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net: sched: use counter to break reclassify loops 

Seems all we want here is to avoid endless 'goto reclassify' loop.
tc_classify_compat even resets this counter when something other
than TC_ACT_RECLASSIFY is returned, so this skb-counter doesn't
break hypothetical loops induced by something other than perpetual
TC_ACT_RECLASSIFY return values.

skb_act_clone is now identical to skb_clone, so just use that.

Tested with following (bogus) filter:
tc filter add dev eth0 parent ffff: \
 protocol ip u32 match u32 0 0 police rate 10Kbit burst \
 64000 mtu 1500 action reclassify

Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal 2015-05-11 19:50:41 +02:00 committed by David S. Miller
parent b04096ff33
commit e578d9c025
5 changed files with 5 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/networking/tc-actions-env-rules.txt
View File

@ -8,10 +8,6 @@ For example if your action queues a packet to be processed later,
or intentionally branches by redirecting a packet, then you need to
clone the packet.
There are certain fields in the skb tc_verd that need to be reset so we
avoid loops, etc. A few are generic enough that skb_act_clone()
resets them for you, so invoke skb_act_clone() rather than skb_clone().
2) If you munge any packet thou shalt call pskb_expand_head in the case
someone else is referencing the skb. After that you "own" the skb.

15
include/net/sch_generic.h
View File

@ -739,21 +739,6 @@ static inline u32 qdisc_l2t(struct qdisc_rate_table* rtab, unsigned int pktlen)
return rtab->data[slot];
}
#ifdef CONFIG_NET_CLS_ACT
static inline struct sk_buff *skb_act_clone(struct sk_buff *skb, gfp_t gfp_mask,
int action)
{
struct sk_buff *n;
n = skb_clone(skb, gfp_mask);
if (n) {
n->tc_verd = SET_TC_VERD(n->tc_verd, 0);
}
return n;
}
#endif
struct psched_ratecfg {
u64 rate_bytes_ps; /* bytes per second */
u32 mult;

2
include/uapi/linux/pkt_cls.h
View File

@ -44,13 +44,13 @@ bits 9,10,11: redirect counter - redirect TTL. Loop avoidance
#define TC_OK2MUNGE _TC_MAKEMASK1(1)
#define SET_TC_OK2MUNGE(v) ( TC_OK2MUNGE | (v & ~TC_OK2MUNGE))
#define CLR_TC_OK2MUNGE(v) ( v & ~TC_OK2MUNGE)
#endif
#define S_TC_VERD _TC_MAKE32(2)
#define M_TC_VERD _TC_MAKEMASK(4,S_TC_VERD)
#define G_TC_VERD(x) _TC_GETVALUE(x,S_TC_VERD,M_TC_VERD)
#define V_TC_VERD(x) _TC_MAKEVALUE(x,S_TC_VERD)
#define SET_TC_VERD(v,n) ((V_TC_VERD(n)) | (v & ~M_TC_VERD))
#endif
#define S_TC_FROM _TC_MAKE32(6)
#define M_TC_FROM _TC_MAKEMASK(2,S_TC_FROM)

2
net/sched/act_mirred.c
View File

@ -151,7 +151,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
}
at = G_TC_AT(skb->tc_verd);
skb2 = skb_act_clone(skb, GFP_ATOMIC, m->tcf_action);
skb2 = skb_clone(skb, GFP_ATOMIC);
if (skb2 == NULL)
goto out;

12
net/sched/sch_api.c
View File

@ -1816,13 +1816,8 @@ int tc_classify_compat(struct sk_buff *skb, const struct tcf_proto *tp,
continue;
err = tp->classify(skb, tp, res);
if (err >= 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
if (err >= 0)
return err;
}
}
return -1;
}
@ -1834,23 +1829,22 @@ int tc_classify(struct sk_buff *skb, const struct tcf_proto *tp,
int err = 0;
#ifdef CONFIG_NET_CLS_ACT
const struct tcf_proto *otp = tp;
int limit = 0;
reclassify:
#endif
err = tc_classify_compat(skb, tp, res);
#ifdef CONFIG_NET_CLS_ACT
if (err == TC_ACT_RECLASSIFY) {
u32 verd = G_TC_VERD(skb->tc_verd);
tp = otp;
if (verd++ >= MAX_REC_LOOP) {
if (unlikely(limit++ >= MAX_REC_LOOP)) {
net_notice_ratelimited("%s: packet reclassify loop rule prio %u protocol %02x\n",
tp->q->ops->id,
tp->prio & 0xffff,
ntohs(tp->protocol));
return TC_ACT_SHOT;
}
skb->tc_verd = SET_TC_VERD(skb->tc_verd, verd);
goto reclassify;
}
#endif