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Merge branch 'inet-add-drop-monitor-support'

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Eric Dumazet says:

====================
inet: add drop monitor support

I recently tried to analyse flakes in ip_defrag selftest.
This failed miserably.

IPv4 and IPv6 reassembly units are causing false kfree_skb()
notifications. It is time to deal with this issue.

First two patches are changing core networking to better
deal with eventual skb frag_list chains, in respect
of kfree_skb/consume_skb status.

Last three patches are adding three new drop reasons,
and make sure skbs that have been reassembled into
a large datagram are no longer viewed as dropped ones.

After this, understanding why ip_defrag selftest is flaky
is possible using standard drop monitoring tools.
====================

Link: https://lore.kernel.org/r/20221029154520.2747444-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2022-10-31 20:14:30 -07:00
commit 6f1a298b2e
8 changed files with 71 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/net/dropreason.h
View File

@ -68,6 +68,9 @@
FN(IP_INADDRERRORS) \
FN(IP_INNOROUTES) \
FN(PKT_TOO_BIG) \
FN(DUP_FRAG) \
FN(FRAG_REASM_TIMEOUT) \
FN(FRAG_TOO_FAR) \
FNe(MAX)
/**
@ -80,6 +83,8 @@ enum skb_drop_reason {
* @SKB_NOT_DROPPED_YET: skb is not dropped yet (used for no-drop case)
*/
SKB_NOT_DROPPED_YET = 0,
/** @SKB_CONSUMED: packet has been consumed */
SKB_CONSUMED,
/** @SKB_DROP_REASON_NOT_SPECIFIED: drop reason is not specified */
SKB_DROP_REASON_NOT_SPECIFIED,
/** @SKB_DROP_REASON_NO_SOCKET: socket not found */
@ -298,6 +303,15 @@ enum skb_drop_reason {
* MTU)
*/
SKB_DROP_REASON_PKT_TOO_BIG,
/** @SKB_DROP_REASON_DUP_FRAG: duplicate fragment */
SKB_DROP_REASON_DUP_FRAG,
/** @SKB_DROP_REASON_FRAG_REASM_TIMEOUT: fragment reassembly timeout */
SKB_DROP_REASON_FRAG_REASM_TIMEOUT,
/**
* @SKB_DROP_REASON_FRAG_TOO_FAR: ipv4 fragment too far.
* (/proc/sys/net/ipv4/ipfrag_max_dist)
*/
SKB_DROP_REASON_FRAG_TOO_FAR,
/**
* @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
* used as a real 'reason'

6
include/net/inet_frag.h
View File

@ -7,6 +7,7 @@
#include <linux/in6.h>
#include <linux/rbtree_types.h>
#include <linux/refcount.h>
#include <net/dropreason.h>
/* Per netns frag queues directory */
struct fqdir {
@ -34,12 +35,14 @@ struct fqdir {
* @INET_FRAG_LAST_IN: final fragment has arrived
* @INET_FRAG_COMPLETE: frag queue has been processed and is due for destruction
* @INET_FRAG_HASH_DEAD: inet_frag_kill() has not removed fq from rhashtable
* @INET_FRAG_DROP: if skbs must be dropped (instead of being consumed)
*/
enum {
INET_FRAG_FIRST_IN = BIT(0),
INET_FRAG_LAST_IN = BIT(1),
INET_FRAG_COMPLETE = BIT(2),
INET_FRAG_HASH_DEAD = BIT(3),
INET_FRAG_DROP = BIT(4),
};
struct frag_v4_compare_key {
@ -139,7 +142,8 @@ void inet_frag_destroy(struct inet_frag_queue *q);
struct inet_frag_queue *inet_frag_find(struct fqdir *fqdir, void *key);
/* Free all skbs in the queue; return the sum of their truesizes. */
unsigned int inet_frag_rbtree_purge(struct rb_root *root);
unsigned int inet_frag_rbtree_purge(struct rb_root *root,
enum skb_drop_reason reason);
static inline void inet_frag_put(struct inet_frag_queue *q)
{

3
include/net/ipv6_frag.h
View File

@ -76,6 +76,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
if (fq->q.flags & INET_FRAG_COMPLETE)
goto out;
fq->q.flags |= INET_FRAG_DROP;
inet_frag_kill(&fq->q);
dev = dev_get_by_index_rcu(net, fq->iif);
@ -101,7 +102,7 @@ ip6frag_expire_frag_queue(struct net *net, struct frag_queue *fq)
spin_unlock(&fq->q.lock);
icmpv6_send(head, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0);
kfree_skb(head);
kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
goto out_rcu_unlock;
out:

30
net/core/skbuff.c
View File

@ -94,6 +94,7 @@ EXPORT_SYMBOL(sysctl_max_skb_frags);
#undef FN
#define FN(reason) [SKB_DROP_REASON_##reason] = #reason,
const char * const drop_reasons[] = {
[SKB_CONSUMED] = "CONSUMED",
DEFINE_DROP_REASON(FN, FN)
};
EXPORT_SYMBOL(drop_reasons);
@ -768,7 +769,7 @@ static void skb_free_head(struct sk_buff *skb)
}
}
static void skb_release_data(struct sk_buff *skb)
static void skb_release_data(struct sk_buff *skb, enum skb_drop_reason reason)
{
struct skb_shared_info *shinfo = skb_shinfo(skb);
int i;
@ -791,7 +792,7 @@ static void skb_release_data(struct sk_buff *skb)
free_head:
if (shinfo->frag_list)
kfree_skb_list(shinfo->frag_list);
kfree_skb_list_reason(shinfo->frag_list, reason);
skb_free_head(skb);
exit:
@ -854,11 +855,11 @@ void skb_release_head_state(struct sk_buff *skb)
}
/* Free everything but the sk_buff shell. */
static void skb_release_all(struct sk_buff *skb)
static void skb_release_all(struct sk_buff *skb, enum skb_drop_reason reason)
{
skb_release_head_state(skb);
if (likely(skb->head))
skb_release_data(skb);
skb_release_data(skb, reason);
}
/**
@ -872,7 +873,7 @@ static void skb_release_all(struct sk_buff *skb)
void __kfree_skb(struct sk_buff *skb)
{
skb_release_all(skb);
skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED);
kfree_skbmem(skb);
}
EXPORT_SYMBOL(__kfree_skb);
@ -894,7 +895,10 @@ kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
trace_kfree_skb(skb, __builtin_return_address(0), reason);
if (reason == SKB_CONSUMED)
trace_consume_skb(skb);
else
trace_kfree_skb(skb, __builtin_return_address(0), reason);
__kfree_skb(skb);
}
EXPORT_SYMBOL(kfree_skb_reason);
@ -1052,7 +1056,7 @@ EXPORT_SYMBOL(consume_skb);
void __consume_stateless_skb(struct sk_buff *skb)
{
trace_consume_skb(skb);
skb_release_data(skb);
skb_release_data(skb, SKB_CONSUMED);
kfree_skbmem(skb);
}
@ -1077,7 +1081,7 @@ static void napi_skb_cache_put(struct sk_buff *skb)
void __kfree_skb_defer(struct sk_buff *skb)
{
skb_release_all(skb);
skb_release_all(skb, SKB_DROP_REASON_NOT_SPECIFIED);
napi_skb_cache_put(skb);
}
@ -1115,7 +1119,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget)
return;
}
skb_release_all(skb);
skb_release_all(skb, SKB_CONSUMED);
napi_skb_cache_put(skb);
}
EXPORT_SYMBOL(napi_consume_skb);
@ -1246,7 +1250,7 @@ EXPORT_SYMBOL_GPL(alloc_skb_for_msg);
*/
struct sk_buff *skb_morph(struct sk_buff *dst, struct sk_buff *src)
{
skb_release_all(dst);
skb_release_all(dst, SKB_CONSUMED);
return __skb_clone(dst, src);
}
EXPORT_SYMBOL_GPL(skb_morph);
@ -1869,7 +1873,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
if (skb_has_frag_list(skb))
skb_clone_fraglist(skb);
skb_release_data(skb);
skb_release_data(skb, SKB_CONSUMED);
} else {
skb_free_head(skb);
}
@ -6209,7 +6213,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
skb_frag_ref(skb, i);
if (skb_has_frag_list(skb))
skb_clone_fraglist(skb);
skb_release_data(skb);
skb_release_data(skb, SKB_CONSUMED);
} else {
/* we can reuse existing recount- all we did was
* relocate values
@ -6352,7 +6356,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
kfree(data);
return -ENOMEM;
}
skb_release_data(skb);
skb_release_data(skb, SKB_CONSUMED);
skb->head = data;
skb->head_frag = 0;

14
net/ipv4/inet_fragment.c
View File

@ -133,6 +133,7 @@ static void inet_frags_free_cb(void *ptr, void *arg)
count = del_timer_sync(&fq->timer) ? 1 : 0;
spin_lock_bh(&fq->lock);
fq->flags |= INET_FRAG_DROP;
if (!(fq->flags & INET_FRAG_COMPLETE)) {
fq->flags |= INET_FRAG_COMPLETE;
count++;
@ -260,7 +261,8 @@ static void inet_frag_destroy_rcu(struct rcu_head *head)
kmem_cache_free(f->frags_cachep, q);
}
unsigned int inet_frag_rbtree_purge(struct rb_root *root)
unsigned int inet_frag_rbtree_purge(struct rb_root *root,
enum skb_drop_reason reason)
{
struct rb_node *p = rb_first(root);
unsigned int sum = 0;
@ -274,7 +276,7 @@ unsigned int inet_frag_rbtree_purge(struct rb_root *root)
struct sk_buff *next = FRAG_CB(skb)->next_frag;
sum += skb->truesize;
kfree_skb(skb);
kfree_skb_reason(skb, reason);
skb = next;
}
}
@ -284,17 +286,21 @@ EXPORT_SYMBOL(inet_frag_rbtree_purge);
void inet_frag_destroy(struct inet_frag_queue *q)
{
struct fqdir *fqdir;
unsigned int sum, sum_truesize = 0;
enum skb_drop_reason reason;
struct inet_frags *f;
struct fqdir *fqdir;
WARN_ON(!(q->flags & INET_FRAG_COMPLETE));
reason = (q->flags & INET_FRAG_DROP) ?
SKB_DROP_REASON_FRAG_REASM_TIMEOUT :
SKB_CONSUMED;
WARN_ON(del_timer(&q->timer) != 0);
/* Release all fragment data. */
fqdir = q->fqdir;
f = fqdir->f;
sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments);
sum_truesize = inet_frag_rbtree_purge(&q->rb_fragments, reason);
sum = sum_truesize + f->qsize;
call_rcu(&q->rcu, inet_frag_destroy_rcu);

19
net/ipv4/ip_fragment.c
View File

@ -153,6 +153,7 @@ static void ip_expire(struct timer_list *t)
if (qp->q.flags & INET_FRAG_COMPLETE)
goto out;
qp->q.flags |= INET_FRAG_DROP;
ipq_kill(qp);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
@ -194,7 +195,7 @@ out:
spin_unlock(&qp->q.lock);
out_rcu_unlock:
rcu_read_unlock();
kfree_skb(head);
kfree_skb_reason(head, SKB_DROP_REASON_FRAG_REASM_TIMEOUT);
ipq_put(qp);
}
@ -254,7 +255,8 @@ static int ip_frag_reinit(struct ipq *qp)
return -ETIMEDOUT;
}
sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments);
sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments,
SKB_DROP_REASON_FRAG_TOO_FAR);
sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
qp->q.flags = 0;
@ -278,10 +280,14 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
struct net_device *dev;
unsigned int fragsize;
int err = -ENOENT;
SKB_DR(reason);
u8 ecn;
if (qp->q.flags & INET_FRAG_COMPLETE)
/* If reassembly is already done, @skb must be a duplicate frag. */
if (qp->q.flags & INET_FRAG_COMPLETE) {
SKB_DR_SET(reason, DUP_FRAG);
goto err;
}
if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
unlikely(ip_frag_too_far(qp)) &&
@ -382,8 +388,9 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
insert_error:
if (err == IPFRAG_DUP) {
kfree_skb(skb);
return -EINVAL;
SKB_DR_SET(reason, DUP_FRAG);
err = -EINVAL;
goto err;
}
err = -EINVAL;
__IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
@ -391,7 +398,7 @@ discard_qp:
inet_frag_kill(&qp->q);
__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
err:
kfree_skb(skb);
kfree_skb_reason(skb, reason);
return err;
}

2
net/ipv6/netfilter/nf_conntrack_reasm.c
View File

@ -253,7 +253,7 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
if (err) {
if (err == IPFRAG_DUP) {
/* No error for duplicates, pretend they got queued. */
kfree_skb(skb);
kfree_skb_reason(skb, SKB_DROP_REASON_DUP_FRAG);
return -EINPROGRESS;
}
goto insert_error;

13
net/ipv6/reassembly.c
View File

@ -112,10 +112,14 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
struct sk_buff *prev_tail;
struct net_device *dev;
int err = -ENOENT;
SKB_DR(reason);
u8 ecn;
if (fq->q.flags & INET_FRAG_COMPLETE)
/* If reassembly is already done, @skb must be a duplicate frag. */
if (fq->q.flags & INET_FRAG_COMPLETE) {
SKB_DR_SET(reason, DUP_FRAG);
goto err;
}
err = -EINVAL;
offset = ntohs(fhdr->frag_off) & ~0x7;
@ -226,8 +230,9 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
insert_error:
if (err == IPFRAG_DUP) {
kfree_skb(skb);
return -EINVAL;
SKB_DR_SET(reason, DUP_FRAG);
err = -EINVAL;
goto err;
}
err = -EINVAL;
__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
@ -237,7 +242,7 @@ discard_fq:
__IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
IPSTATS_MIB_REASMFAILS);
err:
kfree_skb(skb);
kfree_skb_reason(skb, reason);
return err;
}