Re: [PATCH net] ipv6: set fc_protocol with 0 when rtm_protocol is RTPROT_REDIRECT

[David Ahern <dsahern@gmail.com>]

On 7/30/17 9:31 PM, Xin Long wrote:
>> Did you look at removing this hunk from rt6_fill_node:
>>
>>         if (rt->rt6i_flags & RTF_DYNAMIC)
>>                 rtm->rtm_protocol = RTPROT_REDIRECT;
>>         else if (rt->rt6i_flags & RTF_ADDRCONF) {
>>                 if (rt->rt6i_flags & (RTF_DEFAULT | RTF_ROUTEINFO))
>>                         rtm->rtm_protocol = RTPROT_RA;
>>                 else
>>                         rtm->rtm_protocol = RTPROT_KERNEL;
>>         }
> The issue seems to affect "ip -6 route flush all" as well, not only cache
> since 'else if {}' also  causes rtm proto being different from rt6 proto.
> 
>>
>> And have rtm_protocol set properly on the route when it is installed?
> The codes not keeping rtm proto consistent with rt6 proto day 1,
> any idea on why it didn't use rt6 proto in kernel properly?

no, AFAIK it was just an oversight when the original code was written. I
do not know of any reason that would prevent properly setting the
rt6i_protocol in the route when it is allocated.

Something like this (not compiled, much less tested):

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4d30c96a819d..9a928839d247 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2347,6 +2347,7 @@ static void rt6_do_redirect(struct dst_entry *dst,
struct sock *sk, struct sk_bu
        if (!nrt)
                goto out;

+       nrt->rt6i_protocol = RTPROT_REDIRECT;
        nrt->rt6i_flags = RTF_GATEWAY|RTF_UP|RTF_DYNAMIC|RTF_CACHE;
        if (on_link)
                nrt->rt6i_flags &= ~RTF_GATEWAY;
@@ -2461,6 +2462,7 @@ static struct rt6_info *rt6_add_route_info(struct
net *net,
                .fc_dst_len     = prefixlen,
                .fc_flags       = RTF_GATEWAY | RTF_ADDRCONF |
RTF_ROUTEINFO |
                                  RTF_UP | RTF_PREF(pref),
+               .fc_protocol    = RTPROT_RA,
                .fc_nlinfo.portid = 0,
                .fc_nlinfo.nlh = NULL,
                .fc_nlinfo.nl_net = net,
@@ -2513,6 +2515,7 @@ struct rt6_info *rt6_add_dflt_router(const struct
in6_addr *gwaddr,
                .fc_ifindex     = dev->ifindex,
                .fc_flags       = RTF_GATEWAY | RTF_ADDRCONF | RTF_DEFAULT |
                                  RTF_UP | RTF_EXPIRES | RTF_PREF(pref),
+               .fc_protocol    = RTPROT_RA,
                .fc_nlinfo.portid = 0,
                .fc_nlinfo.nlh = NULL,
                .fc_nlinfo.nl_net = dev_net(dev),
@@ -3424,14 +3427,6 @@ static int rt6_fill_node(struct net *net,
        rtm->rtm_flags = 0;
        rtm->rtm_scope = RT_SCOPE_UNIVERSE;
        rtm->rtm_protocol = rt->rt6i_protocol;
-       if (rt->rt6i_flags & RTF_DYNAMIC)
-               rtm->rtm_protocol = RTPROT_REDIRECT;
-       else if (rt->rt6i_flags & RTF_ADDRCONF) {
-               if (rt->rt6i_flags & (RTF_DEFAULT | RTF_ROUTEINFO))
-                       rtm->rtm_protocol = RTPROT_RA;
-               else
-                       rtm->rtm_protocol = RTPROT_KERNEL;
-       }

        if (rt->rt6i_flags & RTF_CACHE)
                rtm->rtm_flags |= RTM_F_CLONED;