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net: add a noref bit on skb dst

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Use low order bit of skb->_skb_dst to tell dst is not refcounted.

Change _skb_dst to _skb_refdst to make sure all uses are catched.

skb_dst() returns the dst, regardless of noref bit set or not, but
with a lockdep check to make sure a noref dst is not given if current
user is not rcu protected.

New skb_dst_set_noref() helper to set an notrefcounted dst on a skb.
(with lockdep check)

skb_dst_drop() drops a reference only if skb dst was refcounted.

skb_dst_force() helper is used to force a refcount on dst, when skb
is queued and not anymore RCU protected.

Use skb_dst_force() in __sk_add_backlog(), __dev_xmit_skb() if
!IFF_XMIT_DST_RELEASE or skb enqueued on qdisc queue, in
sock_queue_rcv_skb(), in __nf_queue().

Use skb_dst_force() in dev_requeue_skb().

Note: dst_use_noref() still dirties dst, we might transform it
later to do one dirtying per jiffies.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2010-05-11 23:19:48 +00:00 committed by David S. Miller
parent ebda37c27d
commit 7fee226ad2
12 changed files with 134 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
include/linux/skbuff.h
View File

@ -264,7 +264,7 @@ typedef unsigned char *sk_buff_data_t;
* @transport_header: Transport layer header
* @network_header: Network layer header
* @mac_header: Link layer header
* @_skb_dst: destination entry
* @_skb_refdst: destination entry (with norefcount bit)
* @sp: the security path, used for xfrm
* @cb: Control buffer. Free for use by every layer. Put private vars here
* @len: Length of actual data
@ -328,7 +328,7 @@ struct sk_buff {
*/
char cb[48] __aligned(8);
unsigned long _skb_dst;
unsigned long _skb_refdst;
#ifdef CONFIG_XFRM
struct sec_path *sp;
#endif
@ -419,14 +419,64 @@ struct sk_buff {
#include <asm/system.h>
/*
* skb might have a dst pointer attached, refcounted or not.
* _skb_refdst low order bit is set if refcount was _not_ taken
*/
#define SKB_DST_NOREF 1UL
#define SKB_DST_PTRMASK ~(SKB_DST_NOREF)
/**
* skb_dst - returns skb dst_entry
* @skb: buffer
*
* Returns skb dst_entry, regardless of reference taken or not.
*/
static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
{
return (struct dst_entry *)skb->_skb_dst;
/* If refdst was not refcounted, check we still are in a
* rcu_read_lock section
*/
WARN_ON((skb->_skb_refdst & SKB_DST_NOREF) &&
!rcu_read_lock_held() &&
!rcu_read_lock_bh_held());
return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK);
}
/**
* skb_dst_set - sets skb dst
* @skb: buffer
* @dst: dst entry
*
* Sets skb dst, assuming a reference was taken on dst and should
* be released by skb_dst_drop()
*/
static inline void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)
{
skb->_skb_dst = (unsigned long)dst;
skb->_skb_refdst = (unsigned long)dst;
}
/**
* skb_dst_set_noref - sets skb dst, without a reference
* @skb: buffer
* @dst: dst entry
*
* Sets skb dst, assuming a reference was not taken on dst
* skb_dst_drop() should not dst_release() this dst
*/
static inline void skb_dst_set_noref(struct sk_buff *skb, struct dst_entry *dst)
{
WARN_ON(!rcu_read_lock_held() && !rcu_read_lock_bh_held());
skb->_skb_refdst = (unsigned long)dst | SKB_DST_NOREF;
}
/**
* skb_dst_is_noref - Test if skb dst isnt refcounted
* @skb: buffer
*/
static inline bool skb_dst_is_noref(const struct sk_buff *skb)
{
return (skb->_skb_refdst & SKB_DST_NOREF) && skb_dst(skb);
}
static inline struct rtable *skb_rtable(const struct sk_buff *skb)

48
include/net/dst.h
View File

@ -168,6 +168,12 @@ static inline void dst_use(struct dst_entry *dst, unsigned long time)
dst->lastuse = time;
}
static inline void dst_use_noref(struct dst_entry *dst, unsigned long time)
{
dst->__use++;
dst->lastuse = time;
}
static inline
struct dst_entry * dst_clone(struct dst_entry * dst)
{
@ -177,11 +183,47 @@ struct dst_entry * dst_clone(struct dst_entry * dst)
}
extern void dst_release(struct dst_entry *dst);
static inline void refdst_drop(unsigned long refdst)
{
if (!(refdst & SKB_DST_NOREF))
dst_release((struct dst_entry *)(refdst & SKB_DST_PTRMASK));
}
/**
* skb_dst_drop - drops skb dst
* @skb: buffer
*
* Drops dst reference count if a reference was taken.
*/
static inline void skb_dst_drop(struct sk_buff *skb)
{
if (skb->_skb_dst)
dst_release(skb_dst(skb));
skb->_skb_dst = 0UL;
if (skb->_skb_refdst) {
refdst_drop(skb->_skb_refdst);
skb->_skb_refdst = 0UL;
}
}
static inline void skb_dst_copy(struct sk_buff *nskb, const struct sk_buff *oskb)
{
nskb->_skb_refdst = oskb->_skb_refdst;
if (!(nskb->_skb_refdst & SKB_DST_NOREF))
dst_clone(skb_dst(nskb));
}
/**
* skb_dst_force - makes sure skb dst is refcounted
* @skb: buffer
*
* If dst is not yet refcounted, let's do it
*/
static inline void skb_dst_force(struct sk_buff *skb)
{
if (skb_dst_is_noref(skb)) {
WARN_ON(!rcu_read_lock_held());
skb->_skb_refdst &= ~SKB_DST_NOREF;
dst_clone(skb_dst(skb));
}
}
/* Children define the path of the packet through the

13
include/net/sock.h
View File

@ -600,12 +600,15 @@ static inline int sk_stream_memory_free(struct sock *sk)
/* OOB backlog add */
static inline void __sk_add_backlog(struct sock *sk, struct sk_buff *skb)
{
if (!sk->sk_backlog.tail) {
sk->sk_backlog.head = sk->sk_backlog.tail = skb;
} else {
/* dont let skb dst not refcounted, we are going to leave rcu lock */
skb_dst_force(skb);
if (!sk->sk_backlog.tail)
sk->sk_backlog.head = skb;
else
sk->sk_backlog.tail->next = skb;
sk->sk_backlog.tail = skb;
}
sk->sk_backlog.tail = skb;
skb->next = NULL;
}

3
net/core/dev.c
View File

@ -2052,6 +2052,8 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
* waiting to be sent out; and the qdisc is not running -
* xmit the skb directly.
*/
if (!(dev->priv_flags & IFF_XMIT_DST_RELEASE))
skb_dst_force(skb);
__qdisc_update_bstats(q, skb->len);
if (sch_direct_xmit(skb, q, dev, txq, root_lock))
__qdisc_run(q);
@ -2060,6 +2062,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
rc = NET_XMIT_SUCCESS;
} else {
skb_dst_force(skb);
rc = qdisc_enqueue_root(skb, q);
qdisc_run(q);
}

2
net/core/skbuff.c
View File

@ -520,7 +520,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
new->transport_header = old->transport_header;
new->network_header = old->network_header;
new->mac_header = old->mac_header;
skb_dst_set(new, dst_clone(skb_dst(old)));
skb_dst_copy(new, old);
new->rxhash = old->rxhash;
#ifdef CONFIG_XFRM
new->sp = secpath_get(old->sp);

6
net/core/sock.c
View File

@ -307,6 +307,11 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
*/
skb_len = skb->len;
/* we escape from rcu protected region, make sure we dont leak
* a norefcounted dst
*/
skb_dst_force(skb);
spin_lock_irqsave(&list->lock, flags);
skb->dropcount = atomic_read(&sk->sk_drops);
__skb_queue_tail(list, skb);
@ -1536,6 +1541,7 @@ static void __release_sock(struct sock *sk)
do {
struct sk_buff *next = skb->next;
WARN_ON_ONCE(skb_dst_is_noref(skb));
skb->next = NULL;
sk_backlog_rcv(sk, skb);

6
net/ipv4/icmp.c
View File

@ -587,20 +587,20 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
err = __ip_route_output_key(net, &rt2, &fl);
else {
struct flowi fl2 = {};
struct dst_entry *odst;
unsigned long orefdst;
fl2.fl4_dst = fl.fl4_src;
if (ip_route_output_key(net, &rt2, &fl2))
goto relookup_failed;
/* Ugh! */
odst = skb_dst(skb_in);
orefdst = skb_in->_skb_refdst; /* save old refdst */
err = ip_route_input(skb_in, fl.fl4_dst, fl.fl4_src,
RT_TOS(tos), rt2->u.dst.dev);
dst_release(&rt2->u.dst);
rt2 = skb_rtable(skb_in);
skb_dst_set(skb_in, odst);
skb_in->_skb_refdst = orefdst; /* restore old refdst */
}
if (err)

9
net/ipv4/ip_options.c
View File

@ -601,6 +601,7 @@ int ip_options_rcv_srr(struct sk_buff *skb)
unsigned char *optptr = skb_network_header(skb) + opt->srr;
struct rtable *rt = skb_rtable(skb);
struct rtable *rt2;
unsigned long orefdst;
int err;
if (!opt->srr)
@ -624,16 +625,16 @@ int ip_options_rcv_srr(struct sk_buff *skb)
}
memcpy(&nexthop, &optptr[srrptr-1], 4);
rt = skb_rtable(skb);
orefdst = skb->_skb_refdst;
skb_dst_set(skb, NULL);
err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
rt2 = skb_rtable(skb);
if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
ip_rt_put(rt2);
skb_dst_set(skb, &rt->u.dst);
skb_dst_drop(skb);
skb->_skb_refdst = orefdst;
return -EINVAL;
}
ip_rt_put(rt);
refdst_drop(orefdst);
if (rt2->rt_type != RTN_LOCAL)
break;
/* Superfast 8) loopback forward */

6
net/ipv4/netfilter.c
View File

@ -17,7 +17,7 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
const struct iphdr *iph = ip_hdr(skb);
struct rtable *rt;
struct flowi fl = {};
struct dst_entry *odst;
unsigned long orefdst;
unsigned int hh_len;
unsigned int type;
@ -51,14 +51,14 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
if (ip_route_output_key(net, &rt, &fl) != 0)
return -1;
odst = skb_dst(skb);
orefdst = skb->_skb_refdst;
if (ip_route_input(skb, iph->daddr, iph->saddr,
RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
dst_release(&rt->u.dst);
return -1;
}
dst_release(&rt->u.dst);
dst_release(odst);
refdst_drop(orefdst);
}
if (skb_dst(skb)->error)

2
net/ipv4/route.c
View File

@ -3033,7 +3033,7 @@ int ip_rt_dump(struct sk_buff *skb, struct netlink_callback *cb)
continue;
if (rt_is_expired(rt))
continue;
skb_dst_set(skb, dst_clone(&rt->u.dst));
skb_dst_set_noref(skb, &rt->u.dst);
if (rt_fill_info(net, skb, NETLINK_CB(cb->skb).pid,
cb->nlh->nlmsg_seq, RTM_NEWROUTE,
1, NLM_F_MULTI) <= 0) {

2
net/netfilter/nf_queue.c
View File

@ -9,6 +9,7 @@
#include <linux/rcupdate.h>
#include <net/protocol.h>
#include <net/netfilter/nf_queue.h>
#include <net/dst.h>
#include "nf_internals.h"
@ -170,6 +171,7 @@ static int __nf_queue(struct sk_buff *skb,
dev_hold(physoutdev);
}
#endif
skb_dst_force(skb);
afinfo->saveroute(skb, entry);
status = qh->outfn(entry, queuenum);

4
net/sched/sch_generic.c
View File

@ -26,6 +26,7 @@
#include <linux/list.h>
#include <linux/slab.h>
#include <net/pkt_sched.h>
#include <net/dst.h>
/* Main transmission queue. */
@ -40,6 +41,7 @@
static inline int dev_requeue_skb(struct sk_buff *skb, struct Qdisc *q)
{
skb_dst_force(skb);
q->gso_skb = skb;
q->qstats.requeues++;
q->q.qlen++; /* it's still part of the queue */
@ -179,7 +181,7 @@ static inline int qdisc_restart(struct Qdisc *q)
skb = dequeue_skb(q);
if (unlikely(!skb))
return 0;
WARN_ON_ONCE(skb_dst_is_noref(skb));
root_lock = qdisc_lock(q);
dev = qdisc_dev(q);
txq = netdev_get_tx_queue(dev, skb_get_queue_mapping(skb));