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net: don't return invalid table id error when we fall back to PF_UNSPEC
In case we can't find a ->dumpit callback for the requested (family,type) pair, we fall back to (PF_UNSPEC,type). In effect, we're in the same situation as if userspace had requested a PF_UNSPEC dump. For RTM_GETROUTE, that handler is rtnl_dump_all, which calls all the registered RTM_GETROUTE handlers. The requested table id may or may not exist for all of those families. commit ae677bbb ("net: Don't return invalid table id error when dumping all families") fixed the problem when userspace explicitly requests a PF_UNSPEC dump, but missed the fallback case. For example, when we pass ipv6.disable=1 to a kernel with CONFIG_IP_MROUTE=y and CONFIG_IP_MROUTE_MULTIPLE_TABLES=y, the (PF_INET6, RTM_GETROUTE) handler isn't registered, so we end up in rtnl_dump_all, and listing IPv6 routes will unexpectedly print: # ip -6 r Error: ipv4: MR table does not exist. Dump terminated commit ae677bbb introduced the dump_all_families variable, which gets set when userspace requests a PF_UNSPEC dump. However, we can't simply set the family to PF_UNSPEC in rtnetlink_rcv_msg in the fallback case to get dump_all_families == true, because some messages types (for example RTM_GETRULE and RTM_GETNEIGH) only register the PF_UNSPEC handler and use the family to filter in the kernel what is dumped to userspace. We would then export more entries, that userspace would have to filter. iproute does that, but other programs may not. Instead, this patch removes dump_all_families and updates the RTM_GETROUTE handlers to check if the family that is being dumped is their own. When it's not, which covers both the intentional PF_UNSPEC dumps (as dump_all_families did) and the fallback case, ignore the missing table id error. Fixes: cb167893 ("net: Plumb support for filtering ipv4 and ipv6 multicast route dumps") Signed-off-by:Sabrina Dubroca <sd@queasysnail.net> Reviewed-by: