Most of calls to channel_abort() are associated to a call to
channel_auto_close(). Others are in areas where the auto close is the
default. So, it is now systematically enabled when an abort is performed on
a channel, as part of channel_abort() function.
First, it is useless to abort the both channel explicitly. For HTTP streams,
http_reply_and_close() is called. This function already take care to abort
processing. For TCP streams, we can rely on stream_retnclose().
To set termination flags, we can also rely on http_set_term_flags() for HTTP
streams and sess_set_term_flags() for TCP streams. Thus no reason to handle
them by hand.
At the end, the error handling after filters evaluation is now quite simple.
We erroneously though that an attempt to receive data was not possible if the SC
was waiting for more room in the channel buffer. A BUG_ON() was added to detect
bugs. And in fact, it is possible.
The regression was added in commit 341a5783b ("BUG/MEDIUM: stconn: stop to
enable/disable reads from streams via si_update_rx").
This patch should fix the issue #2115. It must be backported if the commit
above is backported.
A regression was introduced when stream's timeouts were refactored. Write
timeouts are not testing is the right order. When timeous of the front SC
are handled, we must then test the read timeout on the request channel and
the write timeout on the response channel. But write timeout is tested on
the request channel instead. On the back SC, the same mix-up is performed.
We must be careful to handle timeouts before checking channel flags. To
avoid any confusions, all timeuts are handled first, on front and back SCs.
Then flags of the both channels are tested.
It is a 2.8-specific issue. No backport needed.
There is a bug at begining of process_stream(). The SE_FL_ERROR flag is
tested against backend stream-connector's flags instead of its SE
descriptor's flags. It is an old typo, introduced when the stream-interfaces
were replaced by the conn-streams.
This patch must be backported as far as 2.6.
Fedora Rawhide is shipped with the most recent compilers, not yet released with
more conservative distro. It is good to catch compile errors on those compilers.
This bug arrived with this commit:
MEDIUM: quic: Ack delay implementation
After having probed the Handshake packet number space, one must not select the
Application encryption level to continue trying building packets as this is done
when the connection is not probing. Indeed, if the ACK timer has been triggered
in the meantime, the packet builder will try to build a packet at the Application
encryption level to acknowledge the received packet. But there is very often
no 01RTT packet to acknowledge when the connection is probing before the
handshake is completed. This triggers a BUG_ON() in qc_do_build_pkt() which
checks that the tree of ACK ranges to be used is not empty.
Thank you to @Tristan971 for having reported this issue in GH #2109.
Must be backported to 2.6 and 2.7.
qel->pktns->tx.pto_probe is set to 0 after having prepared a probing
datagram. There is no reason to check this parameter. Furthermore
it is always 0 when the connection does not probe the peer.
Must be backported to 2.6 and 2.7.
As reported by @Tristan971 in GH #2116, the congestion control window could be zero
due to an inversion in the code about the reduction factor to be applied.
On a new loss event, it must be applied to the slow start threshold and the window
should never be below ->min_cwnd (2*max_udp_payload_sz).
Same issue in both newReno and cubic algorithm. Furthermore in newReno, only the
threshold was decremented.
Must be backported to 2.6 and 2.7.
Add two missing checks not to substract too big values from another too little
one. In this case the resulted wrapped huge values could be passed to the function
which has to remove the last range of a tree of ACK ranges as encoded limit size
not to go below, cancelling the ACK ranges deletion. The consequence could be that
no ACK were sent.
Must be backported to 2.6 and 2.7.
qc_may_build_pkt() has been modified several times regardless of the conditions
the functions it is supposed to allow to send packets (qc_build_pkt()/qc_do_build_pkt())
really use to finally send packets just after having received others, leading
to contraditions and possible very long loops sending empty packets (PADDING only packets)
because qc_may_build_pkt() could allow qc_build_pkt()/qc_do_build_pkt to build packet,
and the latter did nothing except sending PADDING frames, because from its point
of view they had nothing to send.
For now on, this is the job of qc_may_build_pkt() to decide to if there is
packets to send just after having received others AND to provide this information
to the qc_build_pkt()/qc_do_build_pkt()
Note that the unique case where the acknowledgements are completely ignored is
when the endpoint must probe. But at least this is when sending at most two datagrams!
This commit also fixes the issue reported by Willy about a very low throughput
performance when the client serialized its requests.
Must be backported to 2.7 and 2.6.
This should help in diagnosing issues.
Some adjustments have to be done to avoid deferencing a quic_conn objects from
TRACE_*() calls.
Must be backported to 2.7 and 2.6.
Do not ignore very short RTTs (less than 1ms) before computing the smoothed
RTT initializing it to an "infinite" value (UINT_MAX).
Must be backported to 2.7 and 2.6.
Add the number of packet losts and the maximum congestion control window computed
by the algorithms to "show quic".
Same thing for the traces of existent congestion control algorithms.
Must be backported to 2.7 and 2.6.
In fd_update_events(), we loop until there's no bit in the running_mask
that is not in the thread_mask. Problem is, the thread sets its
running_mask bit before that loop, and so if 2 threads do the same, and
a 3rd one just closes the FD and sets the thread_mask to 0, then
running_mask will always be non-zero, and we will loop forever. This is
trivial to reproduce when using a DNS resolver that will just answer
"port unreachable", but could theoretically happen with other types of
file descriptors too.
To fix that, just don't bother looping if we're no longer in the
thread_mask, if that happens we know we won't have to take care of the
FD, anyway.
This should be backported to 2.7, 2.6 and 2.5.
Setting "shards by-group" will create one shard per thread group. This
can often be a reasonable tradeoff between a single one that can be
suboptimal on CPUs with many cores, and too many that will eat a lot
of file descriptors. It was shown to provide good results on a 224
thread machine, with a distribution that was even smoother than the
system's since here it can take into account the number of connections
per thread in the group. Depending on how popular it becomes, it could
even become the default setting in a future version.
Instead of artificially setting the shards count to MAX_THREAD when
"by-thread" is used, let's reserve special values for symbolic names
so that we can add more in the future. For now we use value -1 for
"by-thread", which requires to turn the type to signed int but it was
already used as such everywhere anyway.
fd_migrate_on() can be used to migrate an existing FD to any thread, even
one belonging to a different group from the current one and from the
caller's. All that is needed is to make sure the FD is still valid when
the operation is performed (which is the case when such operations happen).
This is potentially slightly expensive since it locks the tgid during the
delicate operation, but it is normally performed only from an owning
thread to offer the FD to another one (e.g. reassign a better thread upon
accept()).
In order to permit to migrate FDs from one thread group to another,
we'll need to be able to set a TGID that is compatible with no other
thread group. Either we use a special value or we dedicate a special
bit. Given that we already have way more bits than needed, let's just
sacrifice the topmost one to serve as a lock bit, indicating the tgid
is not valid anymore. This will make all fd_grab_tgid() fail to grab
it.
The new fd_lock_tgid() function now tries to assign a locked tgid to
an idle FD, and fd_unlock_tgid() simply drops the lock bit, revealing
the target tgid.
For now it's still unused so it must not have any effect.
fd_claim_tgid() uses a CAS to set the desired TGID on the FD. It's only
called from fd_insert() where in the vast majority of cases, the tgid
and refcount are zero before the call. However the loop was optimized
for the case where it was equal to the desired TGID, systematically
causing one extra round in the loop there. Better start assuming a
zero value.
We're only checking for 0, 1, or >1 groups enabled there, and we'll soon
need to be more precise and know quickly which groups are non-empty.
Let's just replace the count with a mask of enabled groups. This will
allow to quickly spot the presence of any such group in a set.
Alert when the len argument of a stick table type contains incorrect
characters.
Replace atol by strtol.
Could be backported in every maintained versions.
It was missing from the output but is sometimes convenient to observe
and understand how incoming connections are distributed. The CPU usage
is reported as the instant measurement of 100-idle_pct for each thread,
and the average value is shown for the aggregated value.
This could be backported as it's helpful in certain troublehsooting
sessions.
As the ACK frames are not added to the packet list of ack-eliciting frames,
it could not be traced. But there is a flag to identify such packet.
Let's use it to add this information to the traces of TX packets.
Must be backported to 2.6 and 2.7.
Dump at proto level the packet information when its header protection was removed.
Remove no more use qpkt_trace variable.
Must be backported to 2.7 and 2.6.
It is possible that the handshake was not confirmed and there was no more
packet in flight to probe with. It this case the server must wait for
the client to be unblocked without probing any packet number space contrary
to what was revealed by interop tests as follows:
[01|quic|2|uic_loss.c:65] TX loss pktns : qc@0x7fac301cd390 pktns=I pp=0
[01|quic|2|uic_loss.c:67] TX loss pktns : qc@0x7fac301cd390 pktns=H pp=0 tole=-102ms
[01|quic|2|uic_loss.c:67] TX loss pktns : qc@0x7fac301cd390 pktns=01RTT pp=0 if=1054 tole=-1987ms
[01|quic|5|uic_loss.c:73] quic_loss_pktns(): leaving : qc@0x7fac301cd390
[01|quic|5|uic_loss.c:91] quic_pto_pktns(): entering : qc@0x7fac301cd390
[01|quic|3|ic_loss.c:121] TX PTO handshake not already completed : qc@0x7fac301cd390
[01|quic|2|ic_loss.c:141] TX PTO : qc@0x7fac301cd390 pktns=I pp=0 dur=83ms
[01|quic|5|ic_loss.c:142] quic_pto_pktns(): leaving : qc@0x7fac301cd390
[01|quic|3|c_conn.c:5179] needs to probe Initial packet number space : qc@0x7fac301cd390
This bug was not visible before this commit:
BUG/MINOR: quic: wake up MUX on probing only for 01RTT
This means that before it, one could do bad things (probing the 01RTT packet number
space before the handshake was confirmed).
Must be backported to 2.7 and 2.6.
When end-of-stream is reported by a H2 stream, we must take care to also
report an error is end-of-input was not reported. Indeed, it is now
mandatory to set SE_FL_EOI or SE_FL_ERROR flags when SE_FL_EOS is set.
It is a 2.8-specific issue. No backport needed.
When TCP connection is first upgrade to H1 then to H2, the stream-connector,
created by the PT mux, must be destroyed because the H2 mux cannot inherit
from it. When it is performed, the SE_FL_EOS flag is set but SE_FL_EOI must
also be set. It is now required to never set SE_FL_EOS without SE_FL_EOI or
SE_FL_ERROR.
It is a 2.8-specific issue. No backport needed.
Timeouts for dynamic resolutions are not handled at the stream level but by
the resolvers themself. It means there is no connect, client and server
timeouts defined on the internal proxy used by a resolver.
While it is not an issue for DNS resolution over UDP, it can be a problem
for resolution over TCP. New sessions are automatically created when
required, and killed on excess. But only established connections are
considered. Connecting ones are never killed. Because there is no conncet
timeout, we rely on the kernel to report a connection error. And this may be
quite long.
Because resolutions are periodically triggered, this may lead to an excess
of unusable sessions in connecting state. This also prevents HAProxy to
quickly exit on soft-stop. It is annoying, especially because there is no
reason to not set a connect timeout.
So to mitigate the issue, we now use the "resolve" timeout as connect
timeout for the internal proxy attached to a resolver.
This patch should be backported as far as 2.4.
Thanks to previous commit ("BUG/MEDIUM: dns: Kill idle DNS sessions during
stopping stage"), DNS idle sessions are killed on stopping staged. But the
task responsible to kill these sessions is running every 5 seconds. It
means, when HAProxy is stopped, we can observe a delay before the process
exits.
To reduce this delay, when the resolvers task is executed, all DNS idle
tasks are woken up.
This patch must be backported as far as 2.6.
There is no server timeout for DNS sessions over TCP. It means idle session
cannot be killed by itself. There is a task running peridically, every 5s,
to kill the excess of idle sessions. But the last one is never
killed. During the stopping stage, it is an issue since the dynamic
resolutions are no longer performed (2ec6f14c "BUG/MEDIUM: resolvers:
Properly stop server resolutions on soft-stop").
Before the above commit, during stopping stage, the DNS sessions were killed
when a resolution was triggered. Now, nothing kills these sessions. This
prevents the process to finish on soft-stop.
To fix this bug, the task killing excess of idle sessions now kill all idle
sessions on stopping stage.
This patch must be backported as far as 2.6.
When the log applet is executed while a shut is pending, the remaining
output data must always be consumed. Otherwise, this can prevent the stream
to exit, leading to a spinning loop on the applet.
It is 2.8-specific. No backport needed.
When the stats applet is executed while a shut is pending, the remaining
output data must always be consumed. Otherwise, this can prevent the stream
to exit, leading to a spinning loop on the applet.
It is 2.8-specific. No backport needed.
When the http-client applet is executed while a shut is pending, the
remaining output data must always be consumed. Otherwise, this can prevent
the stream to exit, leading to a spinning loop on the applet.
It is 2.8-specific. No backport needed.
When the cli applet is executed while a shut is pending, the remaining
output data must always be consumed. Otherwise, this can prevent the stream
to exit, leading to a spinning loop on the applet.
This patch should fix the issue #2107. It is 2.8-specific. No backport
needed.
An applet must never set SE_FL_EOS flag without SE_FL_EOI or SE_FL_ERROR
flags. Here, SE_FL_EOI flag was missing for "quit" or "_getsocks"
commands. Indeed, these commands are terminal.
This bug triggers a BUG_ON() recently added.
This patch is related to the issue #2107. It is 2.8-specific. No backport
needed.
Released version 2.8-dev7 with the following main changes :
- BUG/MINOR: stats: Don't replace sc_shutr() by SE_FL_EOS flag yet
- BUG/MEDIUM: mux-h2: Be able to detect connection error during handshake
- BUG/MINOR: quic: Missing padding in very short probe packets
- MINOR: proxy/pool: prevent unnecessary calls to pool_gc()
- CLEANUP: proxy: remove stop_time related dead code
- DOC/MINOR: reformat configuration.txt's "quoting and escaping" table
- MINOR: http_fetch: Add support for empty delim in url_param
- MINOR: http_fetch: add case insensitive support for smp_fetch_url_param
- MINOR: http_fetch: Add case-insensitive argument for url_param/urlp_val
- REGTESTS : Add test support for case insentitive for url_param
- BUG/MEDIUM: proxy/sktable: prevent watchdog trigger on soft-stop
- BUG/MINOR: backend: make be_usable_srv() consistent when stopping
- BUG/MINOR: ssl: Remove dead code in cli_parse_update_ocsp_response
- BUG/MINOR: ssl: Fix potential leak in cli_parse_update_ocsp_response
- BUG/MINOR: ssl: ssl-(min|max)-ver parameter not duplicated for bundles in crt-list
- BUG/MINOR: quic: Wrong use of now_ms timestamps (cubic algo)
- MINOR: quic: Add recovery related information to "show quic"
- BUG/MINOR: quic: Wrong use of now_ms timestamps (newreno algo)
- BUG/MINOR: quic: Missing max_idle_timeout initialization for the connection
- MINOR: quic: Implement cubic state trace callback
- MINOR: quic: Adjustments for generic control congestion traces
- MINOR: quic: Traces adjustments at proto level.
- MEDIUM: quic: Ack delay implementation
- BUG/MINOR: quic: Wrong rtt variance computing
- MINOR: cli: support filtering on FD types in "show fd"
- MINOR: quic: Add a fake congestion control algorithm named "nocc"
- CI: run smoke tests on config syntax to check memory related issues
- CLEANUP: assorted typo fixes in the code and comments
- CI: exclude doc/{design-thoughts,internals} from spell check
- BUG/MINOR: quic: Remaining useless statements in cubic slow start callback
- BUG/MINOR: quic: Cubic congestion control window may wrap
- MINOR: quic: Add missing traces in cubic algorithm implementation
- BUG/MAJOR: quic: Congestion algorithms states shared between the connection
- BUG/MINOR: ssl: Undefined reference when building with OPENSSL_NO_DEPRECATED
- BUG/MINOR: quic: Remove useless BUG_ON() in newreno and cubic algo implementation
- MINOR: http-act: emit a warning when a header field name contains forbidden chars
- DOC: config: strict-sni allows to start without certificate
- MINOR: quic: Add trace to debug idle timer task issues
- BUG/MINOR: quic: Unexpected connection closures upon idle timer task execution
- BUG/MINOR: quic: Wrong idle timer expiration (during 20s)
- BUILD: quic: 32bits compilation issue in cli_io_handler_dump_quic()
- BUG/MINOR: quic: Possible wrong PTO computing
- BUG/MINOR: tcpcheck: Be able to expect an empty response
- BUG/MEDIUM: stconn: Add a missing return statement in sc_app_shutr()
- BUG/MINOR: stream: Fix test on channels flags to set clientfin/serverfin touts
- MINOR: applet: Uninline appctx_free()
- MEDIUM: applet/trace: Register a new trace source with its events
- CLEANUP: stconn: Remove remaining debug messages
- BUG/MEDIUM: channel: Improve reports for shut in co_getblk()
- BUG/MEDIUM: dns: Properly handle error when a response consumed
- MINOR: stconn: Remove unecessary test on SE_FL_EOS before receiving data
- MINOR: stconn/channel: Move CF_READ_DONTWAIT into the SC and rename it
- MINOR: stconn/channel: Move CF_SEND_DONTWAIT into the SC and rename it
- MINOR: stconn/channel: Move CF_NEVER_WAIT into the SC and rename it
- MINOR: stconn/channel: Move CF_EXPECT_MORE into the SC and rename it
- MINOR: mux-pt: Report end-of-input with the end-of-stream after a read
- BUG/MINOR: mux-h1: Properly report EOI/ERROR on read0 in h1_rcv_pipe()
- CLEANUP: mux-h1/mux-pt: Remove useless test on SE_FL_SHR/SE_FL_SHW flags
- MINOR: mux-h1: Report an error to the SE descriptor on truncated message
- MINOR: stconn: Always ack EOS at the end of sc_conn_recv()
- MINOR: stconn/applet: Handle EOI in the applet .wake callback function
- MINOR: applet: No longer set EOI on the SC
- MINOR: stconn/applet: Handle EOS in the applet .wake callback function
- MEDIUM: cache: Use the sedesc to report and detect end of processing
- MEDIUM: cli: Use the sedesc to report and detect end of processing
- MINOR: dns: Remove the test on the opposite SC state to send requests
- MEDIUM: dns: Use the sedesc to report and detect end of processing
- MEDIUM: spoe: Use the sedesc to report and detect end of processing
- MEDIUM: hlua/applet: Use the sedesc to report and detect end of processing
- MEDIUM: log: Use the sedesc to report and detect end of processing
- MEDIUM: peers: Use the sedesc to report and detect end of processing
- MINOR: sink: Remove the tests on the opposite SC state to process messages
- MEDIUM: sink: Use the sedesc to report and detect end of processing
- MEDIUM: stats: Use the sedesc to report and detect end of processing
- MEDIUM: promex: Use the sedesc to report and detect end of processing
- MEDIUM: http_client: Use the sedesc to report and detect end of processing
- MINOR: stconn/channel: Move CF_EOI into the SC and rename it
- MEDIUM: tree-wide: Move flags about shut from the channel to the SC
- MINOR: tree-wide: Simplifiy some tests on SHUT flags by accessing SCs directly
- MINOR: stconn/applet: Add BUG_ON_HOT() to be sure SE_FL_EOS is never set alone
- MINOR: server: add SRV_F_DELETED flag
- BUG/MINOR: server/del: fix srv->next pointer consistency
- BUG/MINOR: stats: properly handle server stats dumping resumption
- BUG/MINOR: sink: free forward_px on deinit()
- BUG/MINOR: log: free log forward proxies on deinit()
- MINOR: server: always call ssl->destroy_srv when available
- MINOR: server: correctly free servers on deinit()
- BUG/MINOR: hlua: hook yield does not behave as expected
- MINOR: hlua: properly handle hlua_process_task HLUA_E_ETMOUT
- BUG/MINOR: hlua: enforce proper running context for register_x functions
- MINOR: hlua: Fix two functions that return nothing useful
- MEDIUM: hlua: Dynamic list of frontend/backend in Lua
- MINOR: hlua_fcn: alternative to old proxy and server attributes
- MEDIUM: hlua_fcn: dynamic server iteration and indexing
- MEDIUM: hlua_fcn/api: remove some old server and proxy attributes
- CLEANUP: hlua: fix conflicting comment in hlua_ctx_destroy()
- MINOR: hlua: add simple hlua reference handling API
- MINOR: hlua: fix return type for hlua_checkfunction() and hlua_checktable()
- BUG/MINOR: hlua: fix reference leak in core.register_task()
- BUG/MINOR: hlua: fix reference leak in hlua_post_init_state()
- BUG/MINOR: hlua: prevent function and table reference leaks on errors
- CLEANUP: hlua: use hlua_ref() instead of luaL_ref()
- CLEANUP: hlua: use hlua_pushref() instead of lua_rawgeti()
- CLEANUP: hlua: use hlua_unref() instead of luaL_unref()
- MINOR: hlua: simplify lua locking
- BUG/MEDIUM: hlua: prevent deadlocks with main lua lock
- MINOR: hlua_fcn: add server->get_rid() method
- MINOR: hlua: support for optional arguments to core.register_task()
- DOC: lua: silence "literal block ends without a blank line" Sphinx warnings
- DOC: lua: silence "Unexpected indentation" Sphinx warnings
- BUG/MINOR: event_hdl: fix rid storage type
- BUG/MINOR: event_hdl: make event_hdl_subscribe thread-safe
- MINOR: event_hdl: global sublist management clarification
- BUG/MEDIUM: event_hdl: clean soft-stop handling
- BUG/MEDIUM: event_hdl: fix async data refcount issue
- MINOR: event_hdl: normal tasks support for advanced async mode
- MINOR: event_hdl: add event_hdl_async_equeue_isempty() function
- MINOR: event_hdl: add event_hdl_async_equeue_size() function
- MINOR: event_hdl: pause/resume for subscriptions
- MINOR: proxy: add findserver_unique_id() and findserver_unique_name()
- MEDIUM: hlua/event_hdl: initial support for event handlers
- MINOR: hlua/event_hdl: per-server event subscription
- EXAMPLES: add basic event_hdl lua example script
- MINOR: http-ana: Add a HTTP_MSGF flag to state the Expect header was checked
- BUG/MINOR: http-ana: Don't switch message to DATA when waiting for payload
- BUG/MINOR: quic: Possible crashes in qc_idle_timer_task()
- MINOR: quic: derive first DCID from client ODCID
- MINOR: quic: remove ODCID dedicated tree
- MINOR: quic: remove address concatenation to ODCID
- BUG/MINOR: mworker: unset more internal variables from program section
- BUG/MINOR: errors: invalid use of memprintf in startup_logs_init()
- MINOR: applet: Use unsafe version to get stream from SC in the trace function
- BUG/MUNOR: http-ana: Use an unsigned integer for http_msg flags
- MINOR: compression: Make compression offload a flag
- MINOR: compression: Prepare compression code for request compression
- MINOR: compression: Store algo and type for both request and response
- MINOR: compression: Count separately request and response compression
- MEDIUM: compression: Make it so we can compress requests as well.
- BUG/MINOR: lua: remove incorrect usage of strncat()
- CLEANUP: tcpcheck: remove the only occurrence of sprintf() in the code
- CLEANUP: ocsp: do no use strpcy() to copy a path!
- CLEANUP: tree-wide: remove strpcy() from constant strings
- CLEANUP: opentracing: remove the last two occurrences of strncat()
- BUILD: compiler: fix __equals_1() on older compilers
- MINOR: compiler: define a __attribute__warning() macro
- BUILD: bug.h: add a warning in the base API when unsafe functions are used
- BUG/MEDIUM: listeners: Use the right parameters for strlcpy2().
When calls to strcpy() were replaced with calls to strlcpy2(), one of them
was replaced wrong, and the source and size were inverted. Correct that.
This should fix issue #2110.
Once in a while we introduce an sprintf() or strncat() function by
accident. These ones are particularly dangerous and must never ever
be used because the only way to use them safely is at least as
complicated if not more, than their safe counterparts. By redefining
a few of these functions with an attribute_warning() we can deliver a
message to the developer who is tempted to use them. This commit does
it for strcat(), strcpy(), strncat(), sprintf(), vsprintf(). More could
come later if needed, such as strtok() and maybe a few others, but these
are less common.
__attribute__((deprecated)) is convenient to discourage from using
something deprecated, but gcc >= 4.3 provides __attribute__((warning(x)))
that allows to display a specific warning if something is used. This is
particularly convenient to give indications when some API parts need to
be adapted. Let's just define it as a macro that falls back to the older
deprecated attribute when not available.
It's supported on clang 14 as well but works differently and errors
out when redefined (while the main purpose precisely is to add such a
redefinition). Thus instead on clang we use deprecated(msg) which is
OK. See https://github.com/llvm/llvm-project/issues/56519
It appeared that __has_attribute() doesn't work on gcc 4.4 and older
because the concatenation of __has_attribute##x isn't resolved as a one
before being passed to __equals_1() which immediately concatenates it to
comma_for_one. We first need to pass it through an extra layer to resolve
this name to a value. The new version was tested with gcc 4.2 to 11.3.
This may be backported though it's pretty minor.
In flt_ot_sample_to_str() there were two occurrences of strncat() which
are used to copy N chars from the source and append a zero. For the sake
of definitely getting rid of this nasty function let's replace them by
memcpy() instead. It's worth noting that the length test there appeared
to be incorrect as it didn't make provisions for the trailing zero,
unless the size argument doesn't take it into account (seems unlikely).
Nothing was changed regarding this. If the code was good, it still is,
otherwise if it was bad it still is. At least this is more obvious now
than when using a function that needs n+1 chars to work.
