[PATCH net-next v4 5/8] net: tcp: add skb drop reasons to tcp connect requesting

From: menglong8 . dong
Date: Fri Jun 17 2022 - 06:06:39 EST

From: Menglong Dong <imagedong@xxxxxxxxxxx>

In order to get skb drop reasons during tcp connect requesting code path,
we have to pass the pointer of the 'reason' as a new function argument of
conn_request() in 'struct inet_connection_sock_af_ops'. As the return
value of conn_request() can be positive or negative or 0, it's not
flexible to make it return drop reasons.

As the return value of tcp_conn_request() is 0, so we can treat it as bool
and make it return the skb drop reasons.

The new drop reasons 'LISTENOVERFLOWS' and 'TCP_REQQFULLDROP' are added,
which are used for 'accept queue' and 'request queue' full.

Reviewed-by: Jiang Biao <benbjiang@xxxxxxxxxxx>
Reviewed-by: Hao Peng <flyingpeng@xxxxxxxxxxx>
Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
--
v2:
- fix compile error reported by kernel test rebot
---
include/net/dropreason.h | 10 ++++++++++
include/net/inet_connection_sock.h | 3 ++-
include/net/tcp.h | 9 +++++----
net/dccp/dccp.h | 3 ++-
net/dccp/input.c | 3 ++-
net/dccp/ipv4.c | 3 ++-
net/dccp/ipv6.c | 5 +++--
net/ipv4/tcp_input.c | 22 ++++++++++++++--------
net/ipv4/tcp_ipv4.c | 9 ++++++---
net/ipv6/tcp_ipv6.c | 12 ++++++++----
net/mptcp/subflow.c | 8 +++++---
11 files changed, 59 insertions(+), 28 deletions(-)

diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index 3c6f1e299c35..74512e60ab12 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -236,6 +236,16 @@ enum skb_drop_reason {
* skb in its receive or send queue are all dropped
*/
SKB_DROP_REASON_SOCKET_DESTROYED,
+ /**
+ * @SKB_DROP_REASON_LISTENOVERFLOWS: accept queue of the listen
+ * socket is full, corresponding to LINUX_MIB_LISTENOVERFLOWS
+ */
+ SKB_DROP_REASON_LISTENOVERFLOWS,
+ /**
+ * @SKB_DROP_REASON_TCP_REQQFULLDROP: request queue of the listen
+ * socket is full, corresponding to LINUX_MIB_TCPREQQFULLDROP
+ */
+ SKB_DROP_REASON_TCP_REQQFULLDROP,
/**
* @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
* used as a real 'reason'
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index 077cd730ce2f..7717c59ab3d7 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -37,7 +37,8 @@ struct inet_connection_sock_af_ops {
void (*send_check)(struct sock *sk, struct sk_buff *skb);
int (*rebuild_header)(struct sock *sk);
void (*sk_rx_dst_set)(struct sock *sk, const struct sk_buff *skb);
- int (*conn_request)(struct sock *sk, struct sk_buff *skb);
+ int (*conn_request)(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason);
struct sock *(*syn_recv_sock)(const struct sock *sk, struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 1e99f5c61f84..16da150150c3 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -443,7 +443,8 @@ void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
void tcp_v4_mtu_reduced(struct sock *sk);
void tcp_req_err(struct sock *sk, u32 seq, bool abort);
void tcp_ld_RTO_revert(struct sock *sk, u32 seq);
-int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
+int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason);
struct sock *tcp_create_openreq_child(const struct sock *sk,
struct request_sock *req,
struct sk_buff *skb);
@@ -2034,9 +2035,9 @@ void tcp4_proc_exit(void);
#endif

int tcp_rtx_synack(const struct sock *sk, struct request_sock *req);
-int tcp_conn_request(struct request_sock_ops *rsk_ops,
- const struct tcp_request_sock_ops *af_ops,
- struct sock *sk, struct sk_buff *skb);
+enum skb_drop_reason tcp_conn_request(struct request_sock_ops *rsk_ops,
+ const struct tcp_request_sock_ops *af_ops,
+ struct sock *sk, struct sk_buff *skb);

/* TCP af-specific functions */
struct tcp_sock_af_ops {
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 7dfc00c9fb32..8c1241ae8449 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -255,7 +255,8 @@ void dccp_done(struct sock *sk);
int dccp_reqsk_init(struct request_sock *rq, struct dccp_sock const *dp,
struct sk_buff const *skb);

-int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
+int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason);

struct sock *dccp_create_openreq_child(const struct sock *sk,
const struct request_sock *req,
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 2cbb757a894f..e12baa56ca59 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -576,6 +576,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
const int old_state = sk->sk_state;
bool acceptable;
int queued = 0;
+ SKB_DR(reason);

/*
* Step 3: Process LISTEN state
@@ -606,7 +607,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
*/
rcu_read_lock();
local_bh_disable();
- acceptable = inet_csk(sk)->icsk_af_ops->conn_request(sk, skb) >= 0;
+ acceptable = inet_csk(sk)->icsk_af_ops->conn_request(sk, skb, &reason) >= 0;
local_bh_enable();
rcu_read_unlock();
if (!acceptable)
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index da6e3b20cd75..b0e8fcabf93b 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -581,7 +581,8 @@ static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
.syn_ack_timeout = dccp_syn_ack_timeout,
};

-int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
struct inet_request_sock *ireq;
struct request_sock *req;
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index fd44638ec16b..f01d6a05c7bf 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -314,7 +314,8 @@ static struct request_sock_ops dccp6_request_sock_ops = {
.syn_ack_timeout = dccp_syn_ack_timeout,
};

-static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
+static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
struct request_sock *req;
struct dccp_request_sock *dreq;
@@ -324,7 +325,7 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);

if (skb->protocol == htons(ETH_P_IP))
- return dccp_v4_conn_request(sk, skb);
+ return dccp_v4_conn_request(sk, skb, reason);

if (!ipv6_unicast_destination(skb))
return 0; /* discard, don't send a reset here */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2e2a9ece9af2..8617e7a8f841 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6453,13 +6453,14 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
*/
rcu_read_lock();
local_bh_disable();
- acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;
+ reason = SKB_NOT_DROPPED_YET;
+ acceptable = icsk->icsk_af_ops->conn_request(sk, skb, &reason) >= 0;
local_bh_enable();
rcu_read_unlock();

if (!acceptable)
return 1;
- consume_skb(skb);
+ kfree_skb_reason(skb, reason);
return 0;
}
SKB_DR_SET(reason, TCP_FLAGS);
@@ -6879,9 +6880,9 @@ u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
}
EXPORT_SYMBOL_GPL(tcp_get_syncookie_mss);

-int tcp_conn_request(struct request_sock_ops *rsk_ops,
- const struct tcp_request_sock_ops *af_ops,
- struct sock *sk, struct sk_buff *skb)
+enum skb_drop_reason tcp_conn_request(struct request_sock_ops *rsk_ops,
+ const struct tcp_request_sock_ops *af_ops,
+ struct sock *sk, struct sk_buff *skb)
{
struct tcp_fastopen_cookie foc = { .len = -1 };
__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
@@ -6893,6 +6894,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
bool want_cookie = false;
struct dst_entry *dst;
struct flowi fl;
+ SKB_DR(reason);

/* TW buckets are converted to open requests without
* limitations, they conserve resources and peer is
@@ -6901,12 +6903,15 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
if ((net->ipv4.sysctl_tcp_syncookies == 2 ||
inet_csk_reqsk_queue_is_full(sk)) && !isn) {
want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
- if (!want_cookie)
+ if (!want_cookie) {
+ SKB_DR_SET(reason, TCP_REQQFULLDROP);
goto drop;
+ }
}

if (sk_acceptq_is_full(sk)) {
NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
+ SKB_DR_SET(reason, LISTENOVERFLOWS);
goto drop;
}

@@ -6962,6 +6967,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
*/
pr_drop_req(req, ntohs(tcp_hdr(skb)->source),
rsk_ops->family);
+ SKB_DR_SET(reason, TCP_REQQFULLDROP);
goto drop_and_release;
}

@@ -7014,7 +7020,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
}
}
reqsk_put(req);
- return 0;
+ return SKB_NOT_DROPPED_YET;

drop_and_release:
dst_release(dst);
@@ -7022,6 +7028,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
__reqsk_free(req);
drop:
tcp_listendrop(sk);
- return 0;
+ return reason;
}
EXPORT_SYMBOL(tcp_conn_request);
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index fe8f23b95d32..e1064273062a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1458,17 +1458,20 @@ const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
.send_synack = tcp_v4_send_synack,
};

-int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
/* Never answer to SYNs send to broadcast or multicast */
if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
goto drop;

- return tcp_conn_request(&tcp_request_sock_ops,
- &tcp_request_sock_ipv4_ops, sk, skb);
+ *reason = tcp_conn_request(&tcp_request_sock_ops,
+ &tcp_request_sock_ipv4_ops, sk, skb);
+ return *reason;

drop:
tcp_listendrop(sk);
+ *reason = SKB_DROP_REASON_IP_INADDRERRORS;
return 0;
}
EXPORT_SYMBOL(tcp_v4_conn_request);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index f37dd4aa91c6..dbe356a166c5 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1148,24 +1148,28 @@ u16 tcp_v6_get_syncookie(struct sock *sk, struct ipv6hdr *iph,
return mss;
}

-static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
+static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
if (skb->protocol == htons(ETH_P_IP))
- return tcp_v4_conn_request(sk, skb);
+ return tcp_v4_conn_request(sk, skb, reason);

if (!ipv6_unicast_destination(skb))
goto drop;

if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
__IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
+ *reason = SKB_DROP_REASON_IP_INADDRERRORS;
return 0;
}

- return tcp_conn_request(&tcp6_request_sock_ops,
- &tcp_request_sock_ipv6_ops, sk, skb);
+ *reason = tcp_conn_request(&tcp6_request_sock_ops,
+ &tcp_request_sock_ipv6_ops, sk, skb);
+ return *reason;

drop:
tcp_listendrop(sk);
+ *reason = SKB_DROP_REASON_IP_INADDRERRORS;
return 0; /* don't send reset */
}

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 8841e8cd9ad8..5a1d05c3a1ef 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -532,7 +532,8 @@ static int subflow_v6_rebuild_header(struct sock *sk)
struct request_sock_ops mptcp_subflow_request_sock_ops;
static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;

-static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);

@@ -556,14 +557,15 @@ static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
static struct proto tcpv6_prot_override;

-static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
+static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb,
+ enum skb_drop_reason *reason)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);

pr_debug("subflow=%p", subflow);

if (skb->protocol == htons(ETH_P_IP))
- return subflow_v4_conn_request(sk, skb);
+ return subflow_v4_conn_request(sk, skb, reason);

if (!ipv6_unicast_destination(skb))
goto drop;
--
2.36.1