"shared/nm-utils" contains general purpose utility functions that only
depend on glib (and extend glib with some helper functions).
We will also add code that does not use glib, hence it would be good
if the part of "shared/nm-utils" that does not depend on glib, could be
used by these future projects.
Also, we use the term "utils" everywhere. While that covers the purpose
and content well, having everything called "nm-something-utils" is not
great. Instead, call this "nm-std-aux", inspired by "c-util/c-stdaux".
(cherry picked from commit b434b9ec07)
nla_get_u64() was unlike all other nla_get_u*() implementations, in that it
would allow for a missing/invalid nla argument, and return 0.
Don't do this. For one, don't behave different than other getters.
Also, there really is no space to report errors. Hence, the caller must
make sure that the attribute is present and suitable -- like for other
nla_get_*() functions.
None of the callers relied on being able to pass NULL attribute.
Also, inline the function and use unaligned_read_ne64(). That is our
preferred way for reading unaligned data, not memcpy().
These are only nm_assert(), meaning on non-DEBUG builds they
are not enabled.
Callers are supposed to first check that the netlink attribute
is suitable. Hence, we just assert.
- use size_t arguments for the memory sizes. While sizes from netlink
API currently are int typed and inherrently limited, use the more
appropriate data type.
- rename the arguments. The "count" is really the size of the
destination buffer.
- return how many bytes we wanted to write (like g_strlcpy()).
That makes more sense than how many bytes we actually wrote
because previously, we could not detect truncation.
Anyway, none of the callers cared about the return-value either
way.
The common idiom is to stack allocate the tb array. Hence,
the maxtype is redundant. Add macros that autodetect the
maxtype based on the C type infomation.
Also, there is a static assertion that the size of the policy
(if provided) matches.
Rename variables for the error number. Commonly the naming
is:
- errno: the error number from <errno.h> itself
- errsv: a copy of errno
- nlerr: a netlink error number
- err: an error code, but not a errno/errsv and not
a netlink error number.
(cherry picked from commit f4de941d98)
It's only used internally, and it seems not very useful to have.
As it is confusing to have multiple functions for doing something
similar, drop it -- since it's not really used. I also cannot imagine
a good use-case for it.
Kernel recently got support for exposing TUN/TAP information on netlink
[1], [2], [3]. Add support for it to the platform cache.
The advantage of using netlink is that querying sysctl bypasses the
order of events of the netlink socket. It is out of sync and racy. For
example, platform cache might still think that a tun device exists, but
a subsequent lookup at sysfs might fail because the device was deleted
in the meantime. Another point is, that we don't get change
notifications via sysctl and that it requires various extra syscalls
to read the device information. If the tun information is present on
netlink, put it into the cache. This bypasses checking sysctl while
we keep looking at sysctl for backward compatibility until we require
support from kernel.
Notes:
- we had two link types NM_LINK_TYPE_TAP and NM_LINK_TYPE_TUN. This
deviates from the model of how kernel treats TUN/TAP devices, which
makes it more complicated. The link type of a NMPlatformLink instance
should match what kernel thinks about the device. Point in case,
when parsing RTM_NETLINK messages, we very early need to determine
the link type (_linktype_get_type()). However, to determine the
type of a TUN/TAP at that point, we need to look into nested
netlink attributes which in turn depend on the type (IFLA_INFO_KIND
and IFLA_INFO_DATA), or even worse, we would need to look into
sysctl for older kernel vesions. Now, the TUN/TAP type is a property
of the link type NM_LINK_TYPE_TUN, instead of determining two
different link types.
- various parts of the API (both kernel's sysctl vs. netlink) and
NMDeviceTun vs. NMSettingTun disagree whether the PI is positive
(NM_SETTING_TUN_PI, IFLA_TUN_PI, NMPlatformLnkTun.pi) or inverted
(NM_DEVICE_TUN_NO_PI, IFF_NO_PI). There is no consistent way,
but prefer the positive form for internal API at NMPlatformLnkTun.pi.
- previously NMDeviceTun.mode could not change after initializing
the object. Allow for that to happen, because forcing some properties
that are reported by kernel to not change is wrong, in case they
might change. Of course, in practice kernel doesn't allow the device
to ever change its type, but the type property of the NMDeviceTun
should not make that assumption, because, if it actually changes, what
would it mean?
- note that as of now, new netlink API is not yet merged to mainline Linus
tree. Shortcut _parse_lnk_tun() to not accidentally use unstable API
for now.
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1277457
[2] https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=1ec010e705934c8acbe7dbf31afc81e60e3d828b
[3] https://git.kernel.org/pub/scm/network/iproute2/iproute2-next.git/commit/?id=118eda77d6602616bc523a17ee45171e879d1818https://bugzilla.redhat.com/show_bug.cgi?id=1547213https://github.com/NetworkManager/NetworkManager/pull/77
From v4.12 the kernel appends some attributes to netlink acks
containing a textual description of the error and other fields (see
commit [1]). Parse those attributes and print the error message.
Examples:
platform-linux: netlink: recvmsg: error message from kernel: Network is unreachable (101) "Nexthop has invalid gateway" for request 12
platform-linux: netlink: recvmsg: error message from kernel: Invalid argument (22) "Local address cannot be multicast" for request 21
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2d4bc93368f5a0ddb57c8c885cdad9c9b7a10ed5
Now that we cleaned up nl_recv(), we have full control over which error
variables are returned when. We no longer need to check "errno"
directly, and we no longer need the NLE_USER_* workaround.
Glib is not out of memory safe, meaning it always aborts the program
when an allocation fails. It is not possible to meaningfully handle
out of memory when using glib.
Replace all allocation functions for netlink message with their glib
counter part and remove the NULL checks.
With libnl3, each socket has it's own callback structure.
One would often take that callback structure, clone it, modify it
and invoke a receive operation with it.
We don't need this complexity. We got rid of all default handlers,
hence, by default all callbacks are unset.
The only callbacks that are set, are those that we specify immediately
before invoking the receive operation. Just pass the callback structure
at that point.
Also, no more ref-counting, and cloning of the callback structure. It is
so simple, just stack allocate one if you need it.
The only difference between nl_recvmsgs_report() and nl_recvmsgs() is
the return value on success. libnl3 couldn't change that for backward
compatibility reasons. We can merge them.
Originally, these were error numbers from libnl3. These error numbers
are separate from errno, which is unfortunate, because sometimes we
care about the native errno returned from kernel.
Now, refactor them so that the error numbers are in the shared realm
of errno, but failures from kernel or underlying API are still returned
via their native errno.
- NLE_INVAL doesn't exist anymore. Passing invalid arguments to a function
is commonly a bug. g_return_*(NLE_BUG) is the right answer to that.
- NLE_NOMEM and NLE_AGAIN is replaced by their errno counterparts.
- drop several error numbers. If nobody cares about these numbers,
there is no reason to have a specific error number for them.
NLE_UNSPEC is sufficient.
From libnl3, we only used the helper function to parse/generate netlink
messages and the socket functions to send/receive messages. We don't
need an external dependency to do that, it is simple enough.
Drop the libnl3 dependency, and replace all missing code by directly
copying it from libnl3 sources. At this point, I mostly tried to
import the required bits to make it working with few modifications.
Note that this increases the binary size of NetworkManager by 4736 bytes
for contrib/rpm build on x86_64. In the future, we can simplify the code
further.
A few modifications from libnl3 are:
- netlink errors NLE_* are now in the domain or regular errno.
The distinction of having to bother with two kinds of error
number domains was annoying.
- parts of the callback handling is copied partially and unused parts
are dropped. Especially, the verbose/debug handlers are not used.
In following commits, the callback handling will be significantly
simplified.
- the complex handling of seleting ports was simplified. We now always
let kernel choose the right port automatically.
Especially useful, because we don't link against libnl-genl-3.so
but re-implement generic netlink support. Such code should go there
so it can be used by various components.
