quic_connect_server(), tcp_connect_server(), uxst_connect_server() duplicate
same code to check different ERRNOs, that socket() and setns() may return.
They also duplicate some runtime condition checks, applied to the obtained
server socket fd.
So, in order to remove these duplications and to improve code readability,
let's encapsulate socket() and setns() ERRNOs handling in
sock_handle_system_err(). It must be called just before fd's runtime condition
checks, which we also move in sock_create_server_socket by the same reason.
As UNIX Domain sockets could be attached to Linux namespaces (see more details
about it from the Linux kernel patch set below:
https://lore.kernel.org/netdev/m1hbl7hxo3.fsf@fess.ebiederm.org),
it is better to use sock_create_server_socket() in UNIX stream protocol
implementation, as this function calls my_socket_at() and the latter takes
in account server network namespace, which could be configured as in example
below:
backend be_bar
...
server rpicam0 /run/ustreamer.sock namespace foonet
So, for UNIX Domain socket, used as an address of some backend server, this
patch makes possible to perform connect() to this backend server from the same
network namespace, where the server is running, or where its listening socket
was created.
Using sock_create_server_socket() in UNIX stream protocol implementation also
makes the code of uxst_connect_server() more uniform with tcp_connect_server()
and quic_connect_server().
It's not strictly necessary, but it's still better to avoid setting
up the same socket multiple times when it's being duplicated to a few
FDs. We don't change that for inherited ones however since they may
really need to be set up, so we only skip duplicated ones.
In sock_unix_bind_receiver(), uxst_bind_listener() and uxdg_bind_listener(),
properly dump ABNS socket names by leveraging sa2str() function which does the
hard work for us.
UNIX sockets are reported as is (unchanged) while ABNS UNIX sockets
are prefixed with 'abns@' to match the syntax used in config file.
(they where previously showing as empty strings because of the leading
NULL-byte that was not properly handled in this case)
This is only a minor debug improvement, however it could be useful to
backport it up to 2.4.
[for 2.4: you should replace "%s [%s]" by "%s for [%s]" for uxst and uxgd if
you wan't the patch to apply properly]
When a listener is suspended, we expect that it may not process any data for
the time it is suspended.
Yet for named UNIX socket, as the suspend operation is a no-op at the proto
level, recv events on the socket may still be processed by the polling loop.
This is quite disturbing as someone may rely on a paused proxy being harmless,
which is true for all protos except for named UNIX sockets.
To fix this behavior, we explicitely disable io recv events when suspending a
named UNIX socket listener (we call disable() method on the listener).
The io recv events will automatically be restored when the listener is resumed
since the l->enable() method is called at the end of the resume() operation.
This could be backported up to 2.4 after a reasonable observation
period to make sure that this change doesn't cause unwanted side-effects.
resume method was not explicitly defined for uxst protocol family.
Here we can safely use the default_resume_listener, just like the uxdg family.
This could be backported up to 2.4.
In uxst_bind_listener() and uxdg_bind_listener(), when the function
fails because the listener is not bound, both function are setting
the error message but don't set the err status before returning.
Because of this, such error is not properly handled by the upper functions.
Making sure this error is properly catched by returning a composition of
ERR_FATAL and ERR_ALERT.
This could be backported up to 2.4.
There's been some great confusion between proto_type, ctrl_type and
sock_type. It turns out that ctrl_type was improperly chosen because
it's not the control layer that is of this or that type, but the
transport layer, and it turns out that the transport layer doesn't
(normally) denaturate the underlying control layer, except for QUIC
which turns dgrams to streams. The fact that the SOCK_{DGRAM|STREAM}
set of values was used added to the confusion.
Let's replace it with xprt_type which reuses the later introduced
PROTO_TYPE_* values, and update the comments to explain which one
works at what level.
Just like for the conn_stream, now that these addresses are dynamically
allocated, there is no single case where the pointer is set without the
corresponding flag, and the flag is used as a permission to dereference
the pointer. Let's just replace the test of the flag with a test of the
pointer and remove all flag assignment. This makes the code clearer
(especially in "if" conditions) and saves the need for future code to
think about properly setting the flag after setting the pointer.
Some of the protocol-level ->connect() functions currently dereference
the connection's destination address while others test it and return an
error. There's normally no more non-bogus code path that calls such
functions without a valid destination address on the connection, so
let's unify these functions and just place a BUG_ON() there, and drop
the useless test that's supposed to return an internal error.
This gets rid of most open-coded fcntl() calls, some of which were passed
through DISGUISE() to avoid a useless test. The FD_CLOEXEC was most often
set without preserving previous flags, which could become a problem once
new flags are created. Now this will not happen anymore.
Some older systems may routinely return EWOULDBLOCK for some syscalls
while we tend to check only for EAGAIN nowadays. Modern systems define
EWOULDBLOCK as EAGAIN so that solves it, but on a few older ones (AIX,
VMS etc) both are different, and for portability we'd need to test for
both or we never know if we risk to confuse some status codes with
plain errors.
There were few entries, the most annoying ones are the switch/case
because they require to only add the entry when it differs, but the
other ones are really trivial.
At many places we use construct such as:
if (objt_server(blah))
do_something(objt_server(blah));
At -O2 the compiler manages to simplify the operation and see that the
second one returns the same result as the first one. But at -O1 that's
not always the case, and the compiler is able to emit a second
expression and sees the potential null that results from it, and may
warn about a potential null deref (e.g. with gcc-6.5). There are two
solutions to this:
- either the result of the first test has to be passed to a local
variable
- or the second reference ought to be unchecked using the __objt_*
variant.
This patch fixes all occurrences at once by taking the second approach
(the least intrusive). For constructs like:
objt_server(blah) ? objt_server(blah)->name : "no name"
a macro could be useful. It would for example take the object type
(server), the field name (name) and the default value. But there
are probably not enough occurrences across the whole code for this
to really matter.
This should be backported wherever it applies.
The protocol selection is currently performed based on the family,
control type and socket type. But this is often not enough, as both
only provide DGRAM or STREAM, leaving few variants. Protocols like
SCTP for example might be indistinguishable from TCP here. Same goes
for TCP extensions like MPTCP.
This commit introduces a new enum proto_type that is placed in each
and every protocol definition, that will usually more or less match
the sock_type, but being an enum, will support additional values.
Some protocols fail with "error blah [ip:port]" and other fail with
"[ip:port] error blah". All this already appears in a "starting" or
"binding" context after a proxy name. Let's choose a more universal
approach like below where the ip:port remains at the end of the line
prefixed with "for".
[WARNING] (18632) : Binding [binderr.cfg:10] for proxy http: cannot bind receiver to device 'eth2' (No such device) for [0.0.0.0:1080]
[WARNING] (18632) : Starting [binderr.cfg:10] for proxy http: cannot set MSS to 12 for [0.0.0.0:1080]
No need to keep this flag apart any more, let's merge it into the global
state. The CLI's output state was extended to 6 digits and the linger/cloned
flags moved inside the parenthesis.
Introduce a new XPRT method, start(). The init() method will now only
initialize whatever is needed for the XPRT to run, but any action the XPRT
has to do before being ready, such as handshakes, will be done in the new
start() method. That way, we will be sure the full stack of xprt will be
initialized before attempting to do anything.
The init() call is also moved to conn_prepare(). There's no longer any reason
to wait for the ctrl to be ready, any action will be deferred until start(),
anyway. This means conn_xprt_init() is no longer needed.
Right now the connection subscribe/unsubscribe code needs to manipulate
FDs, which is not compatible with QUIC. In practice what we need there
is to be able to either subscribe or wake up depending on readiness at
the moment of subscription.
This commit introduces two new functions at the control layer, which are
provided by the socket code, to check for FD readiness or subscribe to it
at the control layer. For now it's not used.
This is what we need to drain pending incoming data from an connection.
The code was taken from conn_sock_drain() without the connection-specific
stuff. It still takes a connection for now for API simplicity.
Currnetly conn_ctrl_init() does an fd_insert() and conn_ctrl_close() does an
fd_delete(). These are the two only short-term obstacles against using a
non-fd handle to set up a connection. Let's have pur these into the protocol
layer, along with the other connection-level stuff so that the generic
connection code uses them instead. This will allow to define new ones for
other protocols (e.g. QUIC).
Since we only support regular sockets at the moment, the code was placed
into sock.c and shared with proto_tcp, proto_uxst and proto_sockpair.
For the sake of an improved readability, let's group the protocol
field members according to where they're supposed to be defined:
- connection layer (note: for now even UDP needs one)
- binding layer
- address family
- socket layer
Nothing else was changed.
The various protocols were made static since there was no point in
exporting them in the past. Nowadays with QUIC relying on UDP we'll
significantly benefit from UDP being exported and more generally from
being able to declare some functions as being the same as other
protocols'.
In an ideal world it should not be these protocols which should be
exported, but the intermediary levels:
- socket layer (sock.c only right now), already exported as functions
but nothing structured at the moment ;
- family layer (sock_inet, sock_unix, sockpair etc): already structured
and exported
- binding layer (the part that relies on the receiver): currently fused
within the protocol
- connectiong layer (the part that manipulates connections): currently
fused within the protocol
- protocol (connection's control): shouldn't need to be exposed
ultimately once the elements above are in an easily sharable way.
This field used to be needed before commit 2b5e0d8b6 ("MEDIUM: proto_udp:
replace last AF_CUST_UDP* with AF_INET*") as it was used as a protocol
entry selector. Since this commit it's always equal to the socket family's
value so it's entirely redundant. Let's remove it now to simplify the
protocol definition a little bit.
With the removal of the family-specific port setting, all protocol had
exactly the same implementation of ->add(). A generic one was created
with the name "default_add_listener" so that all other ones can now be
removed. The API was slightly adjusted so that the protocol and the
listener are passed instead of the listener and the port.
Note that all protocols continue to provide this ->add() method instead
of routinely calling default_add_listener() from create_listeners(). This
makes sure that any non-standard protocol will still be able to intercept
the listener addition if needed.
This could be backported to 2.3 along with the few previous patches on
listners as a pure code cleanup.
We used to refrain from calling fd_want_recv() if fd_updt was not allocated
but it's not the right solution as this does not allow the FD to be set.
Instead, let's use the new fd_want_recv_safe() which will update the FD and
create an update entry only if possible. In addition, the equivalent test
before calling fd_stop_recv() was removed as totally useless since there's
not fd_updt creation in this case.
Now we define a new sock_accept_iocb() for socket-based stream protocols
and use it as a wrapper for listener_accept() which now takes a listener
and not an FD anymore. This will allow the receiver's I/O cb to be
redefined during registration, and more specifically to get rid of the
hard-coded hacks in protocol_bind_all() made for syslog.
The previous ->accept() callback in the protocol was removed since it
doesn't have anything to do with accept() anymore but is more generic.
A few places where listener_accept() was compared against the FD's IO
callback for debugging purposes on the CLI were updated.
The socket-specific accept() code in listener_accept() has nothing to
do there. Let's move it to sock.c where it can be significantly cleaned
up. It will now directly return an accepted connection and provide a
status code instead of letting listener_accept() deal with various errno
values. Note that this doesn't support the sockpair specific code.
The function is now responsible for dealing with its own receiver's
polling state and calling fd_cant_recv() when facing EAGAIN.
One tiny change from the previous implementation is that the connection's
sockaddr is now allocated before trying accept(), which saves a memcpy()
of the resulting address for each accept at the expense of a cheap
pool_alloc/pool_free on the final accept returning EAGAIN. This still
apparently slightly improves accept performance in microbencharks.
This call was introduced by commit 5ced3e887 ("MINOR: sock: add
sock_accept_conn() to test a listening socket") but is actually quite
confusing because it makes one think the socket will accept a connection
(which is what we want to have in a new function) while it only tells
whether it's configured to accept connections. Let's call it
sock_accepting_conn() instead.
The same change was applied to sockpair which had the same issue.
Now we introdce a new .rx_listening() function to report if a receiver is
actually a listening socket. The reason for this is to help detect shared
sockets that might have been broken by sibling processes.
Now we have ->suspend() and ->resume() for listeners at the protocol
level. This means that it now becomes possible for a protocol to redefine
its own way to suspend and resume. The default functions are provided for
TCP, UDP and unix, and they are pass-through to the receiver equivalent
as it used to be till now. Nothing was defined for sockpair since it does
not need to suspend/resume during reloads, hence it will succeed.
The inner part now goes into the protocol and is used to decide how to
unbind a given protocol's listener. The existing code which is able to
also unbind the receiver was provided as a default function that we
currently use everywhere. Some complex listeners like QUIC will use this
to decide how to unbind without impacting existing connections, possibly
by setting up other incoming paths for the traffic.
This is used as a generic way to unbind a receiver at the end of
do_unbind_listener(). This allows to considerably simplify that function
since we can now let the protocol perform the cleanup. The generic code
was moved to sock.c, along with the conditional rx_disable() call. Now
the code also supports that the ->disable() function of the protocol
which acts on the listener performs the close itself and adjusts the
RX_F_BUOND flag accordingly.
And also remove it from its callers. This subtle distinction was added as
sort of a hack for the seamless reload feature but is not needed anymore
since the do_close turned unused since commit previous commit ("MEDIUM:
listener: let do_unbind_listener() decide whether to close or not").
This also removes the unbind_listener_no_close() function.
These methods will be used to enable/disable accepting new connections
so that listeners do not play with FD directly anymore. Since all the
currently supported protocols work on socket for now, these are identical
to the rx_enable/rx_disable functions. However they were not defined in
sock.c since it's likely that some will quickly start to differ. At the
moment they're not used.
We have to take care of fd_updt before calling fd_{want,stop}_recv()
because it's allocated fairly late in the boot process and some such
functions may be called very early (e.g. to stop a disabled frontend's
listeners).
These methods will be used to enable/disable rx at the receiver level so
that callers don't play with FDs directly anymore. All our protocols use
the generic ones from sock.c at the moment. For now they're not used.
The ->pause method is inappropriate since it doesn't exactly "pause" a
listener but rather temporarily disables it so that it's not visible at
all to let another process take its place. The term "suspend" is more
suitable, since the "pause" is actually what we'll need to apply to the
FULL and LIMITED states which really need to make a pause in the accept
process. And it goes well with the use of the "resume" function that
will also need to be made per-protocol.
Let's rename the function and make it act on the receiver since it's
already what it essentially does, hence the prefix "_rx" to make it
more explicit.
The protocol struct was a bit reordered because it was becoming a real
mess between the parts related to the listeners and those for the
receivers.
Since the listeners were split into receiver+listener, this field ought
to have been renamed because it's confusing. It really links receivers
and not listeners, as most of the time it's used via rx.proto_list!
The nb_listeners field was updated accordingly.
fd_stop_recv() has nothing to do in the generic listener code, it's per
protocol as some don't need it. For instance with abns@ it could even
lead to fd_stop_recv(-1). And later with QUIC we don't want to touch
the fd at all! It used to be that since commit f2cb169487 delegating
fd manipulation to their respective threads it wasn't possible to call
it down there but it's not the case anymore, so let's perform the action
in the protocol-specific code.
This function is used as a wrapper to set a listener's state everywhere.
We'll use it later to maintain some counters in a consistent state when
switching state so it's capital that all state changes go through it.
No functional change was made beyond calling the wrapper.
This one will be needed to more accurately select a protocol. It may
differ from the socket type for QUIC, which uses dgram at the socket
layer and provides stream at the control layer. The upper level requests
a control layer only so we need this field.
This removes the following fields from struct protocol that are now
retrieved from the protocol family instead: .sock_family, .sock_addrlen,
.l3_addrlen, .addrcmp, .bind, .get_src, .get_dst.
This also removes the UDP-specific udp{,6}_get_{src,dst}() functions
which were referenced but not used yet. Their goal was only to remap
the original AF_INET* addresses to AF_CUST_UDP*.
Note that .sock_domain is still there as it's used as a selector for
the protocol struct to be used.
We need to specially handle protocol families which regroup common
functions used for a given address family. These functions include
bind(), addrcmp(), get_src() and get_dst() for now. Some fields are
also added about the address family, socket domain (protocol family
passed to the socket() syscall), and address length.
These protocol families are referenced from the protocols but not yet
used.
All protocol's listeners now only take care of themselves and not of
the receiver anymore since that's already being done in proto_bind_all().
Now it finally becomes obvious that UDP doesn't need a listener, as the
only thing it does is to set the listener's state to LI_LISTEN!
This removes all the AF_UNIX-specific code from uxst_bind_listener()
and now simply relies on sock_unix_bind_listener() to do the same
job. As mentionned in previous commit, the only difference is that
now an unlikely failure on listen() will not result in a roll back
of the temporary socket names since they will have been renamed
during the bind() operation (as expected). But such failures do not
correspond to any normal case and mostly denote operating system
issues so there's no functionality loss here.
This function performs all the bind-related stuff for UNIX sockets that
was previously done in uxst_bind_listener(). There is a very tiny
difference however, which is that previously, in the unlikely event
where listen() would fail, it was still possible to roll back the binding
and rename the backup to the original socket. Now we have to rename it
before calling returning, hence it will be done before calling listen().
However, this doesn't cover any particular use case since listen() has no
reason to fail there (and the rollback is not done for inherited sockets),
that was just done that way as a generic error processing path.
The code is not used yet and is referenced in the uxst proto's ->bind().
