@ -741,10 +741,8 @@ static int tipc_udp_enable(struct net *net,

struct tipc_bearer *b,
                struct net_device *dev;

               dev = ipv6_dev_find(net, &local.ipv6);
               if (!dev)
                      ub->ifindex = dev->ifindex;

as when dev is not found from the hash list, it should fall back to
the old tipc code.

Ying, what do you think?