[PATCH net-next v3 7/9] net: tcp: add skb drop reasons to tcp tw code path
From: menglong8 . dong
Date: Thu Jun 09 2022 - 23:45:37 EST
From: Menglong Dong <imagedong@xxxxxxxxxxx>
In order to get the reasons of skb drops, add a function argument of
type 'enum skb_drop_reason *reason' to tcp_timewait_state_process().
In the origin code, all packets to time-wait socket are treated as
dropping with kfree_skb(), which can make users confused. Therefore,
we use consume_skb() for the skbs that are 'good'. We can check the
value of 'reason' to decide use kfree_skb() or consume_skb().
The new reason 'TIMEWAIT' is added for the case that the skb is dropped
as the socket in time-wait state.
Reviewed-by: Jiang Biao <benbjiang@xxxxxxxxxxx>
Reviewed-by: Hao Peng <flyingpeng@xxxxxxxxxxx>
Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
v2:
- skb is not freed on TCP_TW_ACK and 'ret' is not initizalized, fix
it (Eric Dumazet)
---
include/net/dropreason.h | 6 ++++++
include/net/tcp.h | 7 ++++---
net/ipv4/tcp_ipv4.c | 9 ++++++++-
net/ipv4/tcp_minisocks.c | 24 ++++++++++++++++++++----
net/ipv6/tcp_ipv6.c | 8 +++++++-
5 files changed, 45 insertions(+), 9 deletions(-)
diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index 86e89d3022b5..3c6f8e0f7f16 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -258,6 +258,12 @@ enum skb_drop_reason {
* socket is full, corresponding to LINUX_MIB_TCPREQQFULLDROP
*/
SKB_DROP_REASON_TCP_REQQFULLDROP,
+ /**
+ * @SKB_DROP_REASON_TIMEWAIT: socket is in time-wait state and all
+ * packet that received will be treated as 'drop', except a good
+ * 'SYN' packet
+ */
+ SKB_DROP_REASON_TIMEWAIT,
/**
* @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
* used as a real 'reason'
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 082dd0627e2e..88217b8d95ac 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -380,9 +380,10 @@ enum tcp_tw_status {
};
-enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
- struct sk_buff *skb,
- const struct tcphdr *th);
+enum tcp_tw_status
+tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
+ const struct tcphdr *th,
+ enum skb_drop_reason *reason);
struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
struct request_sock *req, bool fastopen,
bool *lost_race);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 804fc5e0203e..e7bd2f410a4a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2134,7 +2134,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
inet_twsk_put(inet_twsk(sk));
goto csum_error;
}
- switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) {
+ switch (tcp_timewait_state_process(inet_twsk(sk), skb, th,
+ &drop_reason)) {
case TCP_TW_SYN: {
struct sock *sk2 = inet_lookup_listener(dev_net(skb->dev),
&tcp_hashinfo, skb,
@@ -2150,11 +2151,17 @@ int tcp_v4_rcv(struct sk_buff *skb)
refcounted = false;
goto process;
}
+ /* TCP_FLAGS or NO_SOCKET? */
+ SKB_DR_SET(drop_reason, TCP_FLAGS);
}
/* to ACK */
fallthrough;
case TCP_TW_ACK:
tcp_v4_timewait_ack(sk, skb);
+ if (!drop_reason) {
+ consume_skb(skb);
+ return 0;
+ }
break;
case TCP_TW_RST:
tcp_v4_send_reset(sk, skb);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 1a21018f6f64..329724118b7f 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -83,13 +83,15 @@ tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw,
*/
enum tcp_tw_status
tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
- const struct tcphdr *th)
+ const struct tcphdr *th,
+ enum skb_drop_reason *reason)
{
struct tcp_options_received tmp_opt;
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
bool paws_reject = false;
tmp_opt.saw_tstamp = 0;
+ *reason = SKB_DROP_REASON_NOT_SPECIFIED;
if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
tcp_parse_options(twsk_net(tw), skb, &tmp_opt, 0, NULL);
@@ -113,11 +115,16 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
return tcp_timewait_check_oow_rate_limit(
tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2);
- if (th->rst)
+ if (th->rst) {
+ SKB_DR_SET(*reason, TCP_RESET);
goto kill;
+ }
- if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
+ if (th->syn && !before(TCP_SKB_CB(skb)->seq,
+ tcptw->tw_rcv_nxt)) {
+ SKB_DR_SET(*reason, TCP_FLAGS);
return TCP_TW_RST;
+ }
/* Dup ACK? */
if (!th->ack ||
@@ -143,6 +150,9 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
}
inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
+
+ /* skb should be free normally on this case. */
+ *reason = SKB_NOT_DROPPED_YET;
return TCP_TW_ACK;
}
@@ -174,6 +184,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
* protocol bug yet.
*/
if (twsk_net(tw)->ipv4.sysctl_tcp_rfc1337 == 0) {
+ SKB_DR_SET(*reason, TCP_RESET);
kill:
inet_twsk_deschedule_put(tw);
return TCP_TW_SUCCESS;
@@ -216,11 +227,14 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
if (isn == 0)
isn++;
TCP_SKB_CB(skb)->tcp_tw_isn = isn;
+ *reason = SKB_NOT_DROPPED_YET;
return TCP_TW_SYN;
}
- if (paws_reject)
+ if (paws_reject) {
+ SKB_DR_SET(*reason, TCP_RFC7323_PAWS);
__NET_INC_STATS(twsk_net(tw), LINUX_MIB_PAWSESTABREJECTED);
+ }
if (!th->rst) {
/* In this case we must reset the TIMEWAIT timer.
@@ -232,9 +246,11 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
if (paws_reject || th->ack)
inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
+ SKB_DR_OR(*reason, TIMEWAIT);
return tcp_timewait_check_oow_rate_limit(
tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT);
}
+ SKB_DR_SET(*reason, TCP_RESET);
inet_twsk_put(tw);
return TCP_TW_SUCCESS;
}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 0d2ba9d90529..41551a3b679b 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1795,7 +1795,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
goto csum_error;
}
- switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) {
+ switch (tcp_timewait_state_process(inet_twsk(sk), skb, th,
+ &drop_reason)) {
case TCP_TW_SYN:
{
struct sock *sk2;
@@ -1815,11 +1816,16 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
refcounted = false;
goto process;
}
+ SKB_DR_SET(drop_reason, TCP_FLAGS);
}
/* to ACK */
fallthrough;
case TCP_TW_ACK:
tcp_v6_timewait_ack(sk, skb);
+ if (!drop_reason) {
+ consume_skb(skb);
+ return 0;
+ }
break;
case TCP_TW_RST:
tcp_v6_send_reset(sk, skb);
--
2.36.1