[PATCH 5.15 075/201] net: skb: use kfree_skb_reason() in tcp_v4_rcv()

Greg Kroah-Hartman
2022-07-27T17:12:54Z

From: Menglong Dong <imagedong@tencent.com>

[ Upstream commit 85125597419aec3aa7b8f3b8713e415f997796f2 ]

Replace kfree_skb() with kfree_skb_reason() in tcp_v4_rcv(). Following
drop reasons are added:

SKB_DROP_REASON_NO_SOCKET
SKB_DROP_REASON_PKT_TOO_SMALL
SKB_DROP_REASON_TCP_CSUM
SKB_DROP_REASON_TCP_FILTER

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_SOCKET

The reason of skb drop is printed too.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/linux/skbuff.h | 4 ++++
include/trace/events/skb.h | 4 ++++
net/ipv4/tcp_ipv4.c | 14 +++++++++++---
3 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 029bc228bcf9..5305af6cc86f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -312,6 +312,10 @@ struct sk_buff;
*/
enum skb_drop_reason {
SKB_DROP_REASON_NOT_SPECIFIED,
+ SKB_DROP_REASON_NO_SOCKET,
+ SKB_DROP_REASON_PKT_TOO_SMALL,
+ SKB_DROP_REASON_TCP_CSUM,
+ SKB_DROP_REASON_TCP_FILTER,
SKB_DROP_REASON_MAX,
};

diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 294c61bbe44b..faa7d068a7bc 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -11,6 +11,10 @@

#define TRACE_SKB_DROP_REASON \
EM(SKB_DROP_REASON_NOT_SPECIFIED, NOT_SPECIFIED) \
+ EM(SKB_DROP_REASON_NO_SOCKET, NO_SOCKET) \
+ EM(SKB_DROP_REASON_PKT_TOO_SMALL, PKT_TOO_SMALL) \
+ EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM) \
+ EM(SKB_DROP_REASON_TCP_FILTER, TCP_FILTER) \
EMe(SKB_DROP_REASON_MAX, MAX)

#undef EM
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index b9a9f288bfa6..d901858aa440 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1976,8 +1976,10 @@ int tcp_v4_rcv(struct sk_buff *skb)
const struct tcphdr *th;
bool refcounted;
struct sock *sk;
+ int drop_reason;
int ret;

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

@@ -1989,8 +1991,10 @@ 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_PKT_TOO_SMALL;
goto bad_packet;
+ }
if (!pskb_may_pull(skb, th->doff * 4))
goto discard_it;

@@ -2093,8 +2097,10 @@ int tcp_v4_rcv(struct sk_buff *skb)

nf_reset_ct(skb);

- if (tcp_filter(sk, skb))
+ if (tcp_filter(sk, skb)) {
+ drop_reason = SKB_DROP_REASON_TCP_FILTER;
goto discard_and_relse;
+ }
th = (const struct tcphdr *)skb->data;
iph = ip_hdr(skb);
tcp_v4_fill_cb(skb, iph, th);
@@ -2131,6 +2137,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
return ret;

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

@@ -2138,6 +2145,7 @@ 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:
@@ -2148,7 +2156,7 @@ int tcp_v4_rcv(struct sk_buff *skb)

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

discard_and_relse:
--
2.35.1