[PKT_SCHED] dsmark: handle cloned and non-linear skb's

Make dsmark work properly with non-linear and cloned skb's
Before modifying the header, it needs to check that skb header is
writeable.

Note: this makes the assumption, that if it queues a good skb
then a good skb will come out of the embedded qdisc.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 4 deletions

diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index d96eaf0aa6b8..ad30b7b4769f 100644
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -187,13 +187,19 @@ static int dsmark_enqueue(struct sk_buff *skb,struct Qdisc *sch)
         pr_debug("dsmark_enqueue(skb %p,sch %p,[qdisc %p])\n", skb, sch, p);
 
         if (p->set_tc_index) {
-                /* FIXME: Safe with non-linear skbs? --RR */
                 switch (skb->protocol) {
                         case __constant_htons(ETH_P_IP):
+                                if (skb_cow_head(skb, sizeof(struct iphdr)))
+                                        goto drop;
+
                                 skb->tc_index = ipv4_get_dsfield(ip_hdr(skb))
                                         & ~INET_ECN_MASK;
                                 break;
+
                         case __constant_htons(ETH_P_IPV6):
+                                if (skb_cow_head(skb, sizeof(struct ipv6hdr)))
+                                        goto drop;
+
                                 skb->tc_index = ipv6_get_dsfield(ipv6_hdr(skb))
                                         & ~INET_ECN_MASK;
                                 break;
@@ -217,14 +223,14 @@ static int dsmark_enqueue(struct sk_buff *skb,struct Qdisc *sch)
                 case TC_ACT_STOLEN:
                         kfree_skb(skb);
                         return NET_XMIT_SUCCESS;
+
                 case TC_ACT_SHOT:
-                        kfree_skb(skb);
-                        sch->qstats.drops++;
-                        return NET_XMIT_BYPASS;
+                        goto drop;
 #endif
                 case TC_ACT_OK:
                         skb->tc_index = TC_H_MIN(res.classid);
                         break;
+
                 default:
                         if (p->default_index != NO_DEFAULT_INDEX)
                                 skb->tc_index = p->default_index;
@@ -243,6 +249,11 @@ static int dsmark_enqueue(struct sk_buff *skb,struct Qdisc *sch)
         sch->q.qlen++;
 
         return NET_XMIT_SUCCESS;
+
+drop:
+        kfree_skb(skb);
+        sch->qstats.drops++;
+        return NET_XMIT_BYPASS;
 }
 
 static struct sk_buff *dsmark_dequeue(struct Qdisc *sch)