[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>

diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index d96eaf0aa6b8b6bb8809c682b5338732e84017ff..ad30b7b4769f8c47d328f6492db0d35dbd7a6159 100644 (file)
--- 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)