This is a rework of #24764 by Cristian Rodríguez
<crodriguez@owncloud.com>, which stalled.
Instead of assigning -1 we'll use a macro defined to INT_MAX however.
The cmd(3) man page says about CMSG_DATA():
> The pointer returned cannot be assumed to be suitably aligned for
> accessing arbitrary payload data types. Applications should not cast
> it to a pointer type matching the payload, but should instead use
> memcpy(3) to copy data to or from a suitably declared object.
Hence, if we want to use unaligned data in cmsg, we need to copy it
before use. That's typically important for reading timestamps in
RISCV32, as the time_t is 64bit and size_t is 32bit on the system.
Apparently CMSG_DATA() alignment is very much undefined. Which is quite
an ABI fuck-up, but we need to deal with this. CMSG_TYPED_DATA() already
checks alignment of the specified pointer. Let's also check matching
alignment of the underlying structures, which we already can do at
compile-time.
See: #27241
(This does not fix#27241, but should catch such errors already at
compile-time instead of runtime)
This is a short helper for connecting to AF_UNIX sockets in the file
system. It works around the 108ch limit of sockaddr_un, and supports
"at" style fds.
This doesn't come with a test of its own, but the next patch will add
that.
It does the same stuff, let's use the same codepaths as much as we can.
And while we are at it, let's generate good error codes in case we are
called with unsupported parameters/let's validate stuff more that might
originate from user input.
In general we almost never hit those asserts in production code, so users see
them very rarely, if ever. But either way, we just need something that users
can pass to the developers.
We have quite a few of those asserts, and some have fairly nice messages, but
many are like "WTF?" or "???" or "unexpected something". The error that is
printed includes the file location, and function name. In almost all functions
there's at most one assert, so the function name alone is enough to identify
the failure for a developer. So we don't get much extra from the message, and
we might just as well drop them.
Dropping them makes our code a tiny bit smaller, and most importantly, improves
development experience by making it easy to insert such an assert in the code
without thinking how to phrase the argument.
[59/1551] Compiling C object src/basic/libbasic.a.p/socket-util.c.o
../src/basic/socket-util.c: In function ‘socket_get_mtu’:
../src/basic/socket-util.c:1393:16: warning: ‘mtu’ may be used uninitialized in this function [-Wmaybe-uninitialized]
1393 | *ret = (size_t) mtu;
| ^~~~~~~~~~~~
As suggested in https://github.com/systemd/systemd/pull/11484#issuecomment-775288617.
This does not touch anything exposed in src/systemd. Changing the defines there
would be a compatibility break.
Note that tests are broken after this commit. They will be fixed in the next one.
A variety of sockopts exist both for IPv4 and IPv6 but require a
different pair of sockopt level/option number. Let's add helpers for
these that internally determine the right sockopt to call.
This should shorten code that generically wants to support both ipv4 +
ipv6 and for the first time adds correct support for some cases where we
only called the ipv4 versions, and not the ipv6 options.
We always need to make them unions with a "struct cmsghdr" in them, so
that things properly aligned. Otherwise we might end up at an unaligned
address and the counting goes all wrong, possibly making the kernel
refuse our buffers.
Also, let's make sure we initialize the control buffers to zero when
sending, but leave them uninitialized when reading.
Both the alignment and the initialization thing is mentioned in the
cmsg(3) man page.
In subsequent commits, calls to if_nametoindex() will be replaced by a wrapper
that falls back to alternative name resolution over netlink. netlink support
requires libsystemd (for sd-netlink), and we don't want to add any functions
that require netlink in basic/. So stuff that calls if_nametoindex() for user
supplied interface names, and everything that depends on that, needs to be
moved.
Michiel
Yu Watanabe
Mike Yuan
Lennart Poettering
Luca Boccassi
Zbigniew Jędrzejewski-Szmek
Luca Boccassi