net: mpls: bump maximum number of labels

Allow users to push down more labels per MPLS route. With the previous
patches, no memory allocations are based on MAX_NEW_LABELS; the limit
is only used to keep userspace in check.

At this point MAX_NEW_LABELS is only used for mpls_route_config (copying
route data from userspace) and processing nexthops looking for the max
number of labels across the route spec.

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

2 files changed, 71 insertions, 34 deletions

diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index f84c52b6eafc..10daefd7f938 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -24,7 +24,10 @@
 #include <net/nexthop.h>
 #include "internal.h"
 
-#define MAX_NEW_LABELS 2
+/* put a reasonable limit on the number of labels
+ * we will accept from userspace
+ */
+#define MAX_NEW_LABELS  30
 
 /* max memory we will use for mpls_route */
 #define MAX_MPLS_ROUTE_MEM      4096
@@ -698,9 +701,6 @@ static int mpls_nh_build_from_cfg(struct mpls_route_config *cfg,
                 return -ENOMEM;
 
         err = -EINVAL;
-        /* Ensure only a supported number of labels are present */
-        if (cfg->rc_output_labels > MAX_NEW_LABELS)
-                goto errout;
 
         nh->nh_labels = cfg->rc_output_labels;
         for (i = 0; i < nh->nh_labels; i++)
@@ -725,7 +725,7 @@ errout:
 
 static int mpls_nh_build(struct net *net, struct mpls_route *rt,
                          struct mpls_nh *nh, int oif, struct nlattr *via,
-                         struct nlattr *newdst)
+                         struct nlattr *newdst, u8 max_labels)
 {
         int err = -ENOMEM;
 
@@ -733,7 +733,7 @@ static int mpls_nh_build(struct net *net, struct mpls_route *rt,
                 goto errout;
 
         if (newdst) {
-                err = nla_get_labels(newdst, MAX_NEW_LABELS,
+                err = nla_get_labels(newdst, max_labels,
                                      &nh->nh_labels, nh->nh_label);
                 if (err)
                         goto errout;
@@ -759,21 +759,19 @@ errout:
 }
 
 static u8 mpls_count_nexthops(struct rtnexthop *rtnh, int len,
-                              u8 cfg_via_alen, u8 *max_via_alen)
+                              u8 cfg_via_alen, u8 *max_via_alen,
+                              u8 *max_labels)
 {
         int remaining = len;
         u8 nhs = 0;
 
-        if (!rtnh) {
-                *max_via_alen = cfg_via_alen;
-                return 1;
-        }
-
         *max_via_alen = 0;
+        *max_labels = 0;
 
         while (rtnh_ok(rtnh, remaining)) {
                 struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
                 int attrlen;
+                u8 n_labels = 0;
 
                 attrlen = rtnh_attrlen(rtnh);
                 nla = nla_find(attrs, attrlen, RTA_VIA);
@@ -787,6 +785,13 @@ static u8 mpls_count_nexthops(struct rtnexthop *rtnh, int len,
                                                       via_alen);
                 }
 
+                nla = nla_find(attrs, attrlen, RTA_NEWDST);
+                if (nla &&
+                    nla_get_labels(nla, MAX_NEW_LABELS, &n_labels, NULL) != 0)
+                        return 0;
+
+                *max_labels = max_t(u8, *max_labels, n_labels);
+
                 /* number of nexthops is tracked by a u8.
                  * Check for overflow.
                  */
@@ -802,7 +807,7 @@ static u8 mpls_count_nexthops(struct rtnexthop *rtnh, int len,
 }
 
 static int mpls_nh_build_multi(struct mpls_route_config *cfg,
-                               struct mpls_route *rt)
+                               struct mpls_route *rt, u8 max_labels)
 {
         struct rtnexthop *rtnh = cfg->rc_mp;
         struct nlattr *nla_via, *nla_newdst;
@@ -835,7 +840,8 @@ static int mpls_nh_build_multi(struct mpls_route_config *cfg,
                 }
 
                 err = mpls_nh_build(cfg->rc_nlinfo.nl_net, rt, nh,
-                                    rtnh->rtnh_ifindex, nla_via, nla_newdst);
+                                    rtnh->rtnh_ifindex, nla_via, nla_newdst,
+                                    max_labels);
                 if (err)
                         goto errout;
 
@@ -862,6 +868,7 @@ static int mpls_route_add(struct mpls_route_config *cfg)
         int err = -EINVAL;
         u8 max_via_alen;
         unsigned index;
+        u8 max_labels;
         u8 nhs;
 
         index = cfg->rc_label;
@@ -900,13 +907,21 @@ static int mpls_route_add(struct mpls_route_config *cfg)
                 goto errout;
 
         err = -EINVAL;
-        nhs = mpls_count_nexthops(cfg->rc_mp, cfg->rc_mp_len,
-                                  cfg->rc_via_alen, &max_via_alen);
+        if (cfg->rc_mp) {
+                nhs = mpls_count_nexthops(cfg->rc_mp, cfg->rc_mp_len,
+                                          cfg->rc_via_alen, &max_via_alen,
+                                          &max_labels);
+        } else {
+                max_via_alen = cfg->rc_via_alen;
+                max_labels = cfg->rc_output_labels;
+                nhs = 1;
+        }
+
         if (nhs == 0)
                 goto errout;
 
         err = -ENOMEM;
-        rt = mpls_rt_alloc(nhs, max_via_alen, MAX_NEW_LABELS);
+        rt = mpls_rt_alloc(nhs, max_via_alen, max_labels);
         if (IS_ERR(rt)) {
                 err = PTR_ERR(rt);
                 goto errout;
@@ -917,7 +932,7 @@ static int mpls_route_add(struct mpls_route_config *cfg)
         rt->rt_ttl_propagate = cfg->rc_ttl_propagate;
 
         if (cfg->rc_mp)
-                err = mpls_nh_build_multi(cfg, rt);
+                err = mpls_nh_build_multi(cfg, rt, max_labels);
         else
                 err = mpls_nh_build_from_cfg(cfg, rt);
         if (err)
@@ -1531,16 +1546,18 @@ int nla_put_labels(struct sk_buff *skb, int attrtype,
 EXPORT_SYMBOL_GPL(nla_put_labels);
 
 int nla_get_labels(const struct nlattr *nla,
-                   u32 max_labels, u8 *labels, u32 label[])
+                   u8 max_labels, u8 *labels, u32 label[])
 {
         unsigned len = nla_len(nla);
-        unsigned nla_labels;
         struct mpls_shim_hdr *nla_label;
+        u8 nla_labels;
         bool bos;
         int i;
 
-        /* len needs to be an even multiple of 4 (the label size) */
-        if (len & 3)
+        /* 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)
                 return -EINVAL;
 
         /* Limit the number of new labels allowed */
@@ -1548,6 +1565,10 @@ int nla_get_labels(const struct nlattr *nla,
         if (nla_labels > max_labels)
                 return -EINVAL;
 
+        /* when label == NULL, caller wants number of labels */
+        if (!label)
+                goto out;
+
         nla_label = nla_data(nla);
         bos = true;
         for (i = nla_labels - 1; i >= 0; i--, bos = false) {
@@ -1571,6 +1592,7 @@ int nla_get_labels(const struct nlattr *nla,
 
                 label[i] = dec.label;
         }
+out:
         *labels = nla_labels;
         return 0;
 }
@@ -1632,7 +1654,6 @@ static int rtm_to_route_config(struct sk_buff *skb,  struct nlmsghdr *nlh,
 
         err = -EINVAL;
         rtm = nlmsg_data(nlh);
-        memset(cfg, 0, sizeof(*cfg));
 
         if (rtm->rtm_family != AF_MPLS)
                 goto errout;
@@ -1731,27 +1752,43 @@ errout:
 
 static int mpls_rtm_delroute(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
-        struct mpls_route_config cfg;
+        struct mpls_route_config *cfg;
         int err;
 
-        err = rtm_to_route_config(skb, nlh, &cfg);
+        cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
+        if (!cfg)
+                return -ENOMEM;
+
+        err = rtm_to_route_config(skb, nlh, cfg);
         if (err < 0)
-                return err;
+                goto out;
 
-        return mpls_route_del(&cfg);
+        err = mpls_route_del(cfg);
+out:
+        kfree(cfg);
+
+        return err;
 }
 
 
 static int mpls_rtm_newroute(struct sk_buff *skb, struct nlmsghdr *nlh)
 {
-        struct mpls_route_config cfg;
+        struct mpls_route_config *cfg;
         int err;
 
-        err = rtm_to_route_config(skb, nlh, &cfg);
+        cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
+        if (!cfg)
+                return -ENOMEM;
+
+        err = rtm_to_route_config(skb, nlh, cfg);
         if (err < 0)
-                return err;
+                goto out;
 
-        return mpls_route_add(&cfg);
+        err = mpls_route_add(cfg);
+out:
+        kfree(cfg);
+
+        return err;
 }
 
 static int mpls_dump_route(struct sk_buff *skb, u32 portid, u32 seq, int event,
@@ -1980,7 +2017,7 @@ static int resize_platform_label_table(struct net *net, size_t limit)
         /* In case the predefined labels need to be populated */
         if (limit > MPLS_LABEL_IPV4NULL) {
                 struct net_device *lo = net->loopback_dev;
-                rt0 = mpls_rt_alloc(1, lo->addr_len, MAX_NEW_LABELS);
+                rt0 = mpls_rt_alloc(1, lo->addr_len, 0);
                 if (IS_ERR(rt0))
                         goto nort0;
                 RCU_INIT_POINTER(rt0->rt_nh->nh_dev, lo);
@@ -1994,7 +2031,7 @@ static int resize_platform_label_table(struct net *net, size_t limit)
         }
         if (limit > MPLS_LABEL_IPV6NULL) {
                 struct net_device *lo = net->loopback_dev;
-                rt2 = mpls_rt_alloc(1, lo->addr_len, MAX_NEW_LABELS);
+                rt2 = mpls_rt_alloc(1, lo->addr_len, 0);
                 if (IS_ERR(rt2))
                         goto nort2;
                 RCU_INIT_POINTER(rt2->rt_nh->nh_dev, lo);
diff --git a/net/mpls/internal.h b/net/mpls/internal.h
index cc324c022049..c5d2f5bc37ec 100644
--- a/net/mpls/internal.h
+++ b/net/mpls/internal.h
@@ -197,7 +197,7 @@ static inline struct mpls_dev *mpls_dev_get(const struct net_device *dev)
 
 int nla_put_labels(struct sk_buff *skb, int attrtype,  u8 labels,
                    const u32 label[]);
-int nla_get_labels(const struct nlattr *nla, u32 max_labels, u8 *labels,
+int nla_get_labels(const struct nlattr *nla, u8 max_labels, u8 *labels,
                    u32 label[]);
 int nla_get_via(const struct nlattr *nla, u8 *via_alen, u8 *via_table,
                 u8 via[]);