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Subject[PATCH net-next 2/2] net: skb: use kfree_skb_with_reason() in tcp_v4_rcv()
Date
From: Menglong Dong <imagedong@tencent.com>

Replace kfree_skb() with kfree_skb_with_reason() in tcp_v4_rcv().
Following drop reason are added:

SKB_DROP_REASON_NO_SOCK
SKB_DROP_REASON_BAD_PACKET
SKB_DROP_REASON_TCP_CSUM

After this patch, 'kfree_skb' event will print message like this:

$ TASK-PID CPU# ||||| TIMESTAMP FUNCTION
$ | | | ||||| | |
<idle>-0 [000] ..s1. 36.113438: kfree_skb: skbaddr=(____ptrval____) protocol=2048 location=(____ptrval____) reason: NO_SOCK

The reason of skb drop is printed too.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
include/linux/skbuff.h | 3 +++
include/trace/events/skb.h | 3 +++
net/ipv4/tcp_ipv4.c | 10 ++++++++--
3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 3620b3ff2154..f85db6c035d1 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -313,6 +313,9 @@ struct sk_buff;
*/
enum skb_drop_reason {
SKB_DROP_REASON_NOT_SPECIFIED,
+ SKB_DROP_REASON_NO_SOCK,
+ SKB_DROP_REASON_BAD_PACKET,
+ SKB_DROP_REASON_TCP_CSUM,
SKB_DROP_REASON_MAX,
};

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index cab1c08a30cd..b9ea6b4ed7ec 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -11,6 +11,9 @@

#define TRACE_SKB_DROP_REASON \
EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED) \
+ EM(SKB_DROP_REASON_NO_SOCK, NO_SOCK) \
+ EM(SKB_DROP_REASON_BAD_PACKET, BAD_PACKET) \
+ EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM) \
EMe(SKB_DROP_REASON_MAX, HAHA_MAX)

#undef EM
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index ac10e4cdd8d0..03dc4c79b84b 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1971,8 +1971,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
const struct tcphdr *th;
bool refcounted;
struct sock *sk;
+ int drop_reason;
int ret;

+ drop_reason = 0;
if (skb->pkt_type != PACKET_HOST)
goto discard_it;

@@ -1984,8 +1986,10 @@ int tcp_v4_rcv(struct sk_buff *skb)

th = (const struct tcphdr *)skb->data;

- if (unlikely(th->doff < sizeof(struct tcphdr) / 4))
+ if (unlikely(th->doff < sizeof(struct tcphdr) / 4)) {
+ drop_reason = SKB_DROP_REASON_BAD_PACKET;
goto bad_packet;
+ }
if (!pskb_may_pull(skb, th->doff * 4))
goto discard_it;

@@ -2124,6 +2128,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
return ret;

no_tcp_socket:
+ drop_reason = SKB_DROP_REASON_NO_SOCK;
if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
goto discard_it;

@@ -2131,6 +2136,7 @@ int tcp_v4_rcv(struct sk_buff *skb)

if (tcp_checksum_complete(skb)) {
csum_error:
+ drop_reason = SKB_DROP_REASON_TCP_CSUM;
trace_tcp_bad_csum(skb);
__TCP_INC_STATS(net, TCP_MIB_CSUMERRORS);
bad_packet:
@@ -2141,7 +2147,7 @@ int tcp_v4_rcv(struct sk_buff *skb)

discard_it:
/* Discard frame. */
- kfree_skb(skb);
+ kfree_skb_with_reason(skb, drop_reason);
return 0;

discard_and_relse:
--
2.30.2
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