* [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option
@ 2024-04-03 22:58 Jon Maloy
2024-04-03 22:58 ` [net-next 1/2] " Jon Maloy
2024-04-03 22:58 ` [net-next 2/2] tcp: correct handling of extreme menory squeeze Jon Maloy
0 siblings, 2 replies; 7+ messages in thread
From: Jon Maloy @ 2024-04-03 22:58 UTC (permalink / raw)
To: passt-dev, sbrivio, lvivier, dgibson, jmaloy
We add support for the SO_PEEK_OFF socket option as a new feature in
TCP.
In a separate patch, we fix a bug that was revealed while testing this
feature.
Jon Maloy (2):
tcp: add support for SO_PEEK_OFF
tcp: correct handling of extreme menory squeeze
net/ipv4/af_inet.c | 1 +
net/ipv4/tcp.c | 16 ++++++++++------
net/ipv4/tcp_output.c | 5 ++++-
3 files changed, 15 insertions(+), 7 deletions(-)
--
2.42.0
^ permalink raw reply [flat|nested] 7+ messages in thread
* [net-next 1/2] tcp: add support for SO_PEEK_OFF socket option
2024-04-03 22:58 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option Jon Maloy
@ 2024-04-03 22:58 ` Jon Maloy
2024-04-03 22:58 ` [net-next 2/2] tcp: correct handling of extreme menory squeeze Jon Maloy
1 sibling, 0 replies; 7+ messages in thread
From: Jon Maloy @ 2024-04-03 22:58 UTC (permalink / raw)
To: passt-dev, sbrivio, lvivier, dgibson, jmaloy
When reading received messages from a socket with MSG_PEEK, we may want
to read the contents with an offset, like we can do with pread/preadv()
when reading files. Currently, it is not possible to do that.
In this commit, we add support for the SO_PEEK_OFF socket option for TCP,
in a similar way it is done for Unix Domain sockets.
In the iperf3 log examples shown below, we can observe a throughput
improvement of 15-20 % in the direction host->namespace when using the
protocol splicer 'pasta' (https://passt.top).
This is a consistent result.
pasta(1) and passt(1) implement user-mode networking for network
namespaces (containers) and virtual machines by means of a translation
layer between Layer-2 network interface and native Layer-4 sockets
(TCP, UDP, ICMP/ICMPv6 echo).
Received, pending TCP data to the container/guest is kept in kernel
buffers until acknowledged, so the tool routinely needs to fetch new
data from socket, skipping data that was already sent.
At the moment this is implemented using a dummy buffer passed to
recvmsg(). With this change, we don't need a dummy buffer and the
related buffer copy (copy_to_user()) anymore.
passt and pasta are supported in KubeVirt and libvirt/qemu.
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF not supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 44822
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 44832
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.02 GBytes 8.78 Gbits/sec
[ 5] 1.00-2.00 sec 1.06 GBytes 9.08 Gbits/sec
[ 5] 2.00-3.00 sec 1.07 GBytes 9.15 Gbits/sec
[ 5] 3.00-4.00 sec 1.10 GBytes 9.46 Gbits/sec
[ 5] 4.00-5.00 sec 1.03 GBytes 8.85 Gbits/sec
[ 5] 5.00-6.00 sec 1.10 GBytes 9.44 Gbits/sec
[ 5] 6.00-7.00 sec 1.11 GBytes 9.56 Gbits/sec
[ 5] 7.00-8.00 sec 1.07 GBytes 9.20 Gbits/sec
[ 5] 8.00-9.00 sec 667 MBytes 5.59 Gbits/sec
[ 5] 9.00-10.00 sec 1.03 GBytes 8.83 Gbits/sec
[ 5] 10.00-10.04 sec 30.1 MBytes 6.36 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 10.3 GBytes 8.78 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
jmaloy@freyr:~/passt#
logout
[ perf record: Woken up 23 times to write data ]
[ perf record: Captured and wrote 5.696 MB perf.data (35580 samples) ]
jmaloy@freyr:~/passt$
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 52084
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 52098
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.32 GBytes 11.3 Gbits/sec
[ 5] 1.00-2.00 sec 1.19 GBytes 10.2 Gbits/sec
[ 5] 2.00-3.00 sec 1.26 GBytes 10.8 Gbits/sec
[ 5] 3.00-4.00 sec 1.36 GBytes 11.7 Gbits/sec
[ 5] 4.00-5.00 sec 1.33 GBytes 11.4 Gbits/sec
[ 5] 5.00-6.00 sec 1.21 GBytes 10.4 Gbits/sec
[ 5] 6.00-7.00 sec 1.31 GBytes 11.2 Gbits/sec
[ 5] 7.00-8.00 sec 1.25 GBytes 10.7 Gbits/sec
[ 5] 8.00-9.00 sec 1.33 GBytes 11.5 Gbits/sec
[ 5] 9.00-10.00 sec 1.24 GBytes 10.7 Gbits/sec
[ 5] 10.00-10.04 sec 56.0 MBytes 12.1 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 12.9 GBytes 11.0 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
logout
[ perf record: Woken up 20 times to write data ]
[ perf record: Captured and wrote 5.040 MB perf.data (33411 samples) ]
jmaloy@freyr:~/passt$
The perf record confirms this result. Below, we can observe that the
CPU spends significantly less time in the function ____sys_recvmsg()
when we have offset support.
Without offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
46.32% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
With offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
28.12% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
v3: - Applied changes suggested by Stefano Brivio and Paolo Abeni
v4: - Same as v3. Posting was delayed because I first had to debug
an issue that turned out to not be directly related to this
change. See next commit in this series.
---
net/ipv4/af_inet.c | 1 +
net/ipv4/tcp.c | 16 ++++++++++------
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index ad278009e469..5c35917b166c 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1071,6 +1071,7 @@ const struct proto_ops inet_stream_ops = {
#endif
.splice_eof = inet_splice_eof,
.splice_read = tcp_splice_read,
+ .set_peek_off = sk_set_peek_off,
.read_sock = tcp_read_sock,
.read_skb = tcp_read_skb,
.sendmsg_locked = tcp_sendmsg_locked,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c82dc42f57c6..d4890f2a86d4 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1415,8 +1415,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2327,6 +2325,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2360,7 +2359,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2463,11 +2463,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2508,7 +2508,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3007,6 +3010,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
@@ -1415,8 +1415,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2327,6 +2325,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2360,7 +2359,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2463,11 +2463,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2508,7 +2508,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3007,6 +3010,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
2.42.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [net-next 2/2] tcp: correct handling of extreme menory squeeze
2024-04-03 22:58 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option Jon Maloy
2024-04-03 22:58 ` [net-next 1/2] " Jon Maloy
@ 2024-04-03 22:58 ` Jon Maloy
2024-04-05 17:55 ` Stefano Brivio
1 sibling, 1 reply; 7+ messages in thread
From: Jon Maloy @ 2024-04-03 22:58 UTC (permalink / raw)
To: passt-dev, sbrivio, lvivier, dgibson, jmaloy
Testing of the previous commit ("tcp: add support for SO_PEEK_OFF")
in this series along with the pasta protocol splicer revealed a bug in
the way tcp handles window advertising during extreme memory squeeze
situations.
The excerpt of the below logging session shows what is happeing:
[5201<->54494]: ==== Activating log @ tcp_select_window()/268 ====
[5201<->54494]: (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM) --> TRUE
[5201<->54494]: tcp_select_window(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354, returning 0
[5201<->54494]: ADVERTISING WINDOW SIZE 0
[5201<->54494]: __tcp_transmit_skb(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: tcp_recvmsg_locked(->)
[5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
[5201<->54494]: NOT calling tcp_send_ack()
[5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 83
[...]
[5201<->54494]: tcp_recvmsg_locked(->)
[5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
[5201<->54494]: NOT calling tcp_send_ack()
[5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 1
[5201<->54494]: tcp_recvmsg_locked(->)
[5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
[5201<->54494]: NOT calling tcp_send_ack()
[5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: tcp_recvmsg_locked(<-) returning 57036 bytes, window now: 250164, qlen: 0
[5201<->54494]: tcp_recvmsg_locked(->)
[5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: NOT calling tcp_send_ack()
[5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
[5201<->54494]: tcp_recvmsg_locked(<-) returning -11 bytes, window now: 250164, qlen: 0
We can see that although we are adverising a window size of zero,
tp->rcv_wnd is not updated accordingly. This leads to a discrepancy
between this side's and the peer's view of the current window size.
- The peer thinks the window is zero, and stops sending.
- This side ends up in a cycle where it repeatedly caclulates a new
window size it finds too small to advertise.
Hence no messages are received, and no acknowledges are sent, and
the situation remains locked even after the last queued receive buffer
has been consumed.
We fix this by setting tp->rcv_wnd to 0 before we return from the
function tcp_select_window() in this particular case.
Further testing shows that the connection recovers neatly from the
squeeze situation, and traffic can continue indefinitely.
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
net/ipv4/tcp_output.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index e3167ad96567..5803fd402708 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -264,8 +264,11 @@ static u16 tcp_select_window(struct sock *sk)
* are out of memory. The window is temporary, so we don't store
* it on the socket.
*/
- if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM))
+ if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
+ tp->rcv_wnd = 0;
+ tp->rcv_wup = tp->rcv_nxt;
return 0;
+ }
cur_win = tcp_receive_window(tp);
new_win = __tcp_select_window(sk);
--
@@ -264,8 +264,11 @@ static u16 tcp_select_window(struct sock *sk)
* are out of memory. The window is temporary, so we don't store
* it on the socket.
*/
- if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM))
+ if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
+ tp->rcv_wnd = 0;
+ tp->rcv_wup = tp->rcv_nxt;
return 0;
+ }
cur_win = tcp_receive_window(tp);
new_win = __tcp_select_window(sk);
--
2.42.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [net-next 2/2] tcp: correct handling of extreme menory squeeze
2024-04-03 22:58 ` [net-next 2/2] tcp: correct handling of extreme menory squeeze Jon Maloy
@ 2024-04-05 17:55 ` Stefano Brivio
2024-04-05 19:37 ` Jon Maloy
0 siblings, 1 reply; 7+ messages in thread
From: Stefano Brivio @ 2024-04-05 17:55 UTC (permalink / raw)
To: Jon Maloy; +Cc: passt-dev, lvivier, dgibson
On Wed, 3 Apr 2024 18:58:33 -0400
Jon Maloy <jmaloy@redhat.com> wrote:
> Testing of the previous commit ("tcp: add support for SO_PEEK_OFF")
> in this series along with the pasta protocol splicer revealed a bug in
> the way tcp handles window advertising during extreme memory squeeze
> situations.
>
> The excerpt of the below logging session shows what is happeing:
>
> [5201<->54494]: ==== Activating log @ tcp_select_window()/268 ====
> [5201<->54494]: (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM) --> TRUE
> [5201<->54494]: tcp_select_window(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354, returning 0
> [5201<->54494]: ADVERTISING WINDOW SIZE 0
> [5201<->54494]: __tcp_transmit_skb(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>
> [5201<->54494]: tcp_recvmsg_locked(->)
> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
> [5201<->54494]: NOT calling tcp_send_ack()
> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 83
>
> [...]
>
> [5201<->54494]: tcp_recvmsg_locked(->)
> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
> [5201<->54494]: NOT calling tcp_send_ack()
> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 1
>
> [5201<->54494]: tcp_recvmsg_locked(->)
> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
> [5201<->54494]: NOT calling tcp_send_ack()
> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: tcp_recvmsg_locked(<-) returning 57036 bytes, window now: 250164, qlen: 0
>
> [5201<->54494]: tcp_recvmsg_locked(->)
> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: NOT calling tcp_send_ack()
> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
> [5201<->54494]: tcp_recvmsg_locked(<-) returning -11 bytes, window now: 250164, qlen: 0
>
> We can see that although we are adverising a window size of zero,
> tp->rcv_wnd is not updated accordingly. This leads to a discrepancy
> between this side's and the peer's view of the current window size.
> - The peer thinks the window is zero, and stops sending.
> - This side ends up in a cycle where it repeatedly caclulates a new
> window size it finds too small to advertise.
>
> Hence no messages are received, and no acknowledges are sent, and
> the situation remains locked even after the last queued receive buffer
> has been consumed.
>
> We fix this by setting tp->rcv_wnd to 0 before we return from the
> function tcp_select_window() in this particular case.
> Further testing shows that the connection recovers neatly from the
> squeeze situation, and traffic can continue indefinitely.
>
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
> net/ipv4/tcp_output.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index e3167ad96567..5803fd402708 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -264,8 +264,11 @@ static u16 tcp_select_window(struct sock *sk)
> * are out of memory. The window is temporary, so we don't store
> * it on the socket.
One nit: now that you do store it on the socket, you should probably
change this comment as well.
> */
> - if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM))
> + if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
> + tp->rcv_wnd = 0;
> + tp->rcv_wup = tp->rcv_nxt;
...I'm wondering if you should set 'pred_flags' to 0, as it's done at
the end of the function for other cases where the window is advertised
as zero.
At least according to the comment to tcp_rcv_established() it looks
like it's needed:
* - A zero window was announced from us - zero window probing
* is only handled properly in the slow path.
> return 0;
> + }
>
> cur_win = tcp_receive_window(tp);
> new_win = __tcp_select_window(sk);
The rest, including 1/2, looks good to me.
--
Stefano
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [net-next 2/2] tcp: correct handling of extreme menory squeeze
2024-04-05 17:55 ` Stefano Brivio
@ 2024-04-05 19:37 ` Jon Maloy
0 siblings, 0 replies; 7+ messages in thread
From: Jon Maloy @ 2024-04-05 19:37 UTC (permalink / raw)
To: Stefano Brivio; +Cc: passt-dev, lvivier, dgibson
On 2024-04-05 13:55, Stefano Brivio wrote:
> On Wed, 3 Apr 2024 18:58:33 -0400
> Jon Maloy <jmaloy@redhat.com> wrote:
>
>> Testing of the previous commit ("tcp: add support for SO_PEEK_OFF")
>> in this series along with the pasta protocol splicer revealed a bug in
>> the way tcp handles window advertising during extreme memory squeeze
>> situations.
>>
>> The excerpt of the below logging session shows what is happeing:
>>
>> [5201<->54494]: ==== Activating log @ tcp_select_window()/268 ====
>> [5201<->54494]: (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM) --> TRUE
>> [5201<->54494]: tcp_select_window(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354, returning 0
>> [5201<->54494]: ADVERTISING WINDOW SIZE 0
>> [5201<->54494]: __tcp_transmit_skb(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>>
>> [5201<->54494]: tcp_recvmsg_locked(->)
>> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
>> [5201<->54494]: NOT calling tcp_send_ack()
>> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 83
>>
>> [...]
>>
>> [5201<->54494]: tcp_recvmsg_locked(->)
>> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
>> [5201<->54494]: NOT calling tcp_send_ack()
>> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: tcp_recvmsg_locked(<-) returning 131072 bytes, window now: 250164, qlen: 1
>>
>> [5201<->54494]: tcp_recvmsg_locked(->)
>> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: (win_now: 250164, new_win: 262144 >= (2 * win_now): 500328))? --> time_to_ack: 0
>> [5201<->54494]: NOT calling tcp_send_ack()
>> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: tcp_recvmsg_locked(<-) returning 57036 bytes, window now: 250164, qlen: 0
>>
>> [5201<->54494]: tcp_recvmsg_locked(->)
>> [5201<->54494]: __tcp_cleanup_rbuf(->) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: NOT calling tcp_send_ack()
>> [5201<->54494]: __tcp_cleanup_rbuf(<-) tp->rcv_wup: 2812454294, tp->rcv_wnd: 5812224, tp->rcv_nxt 2818016354
>> [5201<->54494]: tcp_recvmsg_locked(<-) returning -11 bytes, window now: 250164, qlen: 0
>>
>> We can see that although we are adverising a window size of zero,
>> tp->rcv_wnd is not updated accordingly. This leads to a discrepancy
>> between this side's and the peer's view of the current window size.
>> - The peer thinks the window is zero, and stops sending.
>> - This side ends up in a cycle where it repeatedly caclulates a new
>> window size it finds too small to advertise.
>>
>> Hence no messages are received, and no acknowledges are sent, and
>> the situation remains locked even after the last queued receive buffer
>> has been consumed.
>>
>> We fix this by setting tp->rcv_wnd to 0 before we return from the
>> function tcp_select_window() in this particular case.
>> Further testing shows that the connection recovers neatly from the
>> squeeze situation, and traffic can continue indefinitely.
>>
>> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
>> ---
>> net/ipv4/tcp_output.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
>> index e3167ad96567..5803fd402708 100644
>> --- a/net/ipv4/tcp_output.c
>> +++ b/net/ipv4/tcp_output.c
>> @@ -264,8 +264,11 @@ static u16 tcp_select_window(struct sock *sk)
>> * are out of memory. The window is temporary, so we don't store
>> * it on the socket.
> One nit: now that you do store it on the socket, you should probably
> change this comment as well.
>
>> */
>> - if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM))
>> + if (unlikely(inet_csk(sk)->icsk_ack.pending & ICSK_ACK_NOMEM)) {
>> + tp->rcv_wnd = 0;
>> + tp->rcv_wup = tp->rcv_nxt;
> ...I'm wondering if you should set 'pred_flags' to 0, as it's done at
> the end of the function for other cases where the window is advertised
> as zero.
>
> At least according to the comment to tcp_rcv_established() it looks
> like it's needed:
>
> * - A zero window was announced from us - zero window probing
> * is only handled properly in the slow path.
>
>> return 0;
>> + }
>>
>> cur_win = tcp_receive_window(tp);
>> new_win = __tcp_select_window(sk);
> The rest, including 1/2, looks good to me.
>
Good points. I'll fix those and post the patches with your "Reviewed-by:"
/thx
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [net-next 1/2] tcp: add support for SO_PEEK_OFF socket option
2024-04-06 18:21 ` [net-next 1/2] " jmaloy
@ 2024-04-08 9:46 ` Eric Dumazet
0 siblings, 0 replies; 7+ messages in thread
From: Eric Dumazet @ 2024-04-08 9:46 UTC (permalink / raw)
To: jmaloy
Cc: netdev, davem, kuba, passt-dev, sbrivio, lvivier, dgibson, eric.dumazet
On Sat, Apr 6, 2024 at 8:21 PM <jmaloy@redhat.com> wrote:
>
> From: Jon Maloy <jmaloy@redhat.com>
>
> When reading received messages from a socket with MSG_PEEK, we may want
> to read the contents with an offset, like we can do with pread/preadv()
> when reading files. Currently, it is not possible to do that.
>
> In this commit, we add support for the SO_PEEK_OFF socket option for TCP,
> in a similar way it is done for Unix Domain sockets.
>
> In the iperf3 log examples shown below, we can observe a throughput
> improvement of 15-20 % in the direction host->namespace when using the
> protocol splicer 'pasta' (https://passt.top).
> This is a consistent result.
>
> pasta(1) and passt(1) implement user-mode networking for network
> namespaces (containers) and virtual machines by means of a translation
> layer between Layer-2 network interface and native Layer-4 sockets
> (TCP, UDP, ICMP/ICMPv6 echo).
>
> Received, pending TCP data to the container/guest is kept in kernel
> buffers until acknowledged, so the tool routinely needs to fetch new
> data from socket, skipping data that was already sent.
>
> At the moment this is implemented using a dummy buffer passed to
> recvmsg(). With this change, we don't need a dummy buffer and the
> related buffer copy (copy_to_user()) anymore.
>
> passt and pasta are supported in KubeVirt and libvirt/qemu.
>
> j
> -----------------------------------------------------------
> Server listening on 5201 (test #1)
> -----------------------------------------------------------
> Accepted connection from 192.168.122.1, port 52084
> [ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 52098
> [ ID] Interval Transfer Bitrate
> [ 5] 0.00-1.00 sec 1.32 GBytes 11.3 Gbits/sec
> [ 5] 1.00-2.00 sec 1.19 GBytes 10.2 Gbits/sec
> [ 5] 2.00-3.00 sec 1.26 GBytes 10.8 Gbits/sec
> [ 5] 3.00-4.00 sec 1.36 GBytes 11.7 Gbits/sec
> [ 5] 4.00-5.00 sec 1.33 GBytes 11.4 Gbits/sec
> [ 5] 5.00-6.00 sec 1.21 GBytes 10.4 Gbits/sec
> [ 5] 6.00-7.00 sec 1.31 GBytes 11.2 Gbits/sec
> [ 5] 7.00-8.00 sec 1.25 GBytes 10.7 Gbits/sec
> [ 5] 8.00-9.00 sec 1.33 GBytes 11.5 Gbits/sec
> [ 5] 9.00-10.00 sec 1.24 GBytes 10.7 Gbits/sec
> [ 5] 10.00-10.04 sec 56.0 MBytes 12.1 Gbits/sec
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval Transfer Bitrate
> [ 5] 0.00-10.04 sec 12.9 GBytes 11.0 Gbits/sec receiver
> -----------------------------------------------------------
> Server listening on 5201 (test #2)
> -----------------------------------------------------------
> ^Ciperf3: interrupt - the server has terminated
> logout
> [ perf record: Woken up 20 times to write data ]
> [ perf record: Captured and wrote 5.040 MB perf.data (33411 samples) ]
> jmaloy@freyr:~/passt$
>
> The perf record confirms this result. Below, we can observe that the
> CPU spends significantly less time in the function ____sys_recvmsg()
> when we have offset support.
>
> Without offset support:
> ----------------------
> jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
> -p ____sys_recvmsg -x --stdio -i perf.data | head -1
> 46.32% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
>
> With offset support:
> ----------------------
> jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
> -p ____sys_recvmsg -x --stdio -i perf.data | head -1
> 28.12% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
>
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
>
> ---
> v3: - Applied changes suggested by Stefano Brivio and Paolo Abeni
> v4: - Same as v3. Posting was delayed because I first had to debug
> an issue that turned out to not be directly related to this
> change. See next commit in this series.
This other issue is orthogonal, and might take more time.
SO_RCVLOWAT had a similar issue, please take a look at what we did there.
If you need SO_PEEK_OFF support, I would suggest you submit this patch
as a standalone one.
Reviewed-by: Eric Dumazet <edumazet@google.com>
Thanks.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [net-next 1/2] tcp: add support for SO_PEEK_OFF socket option
2024-04-06 18:21 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option jmaloy
@ 2024-04-06 18:21 ` jmaloy
2024-04-08 9:46 ` Eric Dumazet
0 siblings, 1 reply; 7+ messages in thread
From: jmaloy @ 2024-04-06 18:21 UTC (permalink / raw)
To: netdev, davem
Cc: kuba, passt-dev, jmaloy, sbrivio, lvivier, dgibson, eric.dumazet,
edumazet
From: Jon Maloy <jmaloy@redhat.com>
When reading received messages from a socket with MSG_PEEK, we may want
to read the contents with an offset, like we can do with pread/preadv()
when reading files. Currently, it is not possible to do that.
In this commit, we add support for the SO_PEEK_OFF socket option for TCP,
in a similar way it is done for Unix Domain sockets.
In the iperf3 log examples shown below, we can observe a throughput
improvement of 15-20 % in the direction host->namespace when using the
protocol splicer 'pasta' (https://passt.top).
This is a consistent result.
pasta(1) and passt(1) implement user-mode networking for network
namespaces (containers) and virtual machines by means of a translation
layer between Layer-2 network interface and native Layer-4 sockets
(TCP, UDP, ICMP/ICMPv6 echo).
Received, pending TCP data to the container/guest is kept in kernel
buffers until acknowledged, so the tool routinely needs to fetch new
data from socket, skipping data that was already sent.
At the moment this is implemented using a dummy buffer passed to
recvmsg(). With this change, we don't need a dummy buffer and the
related buffer copy (copy_to_user()) anymore.
passt and pasta are supported in KubeVirt and libvirt/qemu.
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF not supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 44822
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 44832
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.02 GBytes 8.78 Gbits/sec
[ 5] 1.00-2.00 sec 1.06 GBytes 9.08 Gbits/sec
[ 5] 2.00-3.00 sec 1.07 GBytes 9.15 Gbits/sec
[ 5] 3.00-4.00 sec 1.10 GBytes 9.46 Gbits/sec
[ 5] 4.00-5.00 sec 1.03 GBytes 8.85 Gbits/sec
[ 5] 5.00-6.00 sec 1.10 GBytes 9.44 Gbits/sec
[ 5] 6.00-7.00 sec 1.11 GBytes 9.56 Gbits/sec
[ 5] 7.00-8.00 sec 1.07 GBytes 9.20 Gbits/sec
[ 5] 8.00-9.00 sec 667 MBytes 5.59 Gbits/sec
[ 5] 9.00-10.00 sec 1.03 GBytes 8.83 Gbits/sec
[ 5] 10.00-10.04 sec 30.1 MBytes 6.36 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 10.3 GBytes 8.78 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
jmaloy@freyr:~/passt#
logout
[ perf record: Woken up 23 times to write data ]
[ perf record: Captured and wrote 5.696 MB perf.data (35580 samples) ]
jmaloy@freyr:~/passt$
jmaloy@freyr:~/passt$ perf record -g ./pasta --config-net -f
SO_PEEK_OFF supported by kernel.
jmaloy@freyr:~/passt# iperf3 -s
-----------------------------------------------------------
Server listening on 5201 (test #1)
-----------------------------------------------------------
Accepted connection from 192.168.122.1, port 52084
[ 5] local 192.168.122.180 port 5201 connected to 192.168.122.1 port 52098
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 1.32 GBytes 11.3 Gbits/sec
[ 5] 1.00-2.00 sec 1.19 GBytes 10.2 Gbits/sec
[ 5] 2.00-3.00 sec 1.26 GBytes 10.8 Gbits/sec
[ 5] 3.00-4.00 sec 1.36 GBytes 11.7 Gbits/sec
[ 5] 4.00-5.00 sec 1.33 GBytes 11.4 Gbits/sec
[ 5] 5.00-6.00 sec 1.21 GBytes 10.4 Gbits/sec
[ 5] 6.00-7.00 sec 1.31 GBytes 11.2 Gbits/sec
[ 5] 7.00-8.00 sec 1.25 GBytes 10.7 Gbits/sec
[ 5] 8.00-9.00 sec 1.33 GBytes 11.5 Gbits/sec
[ 5] 9.00-10.00 sec 1.24 GBytes 10.7 Gbits/sec
[ 5] 10.00-10.04 sec 56.0 MBytes 12.1 Gbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-10.04 sec 12.9 GBytes 11.0 Gbits/sec receiver
-----------------------------------------------------------
Server listening on 5201 (test #2)
-----------------------------------------------------------
^Ciperf3: interrupt - the server has terminated
logout
[ perf record: Woken up 20 times to write data ]
[ perf record: Captured and wrote 5.040 MB perf.data (33411 samples) ]
jmaloy@freyr:~/passt$
The perf record confirms this result. Below, we can observe that the
CPU spends significantly less time in the function ____sys_recvmsg()
when we have offset support.
Without offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
46.32% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
With offset support:
----------------------
jmaloy@freyr:~/passt$ perf report -q --symbol-filter=do_syscall_64 \
-p ____sys_recvmsg -x --stdio -i perf.data | head -1
28.12% 0.00% passt.avx2 [kernel.vmlinux] [k] do_syscall_64 ____sys_recvmsg
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
v3: - Applied changes suggested by Stefano Brivio and Paolo Abeni
v4: - Same as v3. Posting was delayed because I first had to debug
an issue that turned out to not be directly related to this
change. See next commit in this series.
---
net/ipv4/af_inet.c | 1 +
net/ipv4/tcp.c | 16 ++++++++++------
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 55bd72997b31..a7cfeda28bb2 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1072,6 +1072,7 @@ const struct proto_ops inet_stream_ops = {
#endif
.splice_eof = inet_splice_eof,
.splice_read = tcp_splice_read,
+ .set_peek_off = sk_set_peek_off,
.read_sock = tcp_read_sock,
.read_skb = tcp_read_skb,
.sendmsg_locked = tcp_sendmsg_locked,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 92ee60492314..c0d6fd576d32 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1416,8 +1416,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2328,6 +2326,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2361,7 +2360,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2464,11 +2464,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2509,7 +2509,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3010,6 +3013,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
@@ -1416,8 +1416,6 @@ static int tcp_peek_sndq(struct sock *sk, struct msghdr *msg, int len)
struct sk_buff *skb;
int copied = 0, err = 0;
- /* XXX -- need to support SO_PEEK_OFF */
-
skb_rbtree_walk(skb, &sk->tcp_rtx_queue) {
err = skb_copy_datagram_msg(skb, 0, msg, skb->len);
if (err)
@@ -2328,6 +2326,7 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
int target; /* Read at least this many bytes */
long timeo;
struct sk_buff *skb, *last;
+ u32 peek_offset = 0;
u32 urg_hole = 0;
err = -ENOTCONN;
@@ -2361,7 +2360,8 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
seq = &tp->copied_seq;
if (flags & MSG_PEEK) {
- peek_seq = tp->copied_seq;
+ peek_offset = max(sk_peek_offset(sk, flags), 0);
+ peek_seq = tp->copied_seq + peek_offset;
seq = &peek_seq;
}
@@ -2464,11 +2464,11 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
}
if ((flags & MSG_PEEK) &&
- (peek_seq - copied - urg_hole != tp->copied_seq)) {
+ (peek_seq - peek_offset - copied - urg_hole != tp->copied_seq)) {
net_dbg_ratelimited("TCP(%s:%d): Application bug, race in MSG_PEEK\n",
current->comm,
task_pid_nr(current));
- peek_seq = tp->copied_seq;
+ peek_seq = tp->copied_seq + peek_offset;
}
continue;
@@ -2509,7 +2509,10 @@ static int tcp_recvmsg_locked(struct sock *sk, struct msghdr *msg, size_t len,
WRITE_ONCE(*seq, *seq + used);
copied += used;
len -= used;
-
+ if (flags & MSG_PEEK)
+ sk_peek_offset_fwd(sk, used);
+ else
+ sk_peek_offset_bwd(sk, used);
tcp_rcv_space_adjust(sk);
skip_copy:
@@ -3010,6 +3013,7 @@ int tcp_disconnect(struct sock *sk, int flags)
__skb_queue_purge(&sk->sk_receive_queue);
WRITE_ONCE(tp->copied_seq, tp->rcv_nxt);
WRITE_ONCE(tp->urg_data, 0);
+ sk_set_peek_off(sk, -1);
tcp_write_queue_purge(sk);
tcp_fastopen_active_disable_ofo_check(sk);
skb_rbtree_purge(&tp->out_of_order_queue);
--
2.42.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
end of thread, other threads:[~2024-04-08 9:46 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2024-04-03 22:58 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option Jon Maloy
2024-04-03 22:58 ` [net-next 1/2] " Jon Maloy
2024-04-03 22:58 ` [net-next 2/2] tcp: correct handling of extreme menory squeeze Jon Maloy
2024-04-05 17:55 ` Stefano Brivio
2024-04-05 19:37 ` Jon Maloy
2024-04-06 18:21 [net-next 0/2] tcp: add support for SO_PEEK_OFF socket option jmaloy
2024-04-06 18:21 ` [net-next 1/2] " jmaloy
2024-04-08 9:46 ` Eric Dumazet
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