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>

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 @@ static int mpls_nh_build_from_cfg(struct mpls_route_config *cfg,
 
 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 @@ static int mpls_nh_build(struct net *net, struct mpls_route *rt,
 }
 
 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;
+	if (cfg->rc_mp) {
 		nhs = mpls_count_nexthops(cfg->rc_mp, cfg->rc_mp_len,
-				  cfg->rc_via_alen, &max_via_alen);
+					  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 @@ static int rtm_to_route_config(struct sk_buff *skb,  struct nlmsghdr *nlh,
 
 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);

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[]);