[NET_SCHED]: act_api: qdisc internal reclassify support

The behaviour of NET_CLS_POLICE for TC_POLICE_RECLASSIFY was to return
it to the qdisc, which could handle it internally or ignore it. With
NET_CLS_ACT however, tc_classify starts over at the first classifier
and never returns it to the qdisc. This makes it impossible to support
qdisc-internal reclassification, which in turn makes it impossible to
remove the old NET_CLS_POLICE code without breaking compatibility since
we have two qdiscs (CBQ and ATM) that support this.

This patch adds a tc_classify_compat function that handles
reclassification the old way and changes CBQ and ATM to use it.

This again is of course not fully backwards compatible with the previous
NET_CLS_ACT behaviour. Unfortunately there is no way to fully maintain
compatibility *and* support qdisc internal reclassification with
NET_CLS_ACT, but this seems like the better choice over keeping the two
incompatible options around forever.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 29 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 4fd0beca9450..13c09bc32aa3 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1145,47 +1145,57 @@ static int tc_dump_tclass(struct sk_buff *skb, struct netlink_callback *cb)
    to this qdisc, (optionally) tests for protocol and asks
    specific classifiers.
  */
+int tc_classify_compat(struct sk_buff *skb, struct tcf_proto *tp,
+                       struct tcf_result *res)
+{
+        __be16 protocol = skb->protocol;
+        int err = 0;
+
+        for (; tp; tp = tp->next) {
+                if ((tp->protocol == protocol ||
+                     tp->protocol == htons(ETH_P_ALL)) &&
+                    (err = tp->classify(skb, tp, res)) >= 0) {
+#ifdef CONFIG_NET_CLS_ACT
+                        if (err != TC_ACT_RECLASSIFY && skb->tc_verd)
+                                skb->tc_verd = SET_TC_VERD(skb->tc_verd, 0);
+#endif
+                        return err;
+                }
+        }
+        return -1;
+}
+EXPORT_SYMBOL(tc_classify_compat);
+
 int tc_classify(struct sk_buff *skb, struct tcf_proto *tp,
-        struct tcf_result *res)
+                struct tcf_result *res)
 {
         int err = 0;
-        __be16 protocol = skb->protocol;
+        __be16 protocol;
 #ifdef CONFIG_NET_CLS_ACT
         struct tcf_proto *otp = tp;
 reclassify:
 #endif
         protocol = skb->protocol;
 
-        for ( ; tp; tp = tp->next) {
-                if ((tp->protocol == protocol ||
-                        tp->protocol == htons(ETH_P_ALL)) &&
-                        (err = tp->classify(skb, tp, res)) >= 0) {
+        err = tc_classify_compat(skb, tp, res);
 #ifdef CONFIG_NET_CLS_ACT
-                        if ( TC_ACT_RECLASSIFY == err) {
-                                __u32 verd = (__u32) G_TC_VERD(skb->tc_verd);
-                                tp = otp;
-
-                                if (MAX_REC_LOOP < verd++) {
-                                        printk("rule prio %d protocol %02x reclassify is buggy packet dropped\n",
-                                                tp->prio&0xffff, ntohs(tp->protocol));
-                                        return TC_ACT_SHOT;
-                                }
-                                skb->tc_verd = SET_TC_VERD(skb->tc_verd,verd);
-                                goto reclassify;
-                        } else {
-                                if (skb->tc_verd)
-                                        skb->tc_verd = SET_TC_VERD(skb->tc_verd,0);
-                                return err;
-                        }
-#else
-
-                        return err;
-#endif
+        if (err == TC_ACT_RECLASSIFY) {
+                u32 verd = G_TC_VERD(skb->tc_verd);
+                tp = otp;
+
+                if (verd++ >= MAX_REC_LOOP) {
+                        printk("rule prio %u protocol %02x reclassify loop, "
+                               "packet dropped\n",
+                               tp->prio&0xffff, ntohs(tp->protocol));
+                        return TC_ACT_SHOT;
                 }
-
+                skb->tc_verd = SET_TC_VERD(skb->tc_verd, verd);
+                goto reclassify;
         }
-        return -1;
+#endif
+        return err;
 }
+EXPORT_SYMBOL(tc_classify);
 
 void tcf_destroy(struct tcf_proto *tp)
 {
@@ -1252,4 +1262,3 @@ EXPORT_SYMBOL(qdisc_get_rtab);
 EXPORT_SYMBOL(qdisc_put_rtab);
 EXPORT_SYMBOL(register_qdisc);
 EXPORT_SYMBOL(unregister_qdisc);
-EXPORT_SYMBOL(tc_classify);