There are some places in passt/pasta which #include <assert.h> and make
various assertions. If we hit these something has already gone wrong, but
they're there so that we a useful message instead of cryptic misbehaviour
if assumptions we thought were correct turn out not to be.
Except.. the glibc implementation of assert() uses syscalls that aren't in
our seccomp filter, so we'll get a SIGSYS before it actually prints the
message. Work around this by adding our own ASSERT() implementation using
our existing err() function to log the message, and an abort(). The
abort() probably also won't work exactly right with seccomp, but once we've
printed the message, dying with a SIGSYS works just as well as dying with
a SIGABRT.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Two places in passt need to read files line by line (one parsing
resolv.conf, the other parsing /proc/net/*. They can't use fgets()
because in glibc that can allocate memory. Instead they use an
implementation line_read() in util.c. This has some problems:
* It has two completely separate modes of operation, one buffering
and one not, the relation between these and how they're activated
is subtle and confusing
* At least in non-buffered mode, it will mishandle an empty line,
folding them onto the start of the next non-empty line
* In non-buffered mode it will use lseek() which prevents using this
on non-regular files (we don't need that at present, but it's a
surprising limitation)
* It has a lot of difficult to read pointer mangling
Add a new cleaner implementation of allocation-free line-by-line
reading in lineread.c. This one always buffers, using a state
structure to keep track of what we need. This is larger than I'd
like, but it turns out handling all the edge cases of line-by-line
reading in C is surprisingly hard.
This just adds the code, subsequent patches will change the existing
users of line_read() to the new implementation.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
