Handling these events notifies hwsim of address changes for interface
creation/removal outside the initial namespace as well as address
changes due to scanning address randomization.
Interfaces that hwsim already knows about are still handled via
nl80211. But any interfaces not known when ADD/DEL_MAC_ADDR events
come will be treated specially.
For ADD, a dummy interface object will be created and added to the
queue. This lets the frame processing match the destination address
correctly. This can happen both for scan randomization and interface
creation outside of the initial namespace.
For the DEL event we handle similarly and don't touch any interfaces
found via nl80211 (i.e. have a 'name') but need to also be careful
with the dummy interfaces that were created outside the initial
namespace. We want to keep these around but scanning MAC changes can
also delete them. This is why a reference count was added so scanning
doesn't cause a removal.
For example, the following sequence:
ADD_MAC_ADDR (interface creation)
ADD_MAC_ADDR (scanning started)
DEL_MAC_ADDR (scanning done)
After adding prefix matching the rule structure contained allocated
memory which was not being cleaned up on exit if rules still
remained in the list (removing the rule via DBus was done correctly)
If a rule was disabled it would cause hwsim to not continue processing
frames using rules further in the queue. _Most_ tests only use one
rule so this shouldn't have changed their behavior but others which
use multiple rules may be effected and the tests have not been
running properly.
Currently CreateRadio only allows a single outstanding DBus message
until the radio is fully created. 99% of the time this is just fine
but in order to test dual phy cards there needs to be support for
phy's appearing at the same time.
This required storing the pending DBus message inside the radio object
rather than a single static variable.
The code was refactored to handle the internal radio info objects better
for the various cases:
- Creation from CreateRadio()
- Radio already existed before hwsim started, or created externally
- Existing radio changed name, address, etc.
First, Name is now a required option to CreateRadio(). This allows
the radio info to be pushed to the queue immediately (also allowing the
pending DBus message to be tracked). Then, when the NEW_RADIO event
fires the pending radio can be looked up (by name) and filled with the
remaining info.
If the radio was not found by name but a matching ID was found this is
the 'changed' case and the radio is re-initialized with the changed
values.
If neither name or ID matches the radio was created externally, or
prior to hwsim starting. A radio info object is created at this time
and initialized.
The ID was changed to a signed integer in order to initialize it to an
invalid number -1. Doing this was required since a pending uninitalized
radio ID (0) could match an existing radio ID. This required some
bounds checks in case the kernels counter reaches an extremely high value.
This isn't likely to ever happen in practice.
Right now hwsim blindly tries to forward broadcast/multicast frames to
all interfaces it knows about and relies on the kernel to reject the
forwarding attempt if the frequency does not match. This results in
multiple copies of the same message being added to the genl transmit
queue.
On slower systems this can cause a run-away memory consumption effect
where the queued messages are not processed in time prior to a new
message being received for forwarding. The likelyhood of this effect
manifesting itself is directly related to the number of hostapd
instances that are created and are beaconing simultaneously.
Try to optimize frame forwarding by not sending beacon frames
to those interfaces that are in AP mode (i.e. pure hostapd instances)
since such interfaces are going to be operating on a different frequency
and would not be interested in processing beacon frames anyway.
This optimization cuts down peak memory use during certain tests by 30x
or more (~33mb to ~1mb) when profiled with 'valgrind --tool=massif'
If set, a rule will start matching 'MatchBytes' some number of bytes
into the frame (MatchBytesOffset). This is useful since header
information, addresses, and sequence numbers may be unpredictable
between test runs.
To avoid unintended matches the Prefix property is left unchanged
and will match starting at the beginning of the frame.
The hwsim rules did not treat frames and ACKs any differently which
can mislead the developer especially when setting a rule prefix.
If a prefix was used the frame ACK was actually being matched against
the original frame payload which seems wrong because the ACK is not
the original frame.
Though strange, matching the frame prefix on an ACK has its place if
the developer wants to block just the ACK rather than the frame so
to make this case more clear 'DropAck' was added as a rule property.
And only if this is true will an ACK be checked and potentially
dropped.
To maintain the current hwsim behavior DropAck will default to true.
This integer property can be set to only match a rule a number of
times rather than all packets. This is useful for testing behavior
of a single dropped frame or ack. Once the rule has been matched
'MatchTimes' the rules will no longer be applied (unless set again
to some integer greater than zero).
This was initially put in to solve an issue that was specific to
mac80211_hwsim where the connect callback would get queued and
delayed until after the connect event. This caused IWD to get very
confused.
Later it was found that "real" drivers can sometimes do this so
some code was added to IWD core to handle it.
Now there isn't much point to delay all frames unless a rule specifies
so change the behavior back to sending out frames immediately.
The hwsim Rule API was structured as properties so once a rule is
created it automatically starts being applied to frames. This happens
before anything has time to actually define the rule (source, destination
etc). This leads to every single frame being matched to the rule until
these other properties are added, which can result in unexpected behavior.
To fix this an "Enabled" property has been added and the rule will not
be applied until this is true.
The Create() API was limited to only taking a Name and boolean
(for p2p enabling). The actual hwsim nl80211 API can take more
attributes than this (which are actually utilized when creating
from the command line). To get the DBus API up to the same
functionality the two arguments in Create were replaced with
a single dictionary. This allows for extending later if more
arguments are needed.
In the NEW_RADIO callback hwsim was assuming that DBus had no
yet replied to the Create() method. In some cases the NEW_RADIO
event fires before the actual callback which will respond to
DBus. This causes a crash in the create callback.
Starts hwsim but does not register to mac80211_hwsim. This is to
allow autotests to disable hwsim, while still having the ability
to create/destroy radios over DBus.
Besides being undefined behaviour, signed integer overflow can cause
unexpected comparison results. In the case of network_rank_compare(),
a connected network with rank INT_MAX would cause newly inserted
networks with negative rank to be inserted earlier in the ordered
network list. This is reflected in the GetOrderedMethods() DBus method
as can be seen in the following iwctl output:
[iwd]# station wlan0 get-networks
Network name Security Signal
----------------------------------------------------
BEOLAN 8021x **** }
BeoBlue psk *** } all unknown,
UI_Test_Network psk *** } hence assigned
deneb_2G psk *** } negative rank
BEOGUEST open **** }
> titan psk ****
Linksys05274_5GHz_dmt psk ****
Lyngby-4G-4 5GHz psk ****
Using mac80211_hwsim can sometimes result in out of order messages
coming from the kernel. Since mac80211_hwsim immediately sends out
frames and the kernel keeps command responses in a separate queue,
bad scheduling can result in these messages being out of order.
In some cases we receive Auth/Assoc frames before the response to
our original CMD_CONNECT. This causes autotests to fail randomly,
some more often than others.
To fix this we can introduce a small delay into hwsim. Just a 1ms
delay makes the random failures disappear in the tests. This delay
is also makes hwsim more realistic since actual hardware will always
introduce some kind of delay when sending or receiving frames.
mac80211_hwsim now allows setting supported iftypes/ciphers. This patch
enables this support in hwsim. Specific iftypes/ciphers can now be
disabled via the command line when creating a radio:
Disable iftypes:
--iftype-disable station,ap,adhoc,p2p_client,p2p_go,mesh_point
Disable cipher types:
--cipher-disable ccmp,tkip,wep
Since we don't catch all hwsim attribute types in unicast_handler
you see tons of "Unknown attribute type: X" prints. Since this is
not an error, we should only print if the attribute does not exist
in the attribute list.
In mac80211_hwsim each radio is assigned two addresses, the second (addr
1) being used over nl80211. In SendFrame we'd hardcode the mapping of
address 0 to address 1 even though we track all the addresses in radio_info,
so instead use that data to find the radio that has given address 0. Also
if no address 0 matches what was supplied over DBus try to find a matching
address 1.
There are ways userspace can request different addresses when managing
mac80211_hwsim radios and the hardcoded mapping would become wrong.
James Prestwood