This bug impacts only the backends.
When entering the closing state, a quic_closed_conn is used to replace the quic_conn.
In this state, the ->fd value was reset to -1 value calling qc_init_fd(). This value
is used by qc_may_use_saddr() which supposes it cannot be -1 for a backend, leading
->li to be dereferencd, which is legal only for a listener.
This bug impacts only the backend but with possible crash when qc_may_use_saddr()
is called: qc_test_fd() is false leading qc->li to be dereferenced. This is legal
only for a listener.
This patch prevents such fd value resettings for backends.
No need to backport because the QUIC backends support arrived with 3.3.
A quic_conn_closed struct is initialized to replace the quic_conn when the
connection enters the closing to reduce the connection memory footprint.
->max_udp_payload quic_conn_close was not initialized leading to possible
BUG_ON()s in qc_rcv_buf() when comparing the RX buf size to this payload.
->cntrs counters were alon not initialized with the only consequence
to generate wrong values for these counters.
Must be backported as far as 2.9.
The ->li (struct listener *) member of quic_conn struct was replaced by a
->target (struct obj_type *) member by this commit:
MINOR: quic-be: get rid of ->li quic_conn member
to abstract the connection type (front or back) when implementing QUIC for the
backends. In these cases, ->target was a pointer to the ojb_type of a server
struct. This could not work with the dynamic servers contrary to the listeners
which are not dynamic.
This patch almost reverts the one mentioned above. ->target pointer to obj_type member
is replaced by ->li pointer to listener struct member. As the listener are not
dynamic, this is easy to do this. All one has to do is to replace the
objt_listener(qc->target) statement by qc->li where applicable.
For the backend connection, when needed, this is always qc->conn->target which is
used only when qc->conn is initialized. The only "problematic" case is for
quic_dgram_parse() which takes a pointer to an obj_type as third argument.
But this obj_type is only used to call quic_rx_pkt_parse(). Inside this function
it is used to access the proxy counters of the connection thanks to qc_counters().
So, this obj_type argument may be null for now on with this patch. This is the
reason why qc_counters() is modified to take this into consideration.
Previously, GSO emission was explicitely disabled on backend side. This
is not true since the following patch, thus GSO can be used, for example
when transfering large POST requests to a HTTP/3 backend.
commit e064e5d46171d32097a84b8f84ccc510a5c211db
MINOR: quic: duplicate GSO unsupp status from listener to conn
However, GSO on the backend side may cause crash when handling EIO. In
this case, GSO must be completely disabled. Previously, this was
performed by flagging listener instance. In backend side, this would
cause a crash as listener is NULL.
This patch fixes it by supporting GSO disable flag for servers. Thus, in
qc_send_ppkts(), EIO can be converted either to a listener or server
flag depending on the quic_conn proxy side. On backend side, server
instance is retrieved via <qc.conn.target>. This is enough to guarantee
that server is not deleted.
This does not need to be backported.
This bug arrived with this fix:
BUG/MINOR: quic-be: missing Initial packet number space discarding
leading to crashes when dereferencing ->ipktns.
Such crashes could be reproduced with -dMfail option. To reach them, the
memory allocations must fail. So, this is relatively rare, except on systems
with limited memory.
To fix this, do not call quic_pktns_discard() if ->ipktns is NULL.
No need to backport.
This bug impacts only the QUIC backends. It arrived with this commit:
MINOR: quic-be: QUIC connection allocation adaptation (qc_new_conn())
which was supposed to be fixed by:
BUG/MEDIUM: quic: crash after quic_conn allocation failures
but this commit was not sufficient.
Such a crashe could be reproduced with -dMfail option. To reach it, the
<conn_id> object allocation must fail (from qc_new_conn()). So, this is
relatively rare, except on systems with limited memory.
No need to backport.
This bug arrived with this commit:
BUG/MEDIUM: quic: do not release BE quic-conn prior to upper conn
which added a BUG_ON(qc->conn) statement at the beginning of quic_conn_release().
It is triggered if the connection is not released before releasing the quic_conn.
But this is always the case for a backend quic_conn when its allocation from
qc_new_conn() fails.
Such crashes could be reproduced with -dMfail option. To reach them, the
memory allocations must fail. So, this is relatively rare, except on systems
with limited memory.
To fix this, simply set ->conn quic_conn struct member to a not null value
(the one passed as parameter) after the quic_conn allocation has succeeded.
No backport needed.
This regression arrived with this commit:
MINOR: quic-be: QUIC connection allocation adaptation (qc_new_conn())
where qc_new_conn() was modified. The ->cids allocation was moved without
checking if a quic_conn_release() call could lead to crashes due to uninitialized
quic_conn members. Indeed, if qc_new_conn() fails, then quic_conn_release() is
called. This bug could impact both QUIC servers and clients.
Such crashes could be reproduced with -dMfail option. To reach them, the
memory allocations must fail. So, this is relatively rare, except on systems
with limited memory.
This patch ensures all the quic_conn members which could lead to crash
from quic_conn_release() are initialized before any remaining memory allocations
required for the quic_conn.
The <conn_id> variable allocated by the client is no more attached to
the connection during its allocation, but after the ->cids trees is allocated.
No backport needed.
This issue was reported in GH #3071 by @famfo where a wireshark capture
reveals that some handshake could not complete after having received
two Initial packets. This could happen when the packets were parsed
in two times, calling qc_ssl_provide_all_quic_data() two times.
This is due to crypto data stream counter which was incremented two times
from qc_ssl_provide_all_quic_data() (see cstream->rx.offset += data
statement around line 1223 in quic_ssl.c). One time by the callback
which "receives" the crypto data, and on time by qc_ssl_provide_all_quic_data().
Then when parsing the second crypto data frame, the parser detected
that the crypto were already provided.
To fix this, one could comment the code which increment the crypto data
stream counter by <data>. That said, when using the OpenSSL 3.5 QUIC API
one should not modified the crypto data stream outside of the OpenSSL 3.5
QUIC API.
So, this patch stop calling qc_ssl_provide_all_quic_data() and
qc_ssl_provide_quic_data() and only calls qc_ssl_do_hanshake() after
having received some crypto data. In addition to this, as these functions
are no more called when building haproxy against OpenSSL 3.5, this patch
disable their compilations (with #ifndef HAVE_OPENSSL_QUIC).
This patch depends on this previous one:
MINOR: quic: implement qc_ssl_do_hanshake()
Thank you to @famto for this report.
Must be backported to 3.2.
This will make the pools size and alignment automatically inherit
the type declaration. It was done like this:
sed -i -e 's:DECLARE_POOL(\([^,]*,[^,]*,\s*\)sizeof(\([^)]*\))):DECLARE_TYPED_POOL(\1\2):g' $(git grep -lw DECLARE_POOL src addons)
sed -i -e 's:DECLARE_STATIC_POOL(\([^,]*,[^,]*,\s*\)sizeof(\([^)]*\))):DECLARE_STATIC_TYPED_POOL(\1\2):g' $(git grep -lw DECLARE_STATIC_POOL src addons)
81 replacements were made. The only remaining ones are those which set
their own size without depending on a structure. The few ones with an
extra size were manually handled.
It also means that the requested alignments are now checked against the
type's. Given that none is specified for now, no issue is reported.
It was verified with "show pools detailed" that the definitions are
exactly the same, and that the binaries are similar.
Previously quic_conn <target> member was used to determine if quic_conn
was used on the frontend (as server) or backend side (as client). A new
helper function can now be used to directly check flag
QUIC_FL_CONN_IS_BACK.
This reduces the dependency between quic_conn and their relative
listener/server instances.
Define a new quic_conn flag assign if the connection is used on the
backend side. This is similar to other haproxy components such as struct
connection and muxes element.
This flag is positionned via qc_new_conn(). Also update quic traces to
mark proxy side as 'F' or 'B' suffix.
QUIC emission can use GSO to emit multiple datagrams with a single
syscall invokation. However, this feature relies on several kernel
parameters which are checked on haproxy process startup.
Even if these checks report no issue, GSO may still be unable due to the
underlying network adapter underneath. Thus, if a EIO occured on
sendmsg() with GSO, listener is flagged to mark GSO as unsupported. This
allows every other QUIC connections to share the status and avoid using
GSO when using this listener.
Previously, listener flag was checked for every QUIC emission. This was
done using an atomic operation to prevent races. Improve this by
duplicating GSO unsupported status as the connection level. This is done
on qc_new_conn() and also on thread rebinding if a new listener instance
is used.
The main benefit from this patch is to reduce the dependency between
quic_conn and listener instances.
This patch impacts the QUIC frontends. It reverts this patch
MINOR: quic-be: add a "CC connection" backend TX buffer pool
which adds <pool_head_quic_be_cc_buf> new pool to allocate CC (connection closed state)
TX buffers with bigger object size than the one for <pool_head_quic_cc_buf>.
Indeed the QUIC backends must be able to send at least 1200 bytes Initial packets.
For now on, both the QUIC frontends and backend use the same pool with
MAX(QUIC_INITIAL_IPV6_MTU, QUIC_INITIAL_IPV4_MTU)(1252 bytes) as object size.
The "connection close state" TX buffer is used to build the datagram with
basically a CONNECTION_CLOSE frame to notify the peer about the connection
closure. It allows the quic_conn memory release and its replacement by a lighter
quic_cc_conn struct.
For the QUIC backend, there is a dedicated pool to build such datagrams from
bigger TX buffers. But from quic_conn_release(), this is the pool dedicated
to the QUIC frontends which was used to release the QUIC backend TX buffers.
This patch simply adds a test about the target of the connection to release
the "connection close state" TX buffers from the correct pool.
No backport needed.
Replace all calls to qc_is_listener() (resp. !qc_is_listener()) by calls to
objt_listener() (resp. objt_server()).
Remove qc_is_listener() implement and QUIC_FL_CONN_LISTENER the flag it
relied on.
- Add ->retry_token and ->retry_token_len new quic_conn struct members to store
the retry tokens. These objects are allocated by quic_rx_packet_parse() and
released by quic_conn_release().
- Add <pool_head_quic_retry_token> new pool for these tokens.
- Implement quic_retry_packet_check() to check the integrity tag of these tokens
upon RETRY packets receipt. quic_tls_generate_retry_integrity_tag() is called
by this new function. It has been modified to pass the address where the tag
must be generated
- Add <resend> new parameter to quic_pktns_discard(). This function is called
to discard the packet number spaces where the already TX packets and frames are
attached to. <resend> allows the caller to prevent this function to release
the in flight TX packets/frames. The frames are requeued to be resent.
- Modify quic_rx_pkt_parse() to handle the RETRY packets. What must be done upon
such packets receipt is:
- store the retry token,
- store the new peer SCID as the DCID of the connection. Note that the peer will
modify again its SCID. This is why this SCID is also stored as the ODCID
which must be matched with the peer retry_source_connection_id transport parameter,
- discard the Initial packet number space without flagging it as discarded and
prevent retransmissions calling qc_set_timer(),
- modify the TLS cryptographic cipher contexts (RX/TX),
- wakeup the I/O handler to send new Initial packets asap.
- Modify quic_transport_param_decode() to handle the retry_source_connection_id
transport parameter as a QUIC client. Then its caller is modified to
check this transport parameter matches with the SCID sent by the peer with
the RETRY packet.
A QUIC client must be able to close a connection sending Initial packets. But
QUIC client Initial packets must always be at least 1200 bytes long. To reduce
the memory use of TX buffers of a connection when in "closing" state, a pool
was dedicated for this purpose but with a too much reduced TX buffer size
(QUIC_MAX_CC_BUFSIZE).
This patch adds a "closing state connection" TX buffer pool with the same role
for QUIC backends.
For frontend side, quic_conn is only released if MUX wasn't allocated,
either due to handshake abort, in which case upper layer is never
allocated, or after transfer completion when full conn + MUX layers are
already released.
On the backend side, initialization is not performed in the same order.
Indeed, in this case, connection is first instantiated, the nthe
quic_conn is created to execute the handshake, while MUX is still only
allocated on handshake completion. As such, it is not possible anymore
to free immediately quic_conn on handshake failure. Else, this can cause
crash if the connection try to reaccess to its transport layer after
quic_conn release.
Such crash can easily be reproduced in case of connection error to the
QUIC server. Here is an example of an experienced backtrace.
Thread 1 "haproxy" received signal SIGSEGV, Segmentation fault.
0x0000555555739733 in quic_close (conn=0x55555734c0d0, xprt_ctx=0x5555573a6e50) at src/xprt_quic.c:28
28 qc->conn = NULL;
[ ## gdb ## ] bt
#0 0x0000555555739733 in quic_close (conn=0x55555734c0d0, xprt_ctx=0x5555573a6e50) at src/xprt_quic.c:28
#1 0x00005555559c9708 in conn_xprt_close (conn=0x55555734c0d0) at include/haproxy/connection.h:162
#2 0x00005555559c97d2 in conn_full_close (conn=0x55555734c0d0) at include/haproxy/connection.h:206
#3 0x00005555559d01a9 in sc_detach_endp (scp=0x7fffffffd648) at src/stconn.c:451
#4 0x00005555559d05b9 in sc_reset_endp (sc=0x55555734bf00) at src/stconn.c:533
#5 0x000055555598281d in back_handle_st_cer (s=0x55555734adb0) at src/backend.c:2754
#6 0x000055555588158a in process_stream (t=0x55555734be10, context=0x55555734adb0, state=516) at src/stream.c:1907
#7 0x0000555555dc31d9 in run_tasks_from_lists (budgets=0x7fffffffdb30) at src/task.c:655
#8 0x0000555555dc3dd3 in process_runnable_tasks () at src/task.c:889
#9 0x0000555555a1daae in run_poll_loop () at src/haproxy.c:2865
#10 0x0000555555a1e20c in run_thread_poll_loop (data=0x5555569d1c00 <ha_thread_info>) at src/haproxy.c:3081
#11 0x0000555555a1f66b in main (argc=5, argv=0x7fffffffde18) at src/haproxy.c:3671
To fix this, change the condition prior to calling quic_conn release. If
<conn> member is not NULL, delay the release, similarly to the case when
MUX is allocated. This allows connection to be freed first, and detach
from quic_conn layer through close xprt operation.
No need to backport.
QUIC support on the backend side has been implemented recently. This has
lead to some adjustment on qc_new_conn() to handle both FE and BE sides,
with some of these changes performed by the following commit.
29fb1aee57288a8b16ed91771ae65c2bfa400128
MINOR: quic-be: QUIC connection allocation adaptation (qc_new_conn())
An issue was introduced during some code adjustement. Initialization of
ODCID was incorrectly performed, which caused haproxy to emit invalid
transport parameters. Most of the clients detected this and immediatly
closed the connection.
Fix this by adjusting qc_lstnr_params_init() invokation : replace
<qc.dcid>, which in fact points to the received SCID, by <qc.odcid>
whose purpose is dedicated to original DCID storage.
This fixes github issue #3006. This issue also caused the majority of
tests in the interop to fail.
No backport needed.
This issue may occur when qc_new_conn() fails after having allocated
and attached <conn_cid> to its tree. This is the case when compiling
haproxy against WolfSSL for an unknown reason at this time. In this
case the <conn_cid> is freed by pool_head_quic_connection_id(), then
freed again by quic_conn_release().
This bug arrived with this commit:
MINOR: quic-be: QUIC connection allocation adaptation (qc_new_conn())
So, the aim of this patch is to free <conn_cid> only for QUIC backends
and if it is not attached to its tree. This is the case when <conn_id>
local variable passed with NULL value to qc_new_conn() is then intialized
to the same <conn_cid> value.
This patch should have come with this last commit for the last qc_new_conn()
modifications for QUIC backends:
MINOR: quic-be: get rid of ->li quic_conn member
qc_new_conn() must be passed NULL pointers for several variables as mentioned
by the comment. Some of these local variables are used to avoid too much
code modifications.
Replace ->li quic_conn pointer to struct listener member by ->target which is
an object type enum and adapt the code.
Use __objt_(listener|server)() where the object type is known. Typically
this is were the code which is specific to one connection type (frontend/backend).
Remove <server> parameter passed to qc_new_conn(). It is redundant with the
<target> parameter.
GSO is not supported at this time for QUIC backend. qc_prep_pkts() is modified
to prevent it from building more than an MTU. This has as consequence to prevent
qc_send_ppkts() to use GSO.
ssl_clienthello.c code is run only by listeners. This is why __objt_listener()
is used in place of ->li.
For connection to QUIC servers, this patch modifies the moment where the I/O
handler callback is switched to quic_conn_app_io_cb(). This is no more
done as for listener just after the handshake has completed but just after
it has been confirmed.
Discard the Initial packet number space as soon as possible. This is done
during handshakes in quic_conn_io_cb() as soon as an Handshake packet could
be successfully sent.
Allocate a connection to connect to QUIC servers from qc_conn_init() which is the
->init() QUIC xprt callback.
Also initialize ->prepare_srv and ->destroy_srv callback as this done for TCP
servers.
For haproxy QUIC servers (or QUIC clients), the peer is considered as validated.
This is a property which is more specific to QUIC servers (haproxy QUIC listeners).
No <odcid> is used for the QUIC client connection. It is used only on the QUIC server side.
The <token_odcid> is also not used on the QUIC client side. It must be embedded into
the transport parameters only on the QUIC server side.
The quic_conn is created before the socket allocation. So, the local address is
zeroed.
Initilize the transport parameter with qc_srv_params_init().
Stop hardcoding the <server> parameter passed value to qc_new_isecs() to correctly
initialize the Initial secrets.
Modify qc_alloc_ssl_sock_ctx() to pass the connection object as parameter. It is
NULL for a QUIC listener, not NULL for a QUIC server. This connection object is
set as value for ->conn quic_conn struct member. Initialise the SSL session object from
this function for QUIC servers.
qc_ssl_set_quic_transport_params() is also modified to pass the SSL object as parameter.
This is the unique parameter this function needs. <qc> parameter is used only for
the trace.
SSL_do_handshake() must be calle as soon as the SSL object is initialized for
the QUIC backend connection. This triggers the TLS CRYPTO data delivery.
tasklet_wakeup() is also called to send asap these CRYPTO data.
Modify the QUIC_EV_CONN_NEW event trace to dump the potential errors returned by
SSL_do_handshake().
According to the RFC, a QUIC client must encode the QUIC version it supports
into the "Available Versions" of "Version Information" transport parameter
order by descending preference.
This is done defining <quic_version_2> and <quic_version_draft_29> new variables
pointers to the corresponding version of <quic_versions> array elements.
A client announces its available versions as follows: v1, v2, draft29.
quic-conn layer has to handle itself STREAM frames after MUX release. If
the stream was already seen, it is probably only a retransmitted frame
which can be safely ignored. For other streams, an active closure may be
needed.
Thus it's necessary that quic-conn layer knows the highest stream ID
already handled by the MUX after its release. Previously, this was done
via <nb_streams> member array in quic-conn structure.
Refactor this by replacing <nb_streams> by two members called
<stream_max_uni>/<stream_max_bidi>. Indeed, it is unnecessary for
quic-conn layer to monitor locally opened uni streams, as the peer
cannot by definition emit a STREAM frame on it. Also, bidirectional
streams are always opened by the remote side.
Previously, <nb_streams> were set by quic-stream layer. Now,
<stream_max_uni>/<stream_max_bidi> members are only set one time, just
prior to QUIC MUX release. This is sufficient as quic-conn do not use
them if the MUX is available.
Note that previously, IDs were used relatively to their type, thus
incremented by 1, after shifting the original value. For simplification,
use the plain stream ID, which is incremented by 4.
Move general function to check if a stream is uni or bidirectional from
QUIC MUX to quic_utils module. This should prevent unnecessary include
of QUIC MUX header file in other sources.
The quic_conn struct is modified for two reasons. The first one is to store
the encoded version of the local tranport parameter as this is done for
USE_QUIC_OPENSSL_COMPAT. Indeed, the local transport parameter "should remain
valid until after the parameters have been sent" as mentionned by
SSL_set_quic_tls_cbs(3) manual. In our case, the buffer is a static buffer
attached to the quic_conn object. qc_ssl_set_quic_transport_params() function
whose role is to call SSL_set_tls_quic_transport_params() (aliased by
SSL_set_quic_transport_params() to set these local tranport parameter into
the TLS stack from the buffer attached to the quic_conn struct.
The second quic_conn struct modification is the addition of the new ->prot_level
(SSL protection level) member added to the quic_conn struct to store "the most
recent write encryption level set via the OSSL_FUNC_SSL_QUIC_TLS_yield_secret_fn
callback (if it has been called)" as mentionned by SSL_set_quic_tls_cbs(3) manual.
This patches finally implements the five remaining callacks to make the haproxy
QUIC implementation work.
OSSL_FUNC_SSL_QUIC_TLS_crypto_send_fn() (ha_quic_ossl_crypto_send) is easy to
implement. It calls ha_quic_add_handshake_data() after having converted
qc->prot_level TLS protection level value to the correct ssl_encryption_level_t
(boringSSL API/quictls) value.
OSSL_FUNC_SSL_QUIC_TLS_crypto_recv_rcd_fn() (ha_quic_ossl_crypto_recv_rcd())
provide the non-contiguous addresses to the TLS stack, without releasing
them.
OSSL_FUNC_SSL_QUIC_TLS_crypto_release_rcd_fn() (ha_quic_ossl_crypto_release_rcd())
release these non-contiguous buffer relying on the fact that the list of
encryption level (qc->qel_list) is correctly ordered by SSL protection level
secret establishements order (by the TLS stack).
OSSL_FUNC_SSL_QUIC_TLS_yield_secret_fn() (ha_quic_ossl_got_transport_params())
is a simple wrapping function over ha_quic_set_encryption_secrets() which is used
by boringSSL/quictls API.
OSSL_FUNC_SSL_QUIC_TLS_got_transport_params_fn() (ha_quic_ossl_got_transport_params())
role is to store the peer received transport parameters. It simply calls
quic_transport_params_store() and set them into the TLS stack calling
qc_ssl_set_quic_transport_params().
Also add some comments for all the OpenSSL 3.5 QUIC API callbacks.
This patch have no impact on the other use of QUIC API provided by the others TLS
stacks.
If there is an alloc failure during qc_new_conn(), cleaning is done via
quic_conn_release(). However, since the below commit, an unchecked
dereferencing of <qc.path> is performed in the latter.
e841164a4402118bd7b2e2dc2b5068f21de5d9d2
MINOR: quic: account for global congestion window
To fix this, simply check <qc.path> before dereferencing it in
quic_conn_release(). This is safe as it is properly initialized to NULL
on qc_new_conn() first stage.
This does not need to be backported.
quic_conn_release() may, or may not, free the tasklet associated with
the connection. So make it return 1 if it was, and 0 otherwise, so that
if it was called from the tasklet handler itself, the said handler can
act accordingly and return NULL if the tasklet was destroyed.
This should be backported if 9240cd4a2771245fae4d0d69ef025104b14bfc23
is backported.
Use the newly defined cshared type to account for the sum of congestion
window of every QUIC connection. This value is stored in global counter
quic_mem_global defined in proto_quic module.
In quic_conn_app_io_cb, make sure we return NULL if the tasklet has been
destroyed, so that the scheduler knows. It is not yet needed, but will
be soon.
A new structure quic_tune has recently been defined. Its purpose is to
store global options related to QUIC. Previously, only the tunable to
toggle pacing was stored in it.
This commit moves several QUIC related tunable from global to quic_tune
structure. This better centralizes QUIC configuration option and gives
room for future generic options.
Pacing burst size is now dynamic. As such, configuration value has been
removed and related fields in bind_conf and quic_cc_path structures can
be safely removed.
This should be backported up to 3.1.
Pacing was recently implemented by QUIC MUX. Its tasklet is rescheduled
until next emission timer is reached. To improve performance, an
alternate execution of qcc_io_cb was performed when rescheduled due to
pacing. This was implemented using TASK_F_USR1 flag.
However, this model is fragile, in particular when several events
happened alongside pacing scheduling. This has caused some issue
recently, most notably when MUX is subscribed on transport layer on
receive for handshake completion while pacing emission is performed in
parallel. MUX qcc_io_cb() would not execute the default code path, which
means the reception event is silently ignored.
Recent patches have reworked several parts of qcc_io_cb. The objective
was to improve performance with better algorithm on send and receive
part. Most notable, qcc frames list is only cleared when new data is
available for emission. With this, pacing alternative code is now mostly
unneeded. As such, this patch removes it. The following changes are
performed :
* TASK_F_USR1 is now not used by QUIC MUX. As such, tasklet_wakeup()
default invokation can now replace obsolete wrappers
qcc_wakeup/qcc_wakeup_pacing
* qcc_purge_sending is removed. On pacing rescheduling, all qcc_io_cb()
is executed. This is less error-prone, in particular when pacing is
mixed with other events like receive handling. This renders the code
less fragile, as it completely solves the described issue above.
This should be backported up to 3.1.
This patch fixes the loss of information when computing the delivery rate
(quic_cc_drs.c) on links with very low latency due to usage of 32bits
variables with the millisecond as precision.
Initialize the quic_conn task with TASK_F_WANTS_TIME flag ask it to ask
the scheduler to update the call date of this task. This allows this task to get
a nanosecond resolution on the call date calling task_mono_time(). This is enabled
only for congestion control algorithms with delivery rate estimation support
(BBR only at this time).
Store the send date with nanosecond precision of each TX packet into
->time_sent_ns new quic_tx_packet struct member to store the date a packet was
sent in nanoseconds thanks to task_mono_time().
Make use of this new timestamp by the delivery rate estimation algorithm (quic_cc_drs.c).
Rename current ->time_sent member from quic_tx_packet struct to ->time_sent_ms to
distinguish the unit used by this variable (millisecond) and update the code which
uses this variable. The logic found in quic_loss.c is not modified at all.
Must be backported to 3.1.
qc_packet_loss_lookup() aim is to detect the packet losses. This is this function
which must called ->on_pkt_lost() BBR specific callback. It also set
<bytes_lost> passed parameter to the total number of bytes detected as lost upon
an ACK frame receipt for its caller.
Modify qc_release_lost_pkts() to call ->congestion_event() with the send time
from the newest packet detected as lost.
Modify qc_release_lost_pkts() to call ->slow_start() callback only if define
by the congestion control algorithm. This is not the case for BBR.
Define a new QUIC congestion algorithm token 'cubic-pacing' for
quic-cc-algo bind keyword. This is identical to default cubic
implementation, except that pacing is used for STREAM frames emission.
This algorithm supports an extra argument to specify a burst size. This
is stored into a new bind_conf member named quic_pacing_burst which can
be reuse to initialize quic path.
Pacing support is still considered experimental. As such, 'cubic-pacing'
can only be used with expose-experimental-directives set.
