net: Fill in extack for mpls lwt encap

Fill in extack for errors in build_state for mpls lwt encap including
passing extack to nla_get_labels and adding error messages for failures
in it.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 39 insertions, 10 deletions

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 257ec66009da..f3830951fb1c 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -728,8 +728,8 @@ static int mpls_nh_build(struct net *net, struct mpls_route *rt,
                 goto errout;
 
         if (newdst) {
-                err = nla_get_labels(newdst, max_labels,
-                                     &nh->nh_labels, nh->nh_label);
+                err = nla_get_labels(newdst, max_labels, &nh->nh_labels,
+                                     nh->nh_label, NULL);
                 if (err)
                         goto errout;
         }
@@ -782,7 +782,8 @@ static u8 mpls_count_nexthops(struct rtnexthop *rtnh, int len,
 
                 nla = nla_find(attrs, attrlen, RTA_NEWDST);
                 if (nla &&
-                    nla_get_labels(nla, MAX_NEW_LABELS, &n_labels, NULL) != 0)
+                    nla_get_labels(nla, MAX_NEW_LABELS, &n_labels,
+                                   NULL, NULL) != 0)
                         return 0;
 
                 *max_labels = max_t(u8, *max_labels, n_labels);
@@ -1541,8 +1542,8 @@ int nla_put_labels(struct sk_buff *skb, int attrtype,
 }
 EXPORT_SYMBOL_GPL(nla_put_labels);
 
-int nla_get_labels(const struct nlattr *nla,
-                   u8 max_labels, u8 *labels, u32 label[])
+int nla_get_labels(const struct nlattr *nla, u8 max_labels, u8 *labels,
+                   u32 label[], struct netlink_ext_ack *extack)
 {
         unsigned len = nla_len(nla);
         struct mpls_shim_hdr *nla_label;
@@ -1553,13 +1554,18 @@ int nla_get_labels(const struct nlattr *nla,
         /* len needs to be an even multiple of 4 (the label size). Number
          * of labels is a u8 so check for overflow.
          */
-        if (len & 3 || len / 4 > 255)
+        if (len & 3 || len / 4 > 255) {
+                NL_SET_ERR_MSG_ATTR(extack, nla,
+                                    "Invalid length for labels attribute");
                 return -EINVAL;
+        }
 
         /* Limit the number of new labels allowed */
         nla_labels = len/4;
-        if (nla_labels > max_labels)
+        if (nla_labels > max_labels) {
+                NL_SET_ERR_MSG(extack, "Too many labels");
                 return -EINVAL;
+        }
 
         /* when label == NULL, caller wants number of labels */
         if (!label)
@@ -1574,8 +1580,29 @@ int nla_get_labels(const struct nlattr *nla,
                 /* Ensure the bottom of stack flag is properly set
                  * and ttl and tc are both clear.
                  */
-                if ((dec.bos != bos) || dec.ttl || dec.tc)
+                if (dec.ttl) {
+                        NL_SET_ERR_MSG_ATTR(extack, nla,
+                                            "TTL in label must be 0");
+                        return -EINVAL;
+                }
+
+                if (dec.tc) {
+                        NL_SET_ERR_MSG_ATTR(extack, nla,
+                                            "Traffic class in label must be 0");
                         return -EINVAL;
+                }
+
+                if (dec.bos != bos) {
+                        NL_SET_BAD_ATTR(extack, nla);
+                        if (bos) {
+                                NL_SET_ERR_MSG(extack,
+                                               "BOS bit must be set in first label");
+                        } else {
+                                NL_SET_ERR_MSG(extack,
+                                               "BOS bit can only be set in first label");
+                        }
+                        return -EINVAL;
+                }
 
                 switch (dec.label) {
                 case MPLS_LABEL_IMPLNULL:
@@ -1583,6 +1610,8 @@ int nla_get_labels(const struct nlattr *nla,
                          * assign and distribute, but which never
                          * actually appears in the encapsulation.
                          */
+                        NL_SET_ERR_MSG_ATTR(extack, nla,
+                                            "Implicit NULL Label (3) can not be used in encapsulation");
                         return -EINVAL;
                 }
 
@@ -1696,14 +1725,14 @@ static int rtm_to_route_config(struct sk_buff *skb,  struct nlmsghdr *nlh,
                 case RTA_NEWDST:
                         if (nla_get_labels(nla, MAX_NEW_LABELS,
                                            &cfg->rc_output_labels,
-                                           cfg->rc_output_label))
+                                           cfg->rc_output_label, NULL))
                                 goto errout;
                         break;
                 case RTA_DST:
                 {
                         u8 label_count;
                         if (nla_get_labels(nla, 1, &label_count,
-                                           &cfg->rc_label))
+                                           &cfg->rc_label, NULL))
                                 goto errout;
 
                         /* Reserved labels may not be set */