According to the specification[1] the 'capabilities' describe the physical
device as a whole and the 'device_caps' describe the current device node.
The existence of 'device_caps' is indicated by the V4L2_CAP_DEVICE_CAPS
capability flag.
Use the 'device_caps' if available to generate the correct
ID_V4L_CAPABILITIES for the current device node.
This is relevant for UVC devices with current kernels: Two /dev/videoX
devices exist for those. One for video and one for metadata. The
V4L2_CAP_VIDEO_CAPTURE flag is present in the 'capabilities' for both
device nodes but only in the 'device_caps' of the video device node.
Without this, the ID_V4L_CAPABILITIES of the metadata device node
incorrectly contains 'capture'.
[1] https://www.linuxtv.org/downloads/v4l-dvb-apis-new/uapi/v4l/vidioc-querycap.html
Originally commented as "devices names might have changed/swapped in the meantime",
but may not. For safety, let's block the following events with same
devpath.
This may fix#6514.
Fixes#3374. The problem is that we set MACPolicy=persistent (i.e. we would
like to generate persistent MAC addresses for interfaces which don't have a
fixed MAC address), but various virtual interfaces including bridges, tun/tap,
bonds, etc., do not not have the necessary ID_NET_NAME_* attributes and udev
would not assing the address and warn:
Could not generate persistent MAC address for $name: No such file or directory
Basic requirements which I think a solution for this needs to satisfy:
1. No changes to MAC address generation for those cases which are currently
handled successfully. This means that net_get_unique_predictable_data() must
keep returning the same answer, which in turn means net_get_name() must keep
returning the same answer. We can only add more things we look at with lower
priority so that we start to cover cases which were not covered before.
2. Like 1, but for IPvLL seed and DHCP IAD. This is less important, but "nice
to have".
3. Keep MACPolicy=persistent. If people don't want it, they can always apply
local configuration, but in general stable MACs are a good thing. I have never
seen anyone complain about that.
== Various approaches that have been proposed
=== https://github.com/systemd/systemd/issues/3374#issuecomment-223753264 (tomty89)
if !ID_BUS and INTERFACE, use INTERFACE
I think this almost does the good thing, but I don't see the reason to reject ID_BUS
(i.e. physical hardware). Stable MACs are very useful for physical hardware that has
no physical MAC.
=== https://github.com/systemd/systemd/issues/3374#issuecomment-224733069 (teg)
if (should_rename(device, true))
This means looking at name_assign_type. In particular for
NET_NAME_USER should_rename(..., true) returns true. It only returns false
for NET_NAME_PREDICTABLE. So this would cover stuff like br0, bond0, etc,
but would not cover lo and other devices with predictable names. That doesn't
make much sense.
But did teg mean should_rename() or !should_rename()?
=== https://github.com/systemd/systemd/issues/3374#issuecomment-234628502 (tomty89):
+ if (!should_rename(device, true))
+ return udev_device_get_sysname(device)
This covers only devices with NET_NAME_PREDICTABLE. Since the problem applies as
much to bridges and such, this isn't neough.
=== https://github.com/systemd/systemd/issues/3374#issuecomment-281745967 (grafi-tt)
+ /* if the machine doesn't provide data about the device, use the ifname specified by userspace
+ * (this is the case when the device is virtual, e.g., bridge or bond) */
+ s = udev_device_get_sysattr_value(device, "name_assign_type");
+ if (s && safe_atou(s, &type) >= 0 && type == NET_NAME_USER)
+ return udev_device_get_sysname(device);
This does not cover bond0, vnet0, tun/tap and similar.
grafi-tt also proposes patching the kernel, but *not* setting name_assign_type
seems intentional in those cases, because the device name is a result of
enumeration, not set by the userspace.
=== https://github.com/systemd/systemd/issues/3374#issuecomment-288882355 (tomty89)
(also PR #11372)
- MACAddressPolicy=persistent
This break requirement 3. above. It would solve the immediate problem, but I
think the disruption is too big.
=== This patch
This patch means that we will set a "stable" MAC for pretty much any virtual
device by default, where "stable" means keyed off the machine-id and interface
name.
It seems like a big change, but we already did this for most physical devices.
Doing it also for virtual devices doesn't seem like a big issue. It will make
the setup and monitoring of virtualized networks slightly nicer. I don't think
anyone is depending on having the MAC address changed when those devices are
destoryed and recreated. If they do, they'd have to change MACAddressPolicy=.
== Implementation
net_get_name() is called from dhcp_ident_set_iaid() so I didn't change
net_get_name() like in grafi-tt's patch, but net_get_unique_predictable_data().
net_get_unique_predictable_data() is called from get_mac() in link-config.c
and sd_ipv4ll_set_address_seed(), so both of those code paths are affected
and will now get data in some cases where they errored out previously.
The return code is changed to -ENODATA since that gives a nicer error string.
If "keep" policy is specified, and the interface has a name that is
NET_NAME_USER or NET_NAME_RENAMED, we stop processing rules. "keep" should
probably be specified either first or last depending on the preference.
This partially reimplements 55b6530baa, in the
sense that if the "keep" policy is not specified, and if the interface has
a NamingPolicy, it will be renamed, even if it had a name previously.
So this breaks backwards compatibility in this case, but that's more in line
with what users expect.
Closes#9006.
What policy we dicide to use it rather important, but this bit of information
wasn't logged. Let's always do that.
The code was also written in a confusing way, which probably contributed to the
unintended effects of 55b6530baa and other commits.
We would loop over all policies, and note if "kernel" was specified, and then
possibly unset the result at the end. Let's immediately log the result and cut
to the end if we can figure out the answer.
No functional change intended, except for the new log lines.
Using goto is not very elegant, but we can't use break because of the switch,
and there are multiple conditions to break the loop, so using goto is cleanest.
This reverts commit 55b6530baa.
This commit description says "Always rename an interface to its name specified
in config if no NamePolicy= is specified", but it does much more:
1. It completely changes the meaning of NamePolicy=kernel. Before, it meant that an interface
with type==NAMEPOLICY_KERNEL would not be renamed. After, the kernel name only works as
a fallback, if no policy matches.
2. The "if no NamePolicy= is specified" part is not true at all, the interface will be renamed
according to the specified NamePolicy=.
After 55b6530baa, the should_rename() function is named very misleadingly: it is only used
to mean "respect kernel predictable name if no naming policy matches".
Let's revert, and start with a clean slate. This fixes#11436.
Before:
IMPORT builtin 'hwdb' fails: No such file or directory
After:
IMPORT builtin 'hwdb' fails: No data available
Previous log is confusing and may be understood as hwdb file not exist.
Now, not a few udevd debug logs come from sd-device or sd-hwdb.
Only setting LOG_REALM_UDEV may not sufficient to debug.
We have already similar code in main() and udevadm.
Found by inspecting results of running this small program:
int main(int argc, const char **argv) {
for (int i = 1; i < argc; i++) {
FILE *f;
char line[1024], prev[1024], *r;
int lineno;
prev[0] = '\0';
lineno = 1;
f = fopen(argv[i], "r");
if (!f)
exit(1);
do {
r = fgets(line, sizeof(line), f);
if (!r)
break;
if (strcmp(line, prev) == 0)
printf("%s:%d: error: dup %s", argv[i], lineno, line);
lineno++;
strcpy(prev, line);
} while (!feof(f));
fclose(f);
}
}
