Somehow we missed this for a long time, but similar to the extended
NSS support in VHT capabilities, we need to have this in Operating
Mode notification.
Implement it by
* parsing the 160/80+80 bit there and setting the bandwidth
appropriately
* having callers of ieee80211_get_vht_max_nss() pass in the current
max NSS value as received in the operating mode notification in
order to modify it appropriately depending on the extended NSS
bits.
This updates all drivers that use it, i.e. only iwlwifi/mvm.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20200326150855.098483728cfa.I4e8c25d3288441759c2793247197229f0696a37d@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Convert a user space registration for processing multicast Action frames
(NL80211_CMD_REGISTER_FRAME with NL80211_ATTR_RECEIVE_MULTICAST) to a
new enum ieee80211_filter_flags bit FIF_MCAST_ACTION so that drivers can
update their RX filter parameters appropriately, if needed.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200421144815.19175-1-jouni@codeaurora.org
[rename variables to rx_mcast_action_reg indicating action frames only]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Almost all drivers below cfg80211 get the API wrong (except for
cfg80211) and are unable to cope with multiple registrations for
the same frame type, which is valid due to the match filter.
This seems to indicate the API is wrong, and we should maintain
the full information in cfg80211 instead of the drivers.
Change the API to no longer inform the driver about individual
registrations and unregistrations, but rather every time about
the entire state of the entire wiphy and single wdev, whenever
it may have changed. This also simplifies the code in cfg80211
as it no longer has to track exactly what was unregistered and
can free things immediately.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Reviewed-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Link: https://lore.kernel.org/r/20200417124300.f47f3828afc8.I7f81ef59c2c5a340d7075fb3c6d0e08e8aeffe07@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Extend cfg80211_rx_unprot_mlme_mgmt() to cover indication of unprotected
Beacon frames in addition to the previously used Deauthentication and
Disassociation frames. The Beacon frame case is quite similar, but has
couple of exceptions: this is used both with fully unprotected and also
incorrectly protected frames and there is a rate limit on the events to
avoid unnecessary flooding netlink events in case something goes wrong.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Link: https://lore.kernel.org/r/20200401142548.6990-1-jouni@codeaurora.org
[add missing kernel-doc]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Don't allow user to create meter unlimitedly, which may cause
to consume a large amount of kernel memory. The max number
supported is decided by physical memory and 20K meters as default.
Cc: Pravin B Shelar <pshelar@ovn.org>
Cc: Andy Zhou <azhou@ovn.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
In kernel datapath of Open vSwitch, there are only 1024
buckets of meter in one datapath. If installing more than
1024 (e.g. 8192) meters, it may lead to the performance drop.
But in some case, for example, Open vSwitch used as edge
gateway, there should be 20K at least, where meters used for
IP address bandwidth limitation.
[Open vSwitch userspace datapath has this issue too.]
For more scalable meter, this patch use meter array instead of
hash tables, and expand/shrink the array when necessary. So we
can install more meters than before in the datapath.
Introducing the struct *dp_meter_instance, it's easy to
expand meter though changing the *ti point in the struct
*dp_meter_table.
Cc: Pravin B Shelar <pshelar@ovn.org>
Cc: Andy Zhou <azhou@ovn.org>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
x25_lapb_receive_frame() invokes x25_get_neigh(), which returns a
reference of the specified x25_neigh object to "nb" with increased
refcnt.
When x25_lapb_receive_frame() returns, local variable "nb" becomes
invalid, so the refcount should be decreased to keep refcount balanced.
The reference counting issue happens in one path of
x25_lapb_receive_frame(). When pskb_may_pull() returns false, the
function forgets to decrease the refcnt increased by x25_get_neigh(),
causing a refcnt leak.
Fix this issue by calling x25_neigh_put() when pskb_may_pull() returns
false.
Fixes: cb101ed2c3 ("x25: Handle undersized/fragmented skbs")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Normal there should be checked for nla_put_in6_addr like other
usage in net.
Detected by CoverityScan, CID# 1461639
Fixes: 01cacb00b3 ("mptcp: add netlink-based PM")
Signed-off-by: Bo YU <tsu.yubo@gmail.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
gro_flush_timeout and napi_defer_hard_irqs can be read
from napi_complete_done() while other cpus write the value,
whithout explicit synchronization.
Use READ_ONCE()/WRITE_ONCE() to annotate the races.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Back in commit 3b47d30396 ("net: gro: add a per device gro flush timer")
we added the ability to arm one high resolution timer, that we used
to keep not-complete packets in GRO engine a bit longer, hoping that further
frames might be added to them.
Since then, we added the napi_complete_done() interface, and commit
364b605573 ("net: busy-poll: return busypolling status to drivers")
allowed drivers to avoid re-arming NIC interrupts if we made a promise
that their NAPI poll() handler would be called in the near future.
This infrastructure can be leveraged, thanks to a new device parameter,
which allows to arm the napi hrtimer, instead of re-arming the device
hard IRQ.
We have noticed that on some servers with 32 RX queues or more, the chit-chat
between the NIC and the host caused by IRQ delivery and re-arming could hurt
throughput by ~20% on 100Gbit NIC.
In contrast, hrtimers are using local (percpu) resources and might have lower
cost.
The new tunable, named napi_defer_hard_irqs, is placed in the same hierarchy
than gro_flush_timeout (/sys/class/net/ethX/)
By default, both gro_flush_timeout and napi_defer_hard_irqs are zero.
This patch does not change the prior behavior of gro_flush_timeout
if used alone : NIC hard irqs should be rearmed as before.
One concrete usage can be :
echo 20000 >/sys/class/net/eth1/gro_flush_timeout
echo 10 >/sys/class/net/eth1/napi_defer_hard_irqs
If at least one packet is retired, then we will reset napi counter
to 10 (napi_defer_hard_irqs), ensuring at least 10 periodic scans
of the queue.
On busy queues, this should avoid NIC hard IRQ, while before this patch IRQ
avoidance was only possible if napi->poll() was exhausting its budget
and not call napi_complete_done().
This feature also can be used to work around some non-optimal NIC irq
coalescing strategies.
Having the ability to insert XX usec delays between each napi->poll()
can increase cache efficiency, since we increase batch sizes.
It also keeps serving cpus not idle too long, reducing tail latencies.
Co-developed-by: Luigi Rizzo <lrizzo@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
gro_cells lib is used by different encapsulating netdevices, such as
geneve, macsec, vxlan etc. to speed up decapsulated traffic processing.
CPU tag is a sort of "encapsulation", and we can use the same mechs to
greatly improve overall DSA performance.
skbs are passed to the GRO layer after removing CPU tags, so we don't
need any new packet offload types as it was firstly proposed by me in
the first GRO-over-DSA variant [1].
The size of struct gro_cells is sizeof(void *), so hot struct
dsa_slave_priv becomes only 4/8 bytes bigger, and all critical fields
remain in one 32-byte cacheline.
The other positive side effect is that drivers for network devices
that can be shipped as CPU ports of DSA-driven switches can now use
napi_gro_frags() to pass skbs to kernel. Packets built that way are
completely non-linear and are likely being dropped without GRO.
This was tested on to-be-mainlined-soon Ethernet driver that uses
napi_gro_frags(), and the overall performance was on par with the
variant from [1], sometimes even better due to minimal overhead.
net.core.gro_normal_batch tuning may help to push it to the limit
on particular setups and platforms.
iperf3 IPoE VLAN NAT TCP forwarding (port1.218 -> port0) setup
on 1.2 GHz MIPS board:
5.7-rc2 baseline:
[ID] Interval Transfer Bitrate Retr
[ 5] 0.00-120.01 sec 9.00 GBytes 644 Mbits/sec 413 sender
[ 5] 0.00-120.00 sec 8.99 GBytes 644 Mbits/sec receiver
Iface RX packets TX packets
eth0 7097731 7097702
port0 426050 6671829
port1 6671681 425862
port1.218 6671677 425851
With this patch:
[ID] Interval Transfer Bitrate Retr
[ 5] 0.00-120.01 sec 12.2 GBytes 870 Mbits/sec 122 sender
[ 5] 0.00-120.00 sec 12.2 GBytes 870 Mbits/sec receiver
Iface RX packets TX packets
eth0 9474792 9474777
port0 455200 353288
port1 9019592 455035
port1.218 353144 455024
v2:
- Add some performance examples in the commit message;
- No functional changes.
[1] https://lore.kernel.org/netdev/20191230143028.27313-1-alobakin@dlink.ru/
Signed-off-by: Alexander Lobakin <bloodyreaper@yandex.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
RFC4862 5.5.3 e) prevents received Router Advertisements from reducing
the Valid Lifetime of configured addresses to less than two hours, thus
preventing hosts from reacting to the information provided by a router
that has positive knowledge that a prefix has become invalid.
This patch makes hosts honor all Valid Lifetime values, as per
draft-gont-6man-slaac-renum-06, Section 4.2. This is meant to help
mitigate the problem discussed in draft-ietf-v6ops-slaac-renum.
Note: Attacks aiming at disabling an advertised prefix via a Valid
Lifetime of 0 are not really more harmful than other attacks
that can be performed via forged RA messages, such as those
aiming at completely disabling a next-hop router via an RA that
advertises a Router Lifetime of 0, or performing a Denial of
Service (DoS) attack by advertising illegitimate prefixes via
forged PIOs. In scenarios where RA-based attacks are of concern,
proper mitigations such as RA-Guard [RFC6105] [RFC7113] should
be implemented.
Signed-off-by: Fernando Gont <fgont@si6networks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull nfsd fixes from Chuck Lever:
"The first set of 5.7-rc fixes for NFS server issues.
These were all unresolved at the time the 5.7 window opened, and
needed some additional time to ensure they were correctly addressed.
They are ready now.
At the moment I know of one more urgent issue regarding the NFS
server. A fix has been tested and is under review. I expect to send
one more pull request, containing this fix (which now consists of 3
patches).
Fixes:
- Address several use-after-free and memory leak bugs
- Prevent a backchannel livelock"
* tag 'nfsd-5.7-rc-1' of git://git.linux-nfs.org/projects/cel/cel-2.6:
svcrdma: Fix leak of svc_rdma_recv_ctxt objects
svcrdma: Fix trace point use-after-free race
SUNRPC: Fix backchannel RPC soft lockups
SUNRPC/cache: Fix unsafe traverse caused double-free in cache_purge
nfsd: memory corruption in nfsd4_lock()
In Commit dd9ee34440 ("vti4: Fix a ipip packet processing bug in
'IPCOMP' virtual tunnel"), it tries to receive IPIP packets in vti
by calling xfrm_input(). This case happens when a small packet or
frag sent by peer is too small to get compressed.
However, xfrm_input() will still get to the IPCOMP path where skb
sec_path is set, but never dropped while it should have been done
in vti_ipcomp4_protocol.cb_handler(vti_rcv_cb), as it's not an
ipcomp4 packet. This will cause that the packet can never pass
xfrm4_policy_check() in the upper protocol rcv functions.
So this patch is to call ip_tunnel_rcv() to process IPIP packets
instead.
Fixes: dd9ee34440 ("vti4: Fix a ipip packet processing bug in 'IPCOMP' virtual tunnel")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
The data fin flag is set only via a DSS option, but
mptcp_incoming_options() copies it unconditionally from the
provided RX options.
Since we do not clear all the mptcp sock RX options in a
socket free/alloc cycle, we can end-up with a stray data_fin
value while parsing e.g. MPC packets.
That would lead to mapping data corruption and will trigger
a few WARN_ON() in the RX path.
Instead of adding a costly memset(), fetch the data_fin flag
only for DSS packets - when we always explicitly initialize
such bit at option parsing time.
Fixes: 648ef4b886 ("mptcp: Implement MPTCP receive path")
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix the following coccicheck warning:
net/caif/caif_dev.c:410:2-13: WARNING: Assignment of 0/1 to bool
variable
net/caif/caif_dev.c:445:2-13: WARNING: Assignment of 0/1 to bool
variable
net/caif/caif_dev.c:145:1-12: WARNING: Assignment of 0/1 to bool
variable
net/caif/caif_dev.c:223:1-12: WARNING: Assignment of 0/1 to bool
variable
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When starting shutdown in sctp_sf_do_dupcook_a(), get the value for
SHUTDOWN Cumulative TSN Ack from the new association, which is
reconstructed from the cookie, instead of the old association, which
the peer doesn't have anymore.
Otherwise the SHUTDOWN is either ignored or replied to with an ABORT
by the peer because CTSN Ack doesn't match the peer's Initial TSN.
Fixes: bdf6fa52f0 ("sctp: handle association restarts when the socket is closed.")
Signed-off-by: Jere Leppänen <jere.leppanen@nokia.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When we start shutdown in sctp_sf_do_dupcook_a(), we want to bundle
the SHUTDOWN with the COOKIE-ACK to ensure that the peer receives them
at the same time and in the correct order. This bundling was broken by
commit 4ff40b8626 ("sctp: set chunk transport correctly when it's a
new asoc"), which assigns a transport for the COOKIE-ACK, but not for
the SHUTDOWN.
Fix this by passing a reference to the COOKIE-ACK chunk as an argument
to sctp_sf_do_9_2_start_shutdown() and onward to
sctp_make_shutdown(). This way the SHUTDOWN chunk is assigned the same
transport as the COOKIE-ACK chunk, which allows them to be bundled.
In sctp_sf_do_9_2_start_shutdown(), the void *arg parameter was
previously unused. Now that we're taking it into use, it must be a
valid pointer to a chunk, or NULL. There is only one call site where
it's not, in sctp_sf_autoclose_timer_expire(). Fix that too.
Fixes: 4ff40b8626 ("sctp: set chunk transport correctly when it's a new asoc")
Signed-off-by: Jere Leppänen <jere.leppanen@nokia.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There is no reason to fail the probing of the switch if the MTU couldn't
be configured correctly (either the switch port itself, or the host
port) for whatever reason. MTU-sized traffic probably won't work, sure,
but we can still probably limp on and support some form of communication
anyway, which the users would probably appreciate more.
Fixes: bfcb813203 ("net: dsa: configure the MTU for switch ports")
Reported-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add tracepoint support for QRTR with NS as the first candidate. Later on
this can be extended to core QRTR and transport drivers.
The trace_printk() used in NS has been replaced by tracepoints.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv6/ila/ila_xlat.c:604:0: warning: macro "ILA_HASH_TABLE_SIZE" is not used [-Wunused-macros]
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
When the act_ct SW offload in flowtable, The counter of the conntrack
entry will never update. So update the nf_conn_acct conuter in act_ct
flowtable software offload.
Signed-off-by: wenxu <wenxu@ucloud.cn>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
IPSKB_XFRM_TRANSFORMED and IP6SKB_XFRM_TRANSFORMED are skb flags set by
xfrm code to tell other skb handlers that the packet has been passed
through the xfrm output functions. Simplify the code and just always
set them rather than conditionally based on netfilter enabled thus
making the flag available for other users.
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
rpc_clnt_test_and_add_xprt() invokes rpc_call_null_helper(), which
return the value of rpc_run_task() to "task". Since rpc_run_task() is
impossible to return an ERR pointer, there is no need to add the
IS_ERR() condition on "task" here. So we need to remove it.
Fixes: 7f55489058 ("SUNRPC: Allow addition of new transports to a struct rpc_clnt")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Commit 018d26fcd1 ("cgroup, netclassid: periodically release file_lock
on classid") added a second cond_resched to write_classid indirectly by
update_classid_task. Remove the one in write_classid.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Yakunin <zeil@yandex-team.ru>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Get rid of linux/vermagic.h includes, so that MODULE_ARCH_VERMAGIC from
the arch header arch/x86/include/asm/module.h won't be redefined.
In file included from ./include/linux/module.h:30,
from drivers/net/ethernet/3com/3c515.c:56:
./arch/x86/include/asm/module.h:73: warning: "MODULE_ARCH_VERMAGIC"
redefined
73 | # define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY
|
In file included from drivers/net/ethernet/3com/3c515.c:25:
./include/linux/vermagic.h:28: note: this is the location of the
previous definition
28 | #define MODULE_ARCH_VERMAGIC ""
|
Fixes: 6bba2e89a8 ("net/3com: Delete driver and module versions from 3com drivers")
Co-developed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Shannon Nelson <snelson@pensando.io> # ionic
Acked-by: Sebastian Reichel <sre@kernel.org> # power
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pablo Neira Ayuso says:
====================
Netfilter fixes for net
The following patchset contains Netfilter fixes for net:
1) flow_block_cb memleak in nf_flow_table_offload_del_cb(), from Roi Dayan.
2) Fix error path handling in nf_nat_inet_register_fn(), from Hillf Danton.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
batadv_v_ogm_process() invokes batadv_hardif_neigh_get(), which returns
a reference of the neighbor object to "hardif_neigh" with increased
refcount.
When batadv_v_ogm_process() returns, "hardif_neigh" becomes invalid, so
the refcount should be decreased to keep refcount balanced.
The reference counting issue happens in one exception handling paths of
batadv_v_ogm_process(). When batadv_v_ogm_orig_get() fails to get the
orig node and returns NULL, the refcnt increased by
batadv_hardif_neigh_get() is not decreased, causing a refcnt leak.
Fix this issue by jumping to "out" label when batadv_v_ogm_orig_get()
fails to get the orig node.
Fixes: 9323158ef9 ("batman-adv: OGMv2 - implement originators logic")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
batadv_show_throughput_override() invokes batadv_hardif_get_by_netdev(),
which gets a batadv_hard_iface object from net_dev with increased refcnt
and its reference is assigned to a local pointer 'hard_iface'.
When batadv_store_throughput_override() returns, "hard_iface" becomes
invalid, so the refcount should be decreased to keep refcount balanced.
The issue happens in one error path of
batadv_store_throughput_override(). When batadv_parse_throughput()
returns NULL, the refcnt increased by batadv_hardif_get_by_netdev() is
not decreased, causing a refcnt leak.
Fix this issue by jumping to "out" label when batadv_parse_throughput()
returns NULL.
Fixes: 0b5ecc6811 ("batman-adv: add throughput override attribute to hard_ifaces")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
batadv_show_throughput_override() invokes batadv_hardif_get_by_netdev(),
which gets a batadv_hard_iface object from net_dev with increased refcnt
and its reference is assigned to a local pointer 'hard_iface'.
When batadv_show_throughput_override() returns, "hard_iface" becomes
invalid, so the refcount should be decreased to keep refcount balanced.
The issue happens in the normal path of
batadv_show_throughput_override(), which forgets to decrease the refcnt
increased by batadv_hardif_get_by_netdev() before the function returns,
causing a refcnt leak.
Fix this issue by calling batadv_hardif_put() before the
batadv_show_throughput_override() returns in the normal path.
Fixes: 0b5ecc6811 ("batman-adv: add throughput override attribute to hard_ifaces")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
and change to pseudorandom numbers, as this is a traffic dithering
operation that doesn't need crypto-grade.
The previous code operated in 4 steps:
1. Generate a random byte 0 <= rand_tq <= 255
2. Multiply it by BATADV_TQ_MAX_VALUE - tq
3. Divide by 255 (= BATADV_TQ_MAX_VALUE)
4. Return BATADV_TQ_MAX_VALUE - rand_tq
This would apperar to scale (BATADV_TQ_MAX_VALUE - tq) by a random
value between 0/255 and 255/255.
But! The intermediate value between steps 3 and 4 is stored in a u8
variable. So it's truncated, and most of the time, is less than 255, after
which the division produces 0. Specifically, if tq is odd, the product is
always even, and can never be 255. If tq is even, there's exactly one
random byte value that will produce a product byte of 255.
Thus, the return value is 255 (511/512 of the time) or 254 (1/512
of the time).
If we assume that the truncation is a bug, and the code is meant to scale
the input, a simpler way of looking at it is that it's returning a random
value between tq and BATADV_TQ_MAX_VALUE, inclusive.
Well, we have an optimized function for doing just that.
Fixes: 3c12de9a5c ("batman-adv: network coding - code and transmit packets if possible")
Signed-off-by: George Spelvin <lkml@sdf.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
The kernel provides a function to create random values from 0 - (max-1)
since commit f337db64af ("random32: add prandom_u32_max and convert open
coded users"). Simply use this function to replace code sections which use
prandom_u32 and a handcrafted method to map it to the correct range.
Signed-off-by: Sven Eckelmann <sven@narfation.org>
