nftables uses a transaction-based netlink model: one netlink write
comes with multiple messages.
A 'BEGIN' message to tell nf_tables/kernel that a new transaction starts.
Then, one more messages to add/delete tables/chains/rules etc.
Lastly, an END message that commits all changes.
This function will be used to send all the individual messages that should
make up a single transaction as a single write.
This also makes sure the control buffer is properly aligned. This
matters, as otherwise the control buffer might not be aligned and the
cmsg buffer counting might be off. The incorrect alignment is becoming
visible by using recvmsg_safe() as we suddenly notice the MSG_CTRUNC bit
set because of this.
That said, apparently this isn't enough to make this work on all
kernels. Since I couldn't figure this out, we now add 1K to the buffer
to be sure. We do this once already, also for a pktinfo structure
(though an IPv4/IPv6) one. I am puzzled by this, but this shouldn't
matter much. it works locally just fine, except for those ubuntu CI
kernels...
While we are at it, make some other changes too, to simplify and
modernize the function.
Same as with the other users, any non-trivial use of the objects requires
use from a single thread only or external locking. Using atomic operations
just for reference counts is not useful.
All over the place we define local variables for the various sockopts
that take a bool-like "int" value. Sometimes they are const, sometimes
static, sometimes both, sometimes neither.
Let's clean this up, introduce a common const variable "const_int_one"
(as well as one matching "const_int_zero") and use it everywhere, all
acorss the codebase.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
This adds some paranoia code that moves some of the fds we allocate for
longer periods of times to fds > 2 if they are allocated below this
boundary. This is a paranoid safety thing, in order to avoid that
external code might end up erroneously use our fds under the assumption
they were valid stdin/stdout/stderr. Think: some app closes
stdin/stdout/stderr and then invokes 'fprintf(stderr, …' which causes
writes on our fds.
This both adds the helper to do the moving as well as ports over a
number of users to this new logic. Since we don't want to litter all our
code with invocations of this I tried to strictly focus on fds we keep
open for long periods of times only and only in code that is frequently
loaded into foreign programs (under the assumptions that in our own
codebase we are smart enough to always keep stdin/stdout/stderr
allocated to avoid this pitfall). Specifically this means all code used
by NSS and our sd-xyz API:
1. our logging APIs
2. sd-event
3. sd-bus
4. sd-resolve
5. sd-netlink
This changed was inspired by this:
https://github.com/systemd/systemd/issues/8075#issuecomment-363689755
This shows that apparently IRL there are programs that do close
stdin/stdout/stderr, and we should accomodate for that.
Note that this won't fix any bugs, this just makes sure that buggy
programs are less likely to interfere with out own code.
This also adds the ability to incorporate arrays into netlink messages
and to determine when a netlink message is too big, used by some generic
netlink protocols.
If our netlink input buffer overruns the kernel will send us ENOBUFS on
the next recvmsg(). Don't consider this a complete failure resulting in
closing of the netlink socket. Instead, simply continue (after debug
logging).
Of course, ideally we'd have a better strategy for this, and would have
a way to resync if this happens (as well as a scheme for cancelling all
ongoing asynchronous transactions), but for now let's at least not choke
fatally, and simply accept that we lost some messages and continue.
Note that if we lose messages when synchronously waiting for an
operation to complete, we'll still propagate the ENOBUFS up, to make the
individual transaction fail.
See: #5398
(This bug does not properly fix the issue, hence we should leave the bug
open.)
We don't have plural in the name of any other -util files and this
inconsistency trips me up every time I try to type this file name
from memory. "formats-util" is even hard to pronounce.
Throughout the tree there's spurious use of spaces separating ++ and --
operators from their respective operands. Make ++ and -- operator
consistent with the majority of existing uses; discard the spaces.
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
There are more than enough calls doing string manipulations to deserve
its own files, hence do something about it.
This patch also sorts the #include blocks of all files that needed to be
updated, according to the sorting suggestions from CODING_STYLE. Since
pretty much every file needs our string manipulation functions this
effectively means that most files have sorted #include blocks now.
Also touches a few unrelated include files.
Track the number of matches installed for a given multicast group, and leave the
group once no matches depend on it.
In order to handle passed-in sockets that are already members of multicast groups
we initialize the refcount based on the membership once we take over the socket.
This way we will leave the socket in the state we found it once we finish with
it.
On kernels that do not fully support reading out the multicast group membership
we fall back to never leaving any groups (as before).
Explicitly export the root type-system to the type-system callers. This
avoids treating NULL as root, which for one really looks backwards (NULL
is usually a leaf, not root), and secondly prevents us from properly
debugging calling into non-nested types.
Also rename the root to "type_system_root". Once we support more than
rtnl, well will have to revisit that, anyway.
If we extend NLType to support arrays and further extended types, we
really want to avoid hard-coding the type-layout outside of
netlink-types.c. We already avoid accessing nl_type->type_system outside
of netlink-types.c, extend this to also avoid accessing any other fields.
Provide accessor functions for nl_type->type and nl_type->size and then
move NLType away from the type-system header.
With this in place, follow-up patches can safely turn "type_system" and
"type_system_union" into a real "union { }", and then add another type for
arrays.
Yu Watanabe