rxrpc: Fix trace-after-put looking at the put peer record

rxrpc_put_peer() calls trace_rxrpc_peer() after it has done the decrement
of the refcount - which looks at the debug_id in the p

rxrpc: Fix trace-after-put looking at the put peer record

rxrpc_put_peer() calls trace_rxrpc_peer() after it has done the decrement
of the refcount - which looks at the debug_id in the peer record. But
unless the refcount was reduced to zero, we no longer have the right to
look in the record and, indeed, it may be deleted by some other thread.

Fix this by getting the debug_id out before decrementing the refcount and
then passing that into the tracepoint.

This can cause the following symptoms:

BUG: KASAN: use-after-free in __rxrpc_put_peer net/rxrpc/peer_object.c:411
[inline]
BUG: KASAN: use-after-free in rxrpc_put_peer+0x685/0x6a0
net/rxrpc/peer_object.c:435
Read of size 8 at addr ffff888097ec0058 by task syz-executor823/24216

Fixes: 1159d4b496f5 ("rxrpc: Add a tracepoint to track rxrpc_peer refcounting")
Reported-by: syzbot+b9be979c55f2bea8ed30@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Fix rxrpc_recvmsg tracepoint

Fix the rxrpc_recvmsg tracepoint to handle being called with a NULL call
parameter.

Fixes: a25e21f0bcd2 ("rxrpc, afs: Use debug_ids rather th

rxrpc: Fix rxrpc_recvmsg tracepoint

Fix the rxrpc_recvmsg tracepoint to handle being called with a NULL call
parameter.

Fixes: a25e21f0bcd2 ("rxrpc, afs: Use debug_ids rather than pointers in traces")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

rxrpc: Use skb_unshare() rather than skb_cow_data()

The in-place decryption routines in AF_RXRPC's rxkad security module
currently call skb_cow_data() to make sure the data isn't shared

rxrpc: Use skb_unshare() rather than skb_cow_data()

The in-place decryption routines in AF_RXRPC's rxkad security module
currently call skb_cow_data() to make sure the data isn't shared and that
the skb can be written over. This has a problem, however, as the softirq
handler may be still holding a ref or the Rx ring may be holding multiple
refs when skb_cow_data() is called in rxkad_verify_packet() - and so
skb_shared() returns true and __pskb_pull_tail() dislikes that. If this
occurs, something like the following report will be generated.

kernel BUG at net/core/skbuff.c:1463!
...
RIP: 0010:pskb_expand_head+0x253/0x2b0
...
Call Trace:
__pskb_pull_tail+0x49/0x460
skb_cow_data+0x6f/0x300
rxkad_verify_packet+0x18b/0xb10 [rxrpc]
rxrpc_recvmsg_data.isra.11+0x4a8/0xa10 [rxrpc]
rxrpc_kernel_recv_data+0x126/0x240 [rxrpc]
afs_extract_data+0x51/0x2d0 [kafs]
afs_deliver_fs_fetch_data+0x188/0x400 [kafs]
afs_deliver_to_call+0xac/0x430 [kafs]
afs_wait_for_call_to_complete+0x22f/0x3d0 [kafs]
afs_make_call+0x282/0x3f0 [kafs]
afs_fs_fetch_data+0x164/0x300 [kafs]
afs_fetch_data+0x54/0x130 [kafs]
afs_readpages+0x20d/0x340 [kafs]
read_pages+0x66/0x180
__do_page_cache_readahead+0x188/0x1a0
ondemand_readahead+0x17d/0x2e0
generic_file_read_iter+0x740/0xc10
__vfs_read+0x145/0x1a0
vfs_read+0x8c/0x140
ksys_read+0x4a/0xb0
do_syscall_64+0x43/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fix this by using skb_unshare() instead in the input path for DATA packets
that have a security index != 0. Non-DATA packets don't need in-place
encryption and neither do unencrypted DATA packets.

Fixes: 248f219cb8bc ("rxrpc: Rewrite the data and ack handling code")
Reported-by: Julian Wollrath <jwollrath@web.de>
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Use the tx-phase skb flag to simplify tracing

Use the previously-added transmit-phase skbuff private flag to simplify the
socket buffer tracing a bit. Which phase the skbuff come

rxrpc: Use the tx-phase skb flag to simplify tracing

Use the previously-added transmit-phase skbuff private flag to simplify the
socket buffer tracing a bit. Which phase the skbuff comes from can now be
divined from the skb rather than having to be guessed from the call state.

We can also reduce the number of rxrpc_skb_trace values by eliminating the
difference between Tx and Rx in the symbols.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Fix read-after-free in rxrpc_queue_local()

rxrpc_queue_local() attempts to queue the local endpoint it is given and
then, if successful, prints a trace line. The trace line inclu

rxrpc: Fix read-after-free in rxrpc_queue_local()

rxrpc_queue_local() attempts to queue the local endpoint it is given and
then, if successful, prints a trace line. The trace line includes the
current usage count - but we're not allowed to look at the local endpoint
at this point as we passed our ref on it to the workqueue.

Fix this by reading the usage count before queuing the work item.

Also fix the reading of local->debug_id for trace lines, which must be done
with the same consideration as reading the usage count.

Fixes: 09d2bf595db4 ("rxrpc: Add a tracepoint to track rxrpc_local refcounting")
Reported-by: syzbot+78e71c5bab4f76a6a719@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Fix oops in tracepoint

If the rxrpc_eproto tracepoint is enabled, an oops will be cause by the
trace line that rxrpc_extract_header() tries to emit when a protocol error
occur

rxrpc: Fix oops in tracepoint

If the rxrpc_eproto tracepoint is enabled, an oops will be cause by the
trace line that rxrpc_extract_header() tries to emit when a protocol error
occurs (typically because the packet is short) because the call argument is
NULL.

Fix this by using ?: to assume 0 as the debug_id if call is NULL.

This can then be induced by:

echo -e '\0\0\0\0\0\0\0\0' | ncat -4u --send-only <addr> 20001

where addr has the following program running on it:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/rxrpc.h>
int main(void)
{
struct sockaddr_rxrpc srx;
int fd;
memset(&srx, 0, sizeof(srx));
srx.srx_family = AF_RXRPC;
srx.srx_service = 0;
srx.transport_type = AF_INET;
srx.transport_len = sizeof(srx.transport.sin);
srx.transport.sin.sin_family = AF_INET;
srx.transport.sin.sin_port = htons(0x4e21);
fd = socket(AF_RXRPC, SOCK_DGRAM, AF_INET6);
bind(fd, (struct sockaddr *)&srx, sizeof(srx));
sleep(20);
return 0;
}

It results in the following oops.

BUG: kernel NULL pointer dereference, address: 0000000000000340
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
...
RIP: 0010:trace_event_raw_event_rxrpc_rx_eproto+0x47/0xac
...
Call Trace:
<IRQ>
rxrpc_extract_header+0x86/0x171
? rcu_read_lock_sched_held+0x5d/0x63
? rxrpc_new_skb+0xd4/0x109
rxrpc_input_packet+0xef/0x14fc
? rxrpc_input_data+0x986/0x986
udp_queue_rcv_one_skb+0xbf/0x3d0
udp_unicast_rcv_skb.isra.8+0x64/0x71
ip_protocol_deliver_rcu+0xe4/0x1b4
ip_local_deliver+0xf0/0x154
__netif_receive_skb_one_core+0x50/0x6c
netif_receive_skb_internal+0x26b/0x2e9
napi_gro_receive+0xf8/0x1da
rtl8169_poll+0x303/0x4c4
net_rx_action+0x10e/0x333
__do_softirq+0x1a5/0x38f
irq_exit+0x54/0xc4
do_IRQ+0xda/0xf8
common_interrupt+0xf/0xf
</IRQ>
...
? cpuidle_enter_state+0x23c/0x34d
cpuidle_enter+0x2a/0x36
do_idle+0x163/0x1ea
cpu_startup_entry+0x1d/0x1f
start_secondary+0x157/0x172
secondary_startup_64+0xa4/0xb0

Fixes: a25e21f0bcd2 ("rxrpc, afs: Use debug_ids rather than pointers in traces")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it un

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public licence as published by
the free software foundation either version 2 of the licence or at
your option any later version

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 114 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170857.552531963@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

rxrpc: Fix client call connect/disconnect race

rxrpc_disconnect_client_call() reads the call's connection ID protocol
value (call->cid) as part of that function's variable declarations.

rxrpc: Fix client call connect/disconnect race

rxrpc_disconnect_client_call() reads the call's connection ID protocol
value (call->cid) as part of that function's variable declarations. This
is bad because it's not inside the locked section and so may race with
someone granting use of the channel to the call.

This manifests as an assertion failure (see below) where the call in the
presumed channel (0 because call->cid wasn't set when we read it) doesn't
match the call attached to the channel we were actually granted (if 1, 2 or
3).

Fix this by moving the read and dependent calculations inside of the
channel_lock section. Also, only set the channel number and pointer
variables if cid is not zero (ie. unset).

This problem can be induced by injecting an occasional error in
rxrpc_wait_for_channel() before the call to schedule().

Make two further changes also:

(1) Add a trace for wait failure in rxrpc_connect_call().

(2) Drop channel_lock before BUG'ing in the case of the assertion failure.

The failure causes a trace akin to the following:

rxrpc: Assertion failed - 18446612685268945920(0xffff8880beab8c00) == 18446612685268621312(0xffff8880bea69800) is false
------------[ cut here ]------------
kernel BUG at net/rxrpc/conn_client.c:824!
...
RIP: 0010:rxrpc_disconnect_client_call+0x2bf/0x99d
...
Call Trace:
rxrpc_connect_call+0x902/0x9b3
? wake_up_q+0x54/0x54
rxrpc_new_client_call+0x3a0/0x751
? rxrpc_kernel_begin_call+0x141/0x1bc
? afs_alloc_call+0x1b5/0x1b5
rxrpc_kernel_begin_call+0x141/0x1bc
afs_make_call+0x20c/0x525
? afs_alloc_call+0x1b5/0x1b5
? __lock_is_held+0x40/0x71
? lockdep_init_map+0xaf/0x193
? lockdep_init_map+0xaf/0x193
? __lock_is_held+0x40/0x71
? yfs_fs_fetch_data+0x33b/0x34a
yfs_fs_fetch_data+0x33b/0x34a
afs_fetch_data+0xdc/0x3b7
afs_read_dir+0x52d/0x97f
afs_dir_iterate+0xa0/0x661
? iterate_dir+0x63/0x141
iterate_dir+0xa2/0x141
ksys_getdents64+0x9f/0x11b
? filldir+0x111/0x111
? do_syscall_64+0x3e/0x1a0
__x64_sys_getdents64+0x16/0x19
do_syscall_64+0x7d/0x1a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fixes: 45025bceef17 ("rxrpc: Improve management and caching of client connection objects")
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

rxrpc: Fix life check

The life-checking function, which is used by kAFS to make sure that a call
is still live in the event of a pending signal, only samples the received
packet seri

rxrpc: Fix life check

The life-checking function, which is used by kAFS to make sure that a call
is still live in the event of a pending signal, only samples the received
packet serial number counter; it doesn't actually provoke a change in the
counter, rather relying on the server to happen to give us a packet in the
time window.

Fix this by adding a function to force a ping to be transmitted.

kAFS then keeps track of whether there's been a stall, and if so, uses the
new function to ping the server, resetting the timeout to allow the reply
to come back.

If there's a stall, a ping and the call is *still* stalled in the same
place after another period, then the call will be aborted.

Fixes: bc5e3a546d55 ("rxrpc: Use MSG_WAITALL to tell sendmsg() to temporarily ignore signals")
Fixes: f4d15fb6f99a ("rxrpc: Provide functions for allowing cleaner handling of signals")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

rxrpc: Fix the rxrpc_tx_packet trace line

Fix the rxrpc_tx_packet trace line by storing the where parameter.

Fixes: 4764c0da69dc ("rxrpc: Trace packet transmission")
Signed-off-

rxrpc: Fix the rxrpc_tx_packet trace line

Fix the rxrpc_tx_packet trace line by storing the where parameter.

Fixes: 4764c0da69dc ("rxrpc: Trace packet transmission")
Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Fix error distribution

Fix error distribution by immediately delivering the errors to all the
affected calls rather than deferring them to a worker thread. The problem
with t

rxrpc: Fix error distribution

Fix error distribution by immediately delivering the errors to all the
affected calls rather than deferring them to a worker thread. The problem
with the latter is that retries and things can happen in the meantime when we
want to stop that sooner.

To this end:

(1) Stop the error distributor from removing calls from the error_targets
list so that peer->lock isn't needed to synchronise against other adds
and removals.

(2) Require the peer's error_targets list to be accessed with RCU, thereby
avoiding the need to take peer->lock over distribution.

(3) Don't attempt to affect a call's state if it is already marked complete.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Trace socket notification

Trace notifications from the softirq side of the socket to the
process-context side.

Signed-off-by: David Howells <dhowells@redhat.com>

rxrpc: Fix ACK proposal tracepoint

Fix the ACK proposal tracepoint outcomes list by making the one that's an
empty string not an empty string - which gets rendered as a hex number
st

rxrpc: Fix ACK proposal tracepoint

Fix the ACK proposal tracepoint outcomes list by making the one that's an
empty string not an empty string - which gets rendered as a hex number
string instead.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Trace packet transmission

Trace successful packet transmission (kernel_sendmsg() succeeded, that is)
in AF_RXRPC. We can share the enum that defines the transmission points
w

rxrpc: Trace packet transmission

Trace successful packet transmission (kernel_sendmsg() succeeded, that is)
in AF_RXRPC. We can share the enum that defines the transmission points
with the trace_rxrpc_tx_fail() tracepoint, so rename its constants to be
applicable to both.

Also, save the internal call->debug_id in the rxrpc_channel struct so that
it can be used in retransmission trace lines.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Fix handling of call quietly cancelled out on server

Sometimes an in-progress call will stop responding on the fileserver when
the fileserver quietly cancels the call with an inte

rxrpc: Fix handling of call quietly cancelled out on server

Sometimes an in-progress call will stop responding on the fileserver when
the fileserver quietly cancels the call with an internally marked abort
(RX_CALL_DEAD), without sending an ABORT to the client.

This causes the client's call to eventually expire from lack of incoming
packets directed its way, which currently leads to it being cancelled
locally with ETIME. Note that it's not currently clear as to why this
happens as it's really hard to reproduce.

The rotation policy implement by kAFS, however, doesn't differentiate
between ETIME meaning we didn't get any response from the server and ETIME
meaning the call got cancelled mid-flow. The latter leads to an oops when
fetching data as the rotation partially resets the afs_read descriptor,
which can result in a cleared page pointer being dereferenced because that
page has already been filled.

Handle this by the following means:

(1) Set a flag on a call when we receive a packet for it.

(2) Store the highest packet serial number so far received for a call
(bearing in mind this may wrap).

(3) If, when the "not received anything recently" timeout expires on a
call, we've received at least one packet for a call and the connection
as a whole has received packets more recently than that call, then
cancel the call locally with ECONNRESET rather than ETIME.

This indicates that the call was definitely in progress on the server.

(4) In kAFS, if the rotation algorithm sees ECONNRESET rather than ETIME,
don't try the next server, but rather abort the call.

This avoids the oops as we don't try to reuse the afs_read struct.
Rather, as-yet ungotten pages will be reread at a later data.

Also:

(5) Add an rxrpc tracepoint to log detection of the call being reset.

Without this, I occasionally see an oops like the following:

general protection fault: 0000 [#1] SMP PTI
...
RIP: 0010:_copy_to_iter+0x204/0x310
RSP: 0018:ffff8800cae0f828 EFLAGS: 00010206
RAX: 0000000000000560 RBX: 0000000000000560 RCX: 0000000000000560
RDX: ffff8800cae0f968 RSI: ffff8800d58b3312 RDI: 0005080000000000
RBP: ffff8800cae0f968 R08: 0000000000000560 R09: ffff8800ca00f400
R10: ffff8800c36f28d4 R11: 00000000000008c4 R12: ffff8800cae0f958
R13: 0000000000000560 R14: ffff8800d58b3312 R15: 0000000000000560
FS: 00007fdaef108080(0000) GS:ffff8800ca680000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb28a8fa000 CR3: 00000000d2a76002 CR4: 00000000001606e0
Call Trace:
skb_copy_datagram_iter+0x14e/0x289
rxrpc_recvmsg_data.isra.0+0x6f3/0xf68
? trace_buffer_unlock_commit_regs+0x4f/0x89
rxrpc_kernel_recv_data+0x149/0x421
afs_extract_data+0x1e0/0x798
? afs_wait_for_call_to_complete+0xc9/0x52e
afs_deliver_fs_fetch_data+0x33a/0x5ab
afs_deliver_to_call+0x1ee/0x5e0
? afs_wait_for_call_to_complete+0xc9/0x52e
afs_wait_for_call_to_complete+0x12b/0x52e
? wake_up_q+0x54/0x54
afs_make_call+0x287/0x462
? afs_fs_fetch_data+0x3e6/0x3ed
? rcu_read_lock_sched_held+0x5d/0x63
afs_fs_fetch_data+0x3e6/0x3ed
afs_fetch_data+0xbb/0x14a
afs_readpages+0x317/0x40d
__do_page_cache_readahead+0x203/0x2ba
? ondemand_readahead+0x3a7/0x3c1
ondemand_readahead+0x3a7/0x3c1
generic_file_buffered_read+0x18b/0x62f
__vfs_read+0xdb/0xfe
vfs_read+0xb2/0x137
ksys_read+0x50/0x8c
do_syscall_64+0x7d/0x1a0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Note the weird value in RDI which is a result of trying to kmap() a NULL
page pointer.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

show more ...

rxrpc: Trace UDP transmission failure

Add a tracepoint to log transmission failure from the UDP transport socket
being used by AF_RXRPC.

Signed-off-by: David Howells <dhowells@r

rxrpc: Trace UDP transmission failure

Add a tracepoint to log transmission failure from the UDP transport socket
being used by AF_RXRPC.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Add a tracepoint to log ICMP/ICMP6 and error messages

Add a tracepoint to log received ICMP/ICMP6 events and other error
messages.

Signed-off-by: David Howells <dhowells@

rxrpc: Add a tracepoint to log ICMP/ICMP6 and error messages

Add a tracepoint to log received ICMP/ICMP6 events and other error
messages.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Add a tracepoint to track rxrpc_peer refcounting

Add a tracepoint to track reference counting on the rxrpc_peer struct.

Signed-off-by: David Howells <dhowells@redhat.com>

rxrpc: Add a tracepoint to track rxrpc_local refcounting

Add a tracepoint to track reference counting on the rxrpc_local struct.

Signed-off-by: David Howells <dhowells@redhat.com>

rxrpc: Trace call completion

Add a tracepoint to track rxrpc calls moving into the completed state and
to log the completion type and the recorded error value and abort code.

Si

rxrpc: Trace call completion

Add a tracepoint to track rxrpc calls moving into the completed state and
to log the completion type and the recorded error value and abort code.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc, afs: Use debug_ids rather than pointers in traces

In rxrpc and afs, use the debug_ids that are monotonically allocated to
various objects as they're allocated rather than pointers

rxrpc, afs: Use debug_ids rather than pointers in traces

In rxrpc and afs, use the debug_ids that are monotonically allocated to
various objects as they're allocated rather than pointers as kernel
pointers are now hashed making them less useful. Further, the debug ids
aren't reused anywhere nearly as quickly.

In addition, allow kernel services that use rxrpc, such as afs, to take
numbers from the rxrpc counter, assign them to their own call struct and
pass them in to rxrpc for both client and service calls so that the trace
lines for each will have the same ID tag.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Trace resend

Add a tracepoint to trace packet resend events and to dump the Tx
annotation buffer for added illumination.

Signed-off-by: David Howells <dhowells@rdhat.com>

rxrpc: Fix service endpoint expiry

RxRPC service endpoints expire like they're supposed to by the following
means:

(1) Mark dead rxrpc_net structs (with ->live) rather than twi

rxrpc: Fix service endpoint expiry

RxRPC service endpoints expire like they're supposed to by the following
means:

(1) Mark dead rxrpc_net structs (with ->live) rather than twiddling the
global service conn timeout, otherwise the first rxrpc_net struct to
die will cause connections on all others to expire immediately from
then on.

(2) Mark local service endpoints for which the socket has been closed
(->service_closed) so that the expiration timeout can be much
shortened for service and client connections going through that
endpoint.

(3) rxrpc_put_service_conn() needs to schedule the reaper when the usage
count reaches 1, not 0, as idle conns have a 1 count.

(4) The accumulator for the earliest time we might want to schedule for
should be initialised to jiffies + MAX_JIFFY_OFFSET, not ULONG_MAX as
the comparison functions use signed arithmetic.

(5) Simplify the expiration handling, adding the expiration value to the
idle timestamp each time rather than keeping track of the time in the
past before which the idle timestamp must go to be expired. This is
much easier to read.

(6) Ignore the timeouts if the net namespace is dead.

(7) Restart the service reaper work item rather the client reaper.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Add keepalive for a call

We need to transmit a packet every so often to act as a keepalive for the
peer (which has a timeout from the last time it received a packet) and also

rxrpc: Add keepalive for a call

We need to transmit a packet every so often to act as a keepalive for the
peer (which has a timeout from the last time it received a packet) and also
to prevent any intervening firewalls from closing the route.

Do this by resetting a timer every time we transmit a packet. If the timer
ever expires, we transmit a PING ACK packet and thereby also elicit a PING
RESPONSE ACK from the other side - which prevents our last-rx timeout from
expiring.

The timer is set to 1/6 of the last-rx timeout so that we can detect the
other side going away if it misses 6 replies in a row.

This is particularly necessary for servers where the processing of the
service function may take a significant amount of time.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...

rxrpc: Add a timeout for detecting lost ACKs/lost DATA

Add an extra timeout that is set/updated when we send a DATA packet that
has the request-ack flag set. This allows us to detect if

rxrpc: Add a timeout for detecting lost ACKs/lost DATA

Add an extra timeout that is set/updated when we send a DATA packet that
has the request-ack flag set. This allows us to detect if we don't get an
ACK in response to the latest flagged packet.

The ACK packet is adjudged to have been lost if it doesn't turn up within
2*RTT of the transmission.

If the timeout occurs, we schedule the sending of a PING ACK to find out
the state of the other side. If a new DATA packet is ready to go sooner,
we cancel the sending of the ping and set the request-ack flag on that
instead.

If we get back a PING-RESPONSE ACK that indicates a lower tx_top than what
we had at the time of the ping transmission, we adjudge all the DATA
packets sent between the response tx_top and the ping-time tx_top to have
been lost and retransmit immediately.

Rather than sending a PING ACK, we could just pick a DATA packet and
speculatively retransmit that with request-ack set. It should result in
either a REQUESTED ACK or a DUPLICATE ACK which we can then use in lieu the
a PING-RESPONSE ACK mentioned above.

Signed-off-by: David Howells <dhowells@redhat.com>

show more ...