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Message-ID: <20240407093322.3172088-3-edumazet@google.com>
Date: Sun, 7 Apr 2024 09:33:22 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Neal Cardwell <ncardwell@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/2] tcp: replace TCP_SKB_CB(skb)->tcp_tw_isn with a
per-cpu field
TCP can transform a TIMEWAIT socket into a SYN_RECV one from
a SYN packet, and the ISN of the SYNACK packet is normally
generated using TIMEWAIT tw_snd_nxt :
tcp_timewait_state_process()
...
u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
if (isn == 0)
isn++;
TCP_SKB_CB(skb)->tcp_tw_isn = isn;
return TCP_TW_SYN;
This SYN packet also bypasses normal checks against listen queue
being full or not.
tcp_conn_request()
...
__u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
...
/* TW buckets are converted to open requests without
* limitations, they conserve resources and peer is
* evidently real one.
*/
if ((syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) && !isn) {
want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
if (!want_cookie)
goto drop;
}
This was using TCP_SKB_CB(skb)->tcp_tw_isn field in skb.
Unfortunately this field has been accidentally cleared
after the call to tcp_timewait_state_process() returning
TCP_TW_SYN.
Using a field in TCP_SKB_CB(skb) for a temporary state
is overkill.
Switch instead to a per-cpu variable.
As a bonus, we do not have to clear tcp_tw_isn in TCP receive
fast path.
It is temporarily set then cleared only in the TCP_TW_SYN dance.
Fixes: 4ad19de8774e ("net: tcp6: fix double call of tcp_v6_fill_cb()")
Fixes: eeea10b83a13 ("tcp: add tcp_v4_fill_cb()/tcp_v4_restore_cb()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/tcp.h | 10 +++++-----
net/ipv4/tcp.c | 3 +++
net/ipv4/tcp_input.c | 26 ++++++++++++++++----------
net/ipv4/tcp_ipv4.c | 5 +++--
net/ipv4/tcp_minisocks.c | 4 ++--
net/ipv6/tcp_ipv6.c | 5 +++--
6 files changed, 32 insertions(+), 21 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index fa0ab77acee23654b22e97615de983fc04eee319..ba6c5ae86e228a1633feaf39b0f1e053c3832b08 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -52,6 +52,8 @@ extern struct inet_hashinfo tcp_hashinfo;
DECLARE_PER_CPU(unsigned int, tcp_orphan_count);
int tcp_orphan_count_sum(void);
+DECLARE_PER_CPU(u32, tcp_tw_isn);
+
void tcp_time_wait(struct sock *sk, int state, int timeo);
#define MAX_TCP_HEADER L1_CACHE_ALIGN(128 + MAX_HEADER)
@@ -392,7 +394,8 @@ 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);
+ const struct tcphdr *th,
+ u32 *tw_isn);
struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
struct request_sock *req, bool fastopen,
bool *lost_race);
@@ -935,13 +938,10 @@ struct tcp_skb_cb {
__u32 seq; /* Starting sequence number */
__u32 end_seq; /* SEQ + FIN + SYN + datalen */
union {
- /* Note : tcp_tw_isn is used in input path only
- * (isn chosen by tcp_timewait_state_process())
- *
+ /* Note :
* tcp_gso_segs/size are used in write queue only,
* cf tcp_skb_pcount()/tcp_skb_mss()
*/
- __u32 tcp_tw_isn;
struct {
u16 tcp_gso_segs;
u16 tcp_gso_size;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 92ee60492314a1483cfbfa2f73d32fcad5632773..6cb5b9f74c94b72fec1d6a3cc8e6dc75bd61ba2f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -290,6 +290,9 @@ enum {
DEFINE_PER_CPU(unsigned int, tcp_orphan_count);
EXPORT_PER_CPU_SYMBOL_GPL(tcp_orphan_count);
+DEFINE_PER_CPU(u32, tcp_tw_isn);
+EXPORT_PER_CPU_SYMBOL_GPL(tcp_tw_isn);
+
long sysctl_tcp_mem[3] __read_mostly;
EXPORT_SYMBOL(sysctl_tcp_mem);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 48c275e6ef02bfc5dd98f0878c752841f949c714..5a45a0923a1f058cdc80255be0f76a71fd102d4d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -7097,7 +7097,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
struct sock *sk, struct sk_buff *skb)
{
struct tcp_fastopen_cookie foc = { .len = -1 };
- __u32 isn = TCP_SKB_CB(skb)->tcp_tw_isn;
struct tcp_options_received tmp_opt;
struct tcp_sock *tp = tcp_sk(sk);
struct net *net = sock_net(sk);
@@ -7107,21 +7106,28 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
struct dst_entry *dst;
struct flowi fl;
u8 syncookies;
+ u32 isn;
#ifdef CONFIG_TCP_AO
const struct tcp_ao_hdr *aoh;
#endif
- syncookies = READ_ONCE(net->ipv4.sysctl_tcp_syncookies);
+ isn = __this_cpu_read(tcp_tw_isn);
+ if (isn) {
+ /* TW buckets are converted to open requests without
+ * limitations, they conserve resources and peer is
+ * evidently real one.
+ */
+ __this_cpu_write(tcp_tw_isn, 0);
+ } else {
+ syncookies = READ_ONCE(net->ipv4.sysctl_tcp_syncookies);
- /* TW buckets are converted to open requests without
- * limitations, they conserve resources and peer is
- * evidently real one.
- */
- if ((syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) && !isn) {
- want_cookie = tcp_syn_flood_action(sk, rsk_ops->slab_name);
- if (!want_cookie)
- goto drop;
+ if (syncookies == 2 || inet_csk_reqsk_queue_is_full(sk)) {
+ want_cookie = tcp_syn_flood_action(sk,
+ rsk_ops->slab_name);
+ if (!want_cookie)
+ goto drop;
+ }
}
if (sk_acceptq_is_full(sk)) {
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 81e2f05c244d1671980a34bb756f528f3e6debcc..1e650ec71d2fe5198b9dad9e6ea9c5eaf868277f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2146,7 +2146,6 @@ static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
skb->len - th->doff * 4);
TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
- TCP_SKB_CB(skb)->tcp_tw_isn = 0;
TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
TCP_SKB_CB(skb)->sacked = 0;
TCP_SKB_CB(skb)->has_rxtstamp =
@@ -2168,6 +2167,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
bool refcounted;
struct sock *sk;
int ret;
+ u32 isn;
drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
if (skb->pkt_type != PACKET_HOST)
@@ -2383,7 +2383,7 @@ 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, &isn)) {
case TCP_TW_SYN: {
struct sock *sk2 = inet_lookup_listener(net,
net->ipv4.tcp_death_row.hashinfo,
@@ -2397,6 +2397,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
sk = sk2;
tcp_v4_restore_cb(skb);
refcounted = false;
+ __this_cpu_write(tcp_tw_isn, isn);
goto process;
}
}
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 5b21a07ddf9aa5593d21cb856f0e0ea2f45b1eef..f53c7ada2ace4219917e75f806f39a00d5ab0123 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -95,7 +95,7 @@ static void twsk_rcv_nxt_update(struct tcp_timewait_sock *tcptw, u32 seq)
*/
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, u32 *tw_isn)
{
struct tcp_options_received tmp_opt;
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
@@ -228,7 +228,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
if (isn == 0)
isn++;
- TCP_SKB_CB(skb)->tcp_tw_isn = isn;
+ *tw_isn = isn;
return TCP_TW_SYN;
}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5141f7033abd8bb03bc4e162066ca4befe343bdc..3aa9da5c9a669d2754b421cfb704ad28def5a748 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1741,7 +1741,6 @@ static void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
skb->len - th->doff*4);
TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
- TCP_SKB_CB(skb)->tcp_tw_isn = 0;
TCP_SKB_CB(skb)->ip_dsfield = ipv6_get_dsfield(hdr);
TCP_SKB_CB(skb)->sacked = 0;
TCP_SKB_CB(skb)->has_rxtstamp =
@@ -1758,6 +1757,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
bool refcounted;
struct sock *sk;
int ret;
+ u32 isn;
struct net *net = dev_net(skb->dev);
drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
@@ -1967,7 +1967,7 @@ 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, &isn)) {
case TCP_TW_SYN:
{
struct sock *sk2;
@@ -1985,6 +1985,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
sk = sk2;
tcp_v6_restore_cb(skb);
refcounted = false;
+ __this_cpu_write(tcp_tw_isn, isn);
goto process;
}
}
--
2.44.0.478.gd926399ef9-goog
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