We never know, maybe there's some spurious POLLIN and read() will fail
with EAGAIN even though we saw POLLIN. Handle that.
(this can happen if we area not the only process reading from the tty,
or in case of hups and such).
Fixes: #35499
This makes use of the new TIOCGPTPEER pty ioctl() for directly opening a
PTY peer, without going via path names. This is nice because it closes a
race around allocating and opening the peer. And also has the nice
benefit that if we acquired an fd originating from some other
namespace/container, we can directly derive the peer fd from it, without
having to reenter the namespace again.
OSC sequences can be closed with one of three terminators:
1. ASCII code 7, aka BEL, aka ^G, aka \x07, aka \a
2. ASCII code 156, aka \x9c
2. Pair of ASCII code 27 followed by ASCII code 92, aka \x1b\x5c
Of these, in some corner case scenarios BEL makes problem (see #34604).
Hence switch away from that wherever we use it, and prefer the \x1b\x5c
instead. That's preferable over \x9c, since the latter is also a valid
UTF-8 codepoint. See discussion here for example:
https://gist.github.com/egmontkob/eb114294efbcd5adb1944c9f3cb5feda#the-escape-sequenceFixes: #34604
Various fixes:
1. Adds O_CLOEXEC for two socketpair()s where we forgot it.
2. Uses FORK_WAIT instead of manual wait_for_terminate_and_check()
invocations.
3. Prefix opaque NULL/0 arguments with comments what they are.
4. Add a banch of assert()s, and change flag validation in
open_terminal() to be assert() (since flags mistakes are programming
errors, not runtime errors).
Let's provide a mechanism to select the number of screen columns for
rebreaking comments in Varlink IDL connected to a TTY, by honouring the
$COLUMNS env var then too. Previously we'd only honour when connected to
a TTY, but it's also useful otherwise for rebreaking ridiculously long
comments, hence honour it in this case too.
let's instead generate ENOTTY on our own. This is more correct with out
coding style (since we generally do not propagate errors via errno), and
also addresses #34039 as side effect. (#34039 really needs to be fixed
in musl though, too, this is just a work-around as side-effect).
Fixes: #34039
glibc returs EIO on ttys that are hung up. That's not really correct,
POSIX seems to disagree.
Work around this in our code, and turn this into a clean "1", since a
hung up tty doesn't stop being a tty just because it is hung up.
Background: https://github.com/systemd/systemd/pull/34039
When pid 1 crashes, the getty unit for the console will happily keep
running which means we end up with two shells competing for the same
tty. Let's call vhangup on /dev/console to kill every other process
attached to the console before we spawn the crash shell. The getty
units have Restart=always but lucky for us, pid 1 just crashed in fire
and flames so it isn't actually able to restart the getty unit.
Various tty types come up with cols/rows not initialized (i.e. set to
zero). Let's detect these cases, and return a better error than EIO,
simply to make things easier to debug.
/dev/console is sometimes a symlink in container managers. Let's handle
that correctly, and resolve the symlink, and not consider the data from
/sys/ in that case.
It doesn't really make sense to have that in dev-setup.c, which is
mostly about setting up /dev/, creating device nodes and stuff.
let's move it to the other stuff that deals with /dev/console's
peculiarities.
Numerous fixes:
1. use vtnr_from_tty() to parse out VT number from tty path
2. open tty for write only when we want to output just ansi sequences
3. open tty in asynchronous mode, and apply a timeout, just to be safe
4. propagate error from writing (most callers ignore it anyway, might as
well pass it along correctly)
This is a lot of stuff, and sometimes quite wild, let's turn this into
its own header.
All stuff color-related that just generates sequences is now in
ansi-color.h (no .c file!), and everything more complex that
probes/ineracts with terminals remains in termina-util.[ch]
Let's update the commentary a bit. Also, use a time-out of 100ms rather
than 50ms for this, simply to unify on the same value used in
vt_disallocate() in a similar case.
Let's put "terminal_" as prefix, like with the other reset calls, and
let's make clear that this only encapsulates the ioctl-based reset
logic, not the ANSI sequence based reset logic.
ESC c is a (vaguely defined) "reset to initial state" ANSI sequence.
Many terminals clear the screen in this case, but that's a bit drastic I
think for most resets.
ESC c was added to the reset logic in
00bc83a275 (i.e. very recently), and I
don't think the effect was clear at that time.
Let's keep the ESC c in place however when we actually want to clear the
screen. Hence move it from reset_terminal_fd() into vt_disallocate().
Fixes: #33689
When we are talking to a serial terminal quite commonly the dimensions
are not set properly, because the serial protocol has not handshake or
similar to transfer this information.
However, we can derive the dimensions via ANSI sequences too, which
should get us the right information, since ANSI sequences are
interpreted by the final terminal, rather than an intermediary local tty
driver (which is where TIOCGWINSZ is interpreted).
This adds a helper call that gets the dimensions this way.
Let's prefix these functions with the subsystem name, and clean them up
a bit. Specifically, drop the error logging, it's entirely duplicative,
since every single caller does it anyway.
Let's add an extra safety check: before issuing the ansi sequence to
query the bg color, let's make sure input and output fd actually
reference the same tty. because otherwise it's unlikely we'll be able to
read back the response from the tty driver.
This is mostly just paranoia.
If we only read partial information from the tty we ended up parsing it
again and again, confusing the state machine. hence, return how much
data we actually processed and drop it from the buffer.
Lennart Poettering
Mike Yuan
Luca Boccassi
Daan De Meyer
Michael Ferrari