diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst
index 4a010a7cde7f8085db5ba6f1b9af53e9e5223cd5..82f2117cf2b36a834e5e391feda0210d916bff8b 100644
--- a/Documentation/networking/ip-sysctl.rst
+++ b/Documentation/networking/ip-sysctl.rst
@@ -321,6 +321,7 @@ tcp_abort_on_overflow - BOOLEAN
option can harm clients of your server.
tcp_adv_win_scale - INTEGER
+ Obsolete since linux-6.6
Count buffering overhead as bytes/2^tcp_adv_win_scale
(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
if it is <= 0.
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index b4c08ac86983568a9511258708724da15d0b999e..fbcb0ce13171d46aa3697abcd48482b08e78e5e0 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -172,6 +172,8 @@ static inline struct tcp_request_sock *tcp_rsk(const struct request_sock *req)
return (struct tcp_request_sock *)req;
}
+#define TCP_RMEM_TO_WIN_SCALE 8
+
struct tcp_sock {
/* inet_connection_sock has to be the first member of tcp_sock */
struct inet_connection_sock inet_conn;
@@ -238,7 +240,7 @@ struct tcp_sock {
u32 window_clamp; /* Maximal window to advertise */
u32 rcv_ssthresh; /* Current window clamp */
-
+ u8 scaling_ratio; /* see tcp_win_from_space() */
/* Information of the most recently (s)acked skb */
struct tcp_rack {
u64 mstamp; /* (Re)sent time of the skb */
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index f003747181593559a4efe1838be719d445417041..7a41c4791536732005cedbb80c223b86aa43249e 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -152,7 +152,7 @@ struct netns_ipv4 {
u8 sysctl_tcp_abort_on_overflow;
u8 sysctl_tcp_fack; /* obsolete */
int sysctl_tcp_max_reordering;
- int sysctl_tcp_adv_win_scale;
+ int sysctl_tcp_adv_win_scale; /* obsolete */
u8 sysctl_tcp_dsack;
u8 sysctl_tcp_app_win;
u8 sysctl_tcp_frto;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 226bce6d1e8c30185260baadec449b67323db91c..2104a71c75ba7eee40612395be4103ae370b3c03 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1434,11 +1434,27 @@ void tcp_select_initial_window(const struct sock *sk, int __space,
static inline int tcp_win_from_space(const struct sock *sk, int space)
{
- int tcp_adv_win_scale = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale);
+ s64 scaled_space = (s64)space * tcp_sk(sk)->scaling_ratio;
- return tcp_adv_win_scale <= 0 ?
- (space>>(-tcp_adv_win_scale)) :
- space - (space>>tcp_adv_win_scale);
+ return scaled_space >> TCP_RMEM_TO_WIN_SCALE;
+}
+
+/* inverse of tcp_win_from_space() */
+static inline int tcp_space_from_win(const struct sock *sk, int win)
+{
+ u64 val = (u64)win << TCP_RMEM_TO_WIN_SCALE;
+
+ do_div(val, tcp_sk(sk)->scaling_ratio);
+ return val;
+}
+
+static inline void tcp_scaling_ratio_init(struct sock *sk)
+{
+ /* Assume a conservative default of 1200 bytes of payload per 4K page.
+ * This may be adjusted later in tcp_measure_rcv_mss().
+ */
+ tcp_sk(sk)->scaling_ratio = (1200 << TCP_RMEM_TO_WIN_SCALE) /
+ SKB_TRUESIZE(4096);
}
/* Note: caller must be prepared to deal with negative returns */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e03e08745308189c9d64509c2cff94da56c86a0c..88f4ebab12acc11d5f3feb6b13974a0b8e565671 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -457,6 +457,7 @@ void tcp_init_sock(struct sock *sk)
WRITE_ONCE(sk->sk_sndbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_wmem[1]));
WRITE_ONCE(sk->sk_rcvbuf, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[1]));
+ tcp_scaling_ratio_init(sk);
set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
sk_sockets_allocated_inc(sk);
@@ -1700,7 +1701,7 @@ EXPORT_SYMBOL(tcp_peek_len);
/* Make sure sk_rcvbuf is big enough to satisfy SO_RCVLOWAT hint */
int tcp_set_rcvlowat(struct sock *sk, int val)
{
- int cap;
+ int space, cap;
if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
cap = sk->sk_rcvbuf >> 1;
@@ -1715,10 +1716,10 @@ int tcp_set_rcvlowat(struct sock *sk, int val)
if (sk->sk_userlocks & SOCK_RCVBUF_LOCK)
return 0;
- val <<= 1;
- if (val > sk->sk_rcvbuf) {
- WRITE_ONCE(sk->sk_rcvbuf, val);
- tcp_sk(sk)->window_clamp = tcp_win_from_space(sk, val);
+ space = tcp_space_from_win(sk, val);
+ if (space > sk->sk_rcvbuf) {
+ WRITE_ONCE(sk->sk_rcvbuf, space);
+ tcp_sk(sk)->window_clamp = val;
}
return 0;
}
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 57c8af1859c16eba5e952a23ea959b628006f9c1..3cd92035e0902298baa8afd89ae5edcbfce300e5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -237,6 +237,16 @@ static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb)
*/
len = skb_shinfo(skb)->gso_size ? : skb->len;
if (len >= icsk->icsk_ack.rcv_mss) {
+ /* Note: divides are still a bit expensive.
+ * For the moment, only adjust scaling_ratio
+ * when we update icsk_ack.rcv_mss.
+ */
+ if (unlikely(len != icsk->icsk_ack.rcv_mss)) {
+ u64 val = (u64)skb->len << TCP_RMEM_TO_WIN_SCALE;
+
+ do_div(val, skb->truesize);
+ tcp_sk(sk)->scaling_ratio = val ? val : 1;
+ }
icsk->icsk_ack.rcv_mss = min_t(unsigned int, len,
tcp_sk(sk)->advmss);
/* Account for possibly-removed options */
@@ -727,8 +737,8 @@ void tcp_rcv_space_adjust(struct sock *sk)
if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_moderate_rcvbuf) &&
!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) {
- int rcvmem, rcvbuf;
u64 rcvwin, grow;
+ int rcvbuf;
/* minimal window to cope with packet losses, assuming
* steady state. Add some cushion because of small variations.
@@ -740,12 +750,7 @@ void tcp_rcv_space_adjust(struct sock *sk)
do_div(grow, tp->rcvq_space.space);
rcvwin += (grow << 1);
- rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
- while (tcp_win_from_space(sk, rcvmem) < tp->advmss)
- rcvmem += 128;
-
- do_div(rcvwin, tp->advmss);
- rcvbuf = min_t(u64, rcvwin * rcvmem,
+ rcvbuf = min_t(u64, tcp_space_from_win(sk, rcvwin),
READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2]));
if (rcvbuf > sk->sk_rcvbuf) {
WRITE_ONCE(sk->sk_rcvbuf, rcvbuf);