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Date: Fri, 17 Mar 2023 15:55:39 +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: netdev@...r.kernel.org, David Ahern <dsahern@...nel.org>,
Simon Horman <simon.horman@...igine.com>,
Willem de Bruijn <willemb@...gle.com>,
Matthieu Baerts <matthieu.baerts@...sares.net>,
eric.dumazet@...il.com, Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 10/10] tcp: preserve const qualifier in tcp_sk()
We can change tcp_sk() to propagate its argument const qualifier,
thanks to container_of_const().
We have two places where a const sock pointer has to be upgraded
to a write one. We have been using const qualifier for lockless
listeners to clearly identify points where writes could happen.
Add tcp_sk_rw() helper to better document these.
tcp_inbound_md5_hash(), __tcp_grow_window(), tcp_reset_check()
and tcp_rack_reo_wnd() get an additional const qualififer
for their @tp local variables.
smc_check_reset_syn_req() also needs a similar change.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/tcp.h | 10 ++++++----
include/net/tcp.h | 2 +-
net/ipv4/tcp.c | 2 +-
net/ipv4/tcp_input.c | 4 ++--
net/ipv4/tcp_minisocks.c | 5 +++--
net/ipv4/tcp_output.c | 9 +++++++--
net/ipv4/tcp_recovery.c | 2 +-
7 files changed, 21 insertions(+), 13 deletions(-)
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index ca7f05a130d2d14d530207adcc1cc50b7b830c80..b4c08ac86983568a9511258708724da15d0b999e 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -472,10 +472,12 @@ enum tsq_flags {
TCPF_MTU_REDUCED_DEFERRED = (1UL << TCP_MTU_REDUCED_DEFERRED),
};
-static inline struct tcp_sock *tcp_sk(const struct sock *sk)
-{
- return (struct tcp_sock *)sk;
-}
+#define tcp_sk(ptr) container_of_const(ptr, struct tcp_sock, inet_conn.icsk_inet.sk)
+
+/* Variant of tcp_sk() upgrading a const sock to a read/write tcp socket.
+ * Used in context of (lockless) tcp listeners.
+ */
+#define tcp_sk_rw(ptr) container_of(ptr, struct tcp_sock, inet_conn.icsk_inet.sk)
struct tcp_timewait_sock {
struct inet_timewait_sock tw_sk;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index db9f828e9d1ee4546951a408935b6c5f90851a93..a0a91a988272710470cd20f22e02e49476513239 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -529,7 +529,7 @@ static inline void tcp_synq_overflow(const struct sock *sk)
last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
if (!time_between32(now, last_overflow, last_overflow + HZ))
- WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now);
+ WRITE_ONCE(tcp_sk_rw(sk)->rx_opt.ts_recent_stamp, now);
}
/* syncookies: no recent synqueue overflow on this listening socket? */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 01569de651b65aa5641fb0c06e0fb81dc40cd85a..fd68d49490f2849a41397be5bf78dbf07cadd7ff 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4570,7 +4570,7 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
const __u8 *hash_location = NULL;
struct tcp_md5sig_key *hash_expected;
const struct tcphdr *th = tcp_hdr(skb);
- struct tcp_sock *tp = tcp_sk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
int genhash, l3index;
u8 newhash[16];
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 754ddbe0577f139d209032b4f15787392fe9a1d5..2b75cd9e2e92ea1b6e8e16485a8792790a905ade 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -458,7 +458,7 @@ static void tcp_sndbuf_expand(struct sock *sk)
static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb,
unsigned int skbtruesize)
{
- struct tcp_sock *tp = tcp_sk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
/* Optimize this! */
int truesize = tcp_win_from_space(sk, skbtruesize) >> 1;
int window = tcp_win_from_space(sk, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2])) >> 1;
@@ -5693,7 +5693,7 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *t
*/
static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
{
- struct tcp_sock *tp = tcp_sk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
(1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 9a7ef7732c24c94d4a01d5911ebe51f21371a457..dac0d62120e623ad3f206daa1785eddb39452fd6 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -463,7 +463,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
}
EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
-static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
+static void smc_check_reset_syn_req(const struct tcp_sock *oldtp,
struct request_sock *req,
struct tcp_sock *newtp)
{
@@ -492,7 +492,8 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
const struct inet_request_sock *ireq = inet_rsk(req);
struct tcp_request_sock *treq = tcp_rsk(req);
struct inet_connection_sock *newicsk;
- struct tcp_sock *oldtp, *newtp;
+ const struct tcp_sock *oldtp;
+ struct tcp_sock *newtp;
u32 seq;
if (!newsk)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index f7e00d90a7304cdbaee493d994c6ab1063392d34..b9e07f1951419c3a2858eea0c26f604b96f0be70 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4127,8 +4127,13 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
if (!res) {
TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
- if (unlikely(tcp_passive_fastopen(sk)))
- tcp_sk(sk)->total_retrans++;
+ if (unlikely(tcp_passive_fastopen(sk))) {
+ /* sk has const attribute because listeners are lockless.
+ * However in this case, we are dealing with a passive fastopen
+ * socket thus we can change total_retrans value.
+ */
+ tcp_sk_rw(sk)->total_retrans++;
+ }
trace_tcp_retransmit_synack(sk, req);
}
return res;
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index 50abaa941387d3e7328b6859ea5118937fc12be4..acf4869c5d3b568227aca71d95a765493e452a85 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -4,7 +4,7 @@
static u32 tcp_rack_reo_wnd(const struct sock *sk)
{
- struct tcp_sock *tp = tcp_sk(sk);
+ const struct tcp_sock *tp = tcp_sk(sk);
if (!tp->reord_seen) {
/* If reordering has not been observed, be aggressive during
--
2.40.0.rc2.332.ga46443480c-goog
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