net: ip6mr: add RTM_GETROUTE netlink op

The IPv6 multicast routing code previously implemented only the dump
variant of RTM_GETROUTE.  Implement single MFC item retrieval by copying
and adapting the respective IPv4 code.

Tested against FRRouting's IPv6 PIM stack.

Signed-off-by: David Lamparter <equinox@diac24.net>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index ec6e150..d546fc0 100644 (file)
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -95,6 +95,8 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt,
 static void mr6_netlink_event(struct mr_table *mrt, struct mfc6_cache *mfc,
                              int cmd);
 static void mrt6msg_netlink_event(const struct mr_table *mrt, struct sk_buff *pkt);
+static int ip6mr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
+                             struct netlink_ext_ack *extack);
 static int ip6mr_rtm_dumproute(struct sk_buff *skb,
                               struct netlink_callback *cb);
 static void mroute_clean_tables(struct mr_table *mrt, int flags);
@@ -1390,7 +1392,7 @@ int __init ip6_mr_init(void)
        }
 #endif
        err = rtnl_register_module(THIS_MODULE, RTNL_FAMILY_IP6MR, RTM_GETROUTE,
-                                  NULL, ip6mr_rtm_dumproute, 0);
+                                  ip6mr_rtm_getroute, ip6mr_rtm_dumproute, 0);
        if (err == 0)
                return 0;
 
@@ -2510,6 +2512,95 @@ errout:
        rtnl_set_sk_err(net, RTNLGRP_IPV6_MROUTE_R, -ENOBUFS);
 }
 
+static const struct nla_policy ip6mr_getroute_policy[RTA_MAX + 1] = {
+       [RTA_SRC]               = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
+       [RTA_DST]               = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
+       [RTA_TABLE]             = { .type = NLA_U32 },
+};
+
+static int ip6mr_rtm_valid_getroute_req(struct sk_buff *skb,
+                                       const struct nlmsghdr *nlh,
+                                       struct nlattr **tb,
+                                       struct netlink_ext_ack *extack)
+{
+       struct rtmsg *rtm;
+       int err;
+
+       err = nlmsg_parse(nlh, sizeof(*rtm), tb, RTA_MAX, ip6mr_getroute_policy,
+                         extack);
+       if (err)
+               return err;
+
+       rtm = nlmsg_data(nlh);
+       if ((rtm->rtm_src_len && rtm->rtm_src_len != 128) ||
+           (rtm->rtm_dst_len && rtm->rtm_dst_len != 128) ||
+           rtm->rtm_tos || rtm->rtm_table || rtm->rtm_protocol ||
+           rtm->rtm_scope || rtm->rtm_type || rtm->rtm_flags) {
+               NL_SET_ERR_MSG_MOD(extack,
+                                  "Invalid values in header for multicast route get request");
+               return -EINVAL;
+       }
+
+       if ((tb[RTA_SRC] && !rtm->rtm_src_len) ||
+           (tb[RTA_DST] && !rtm->rtm_dst_len)) {
+               NL_SET_ERR_MSG_MOD(extack, "rtm_src_len and rtm_dst_len must be 128 for IPv6");
+               return -EINVAL;
+       }
+
+       return 0;
+}
+
+static int ip6mr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
+                             struct netlink_ext_ack *extack)
+{
+       struct net *net = sock_net(in_skb->sk);
+       struct in6_addr src = {}, grp = {};
+       struct nlattr *tb[RTA_MAX + 1];
+       struct mfc6_cache *cache;
+       struct mr_table *mrt;
+       struct sk_buff *skb;
+       u32 tableid;
+       int err;
+
+       err = ip6mr_rtm_valid_getroute_req(in_skb, nlh, tb, extack);
+       if (err < 0)
+               return err;
+
+       if (tb[RTA_SRC])
+               src = nla_get_in6_addr(tb[RTA_SRC]);
+       if (tb[RTA_DST])
+               grp = nla_get_in6_addr(tb[RTA_DST]);
+       tableid = tb[RTA_TABLE] ? nla_get_u32(tb[RTA_TABLE]) : 0;
+
+       mrt = ip6mr_get_table(net, tableid ?: RT_TABLE_DEFAULT);
+       if (!mrt) {
+               NL_SET_ERR_MSG_MOD(extack, "MR table does not exist");
+               return -ENOENT;
+       }
+
+       /* entries are added/deleted only under RTNL */
+       rcu_read_lock();
+       cache = ip6mr_cache_find(mrt, &src, &grp);
+       rcu_read_unlock();
+       if (!cache) {
+               NL_SET_ERR_MSG_MOD(extack, "MR cache entry not found");
+               return -ENOENT;
+       }
+
+       skb = nlmsg_new(mr6_msgsize(false, mrt->maxvif), GFP_KERNEL);
+       if (!skb)
+               return -ENOBUFS;
+
+       err = ip6mr_fill_mroute(mrt, skb, NETLINK_CB(in_skb).portid,
+                               nlh->nlmsg_seq, cache, RTM_NEWROUTE, 0);
+       if (err < 0) {
+               kfree_skb(skb);
+               return err;
+       }
+
+       return rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
+}
+
 static int ip6mr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
 {
        const struct nlmsghdr *nlh = cb->nlh;