MFC r325008

Fix Dummynet AQM packet marking function ecn_mark() and fq_codel /
fq_pie schedulers packet classification functions in layer2 (bridge mode).

Dummynet AQM packet marking function ecn_mark() and fq_codel/fq_pie
schedulers packet classification functions (fq_codel_classify_flow()
and fq_pie_classify_flow()) assume mbuf is pointing at L3 (IP)
packet. However, this assumption is incorrect if ipfw/dummynet is
used to manage layer2 traffic (bridge mode) since mbuf will point
at L2 frame. This patch solves this problem by identifying the
source of the frame/packet (L2 or L3) and adding ETHER_HDR_LEN
offset when converting an mbuf pointer to ip pointer if the traffic
is from layer2. More specifically, in dummynet packet tagging
function, tag_mbuf(), iphdr_off is set to ETHER_HDR_LEN if the
traffic is from layer2 and set to zero otherwise. Whenever an access
to IP header is required, mtodo(m, dn_tag_get(m)->iphdr_off) is
used instead of mtod(m, struct ip *) to correctly convert mbuf
pointer to ip pointer in both L2 and L3 traffic.

Submitted by: lstewart
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D12506

MFC r318527

Fix the queue delay estimation in PIE/FQ-PIE when the timestamp
(TS) method is used. When packet timestamp is used, the "current_qdelay"
keeps storing the last queue delay value calculated in the dequeue
function. Therefore, when a burst of packets arrives followed by
a pause, the "current_qdelay" will store a high value caused by the
burst and stick to that value during the pause because the queue
delay measurement is done inside the dequeue function. This causes
the drop probability calculation function to calculate high drop
probability value instead of zero and prevents the burst allowance
mechanism from working properly. Fix this problem by resetting
"current_qdelay" inside the drop probability calculation function
when the queue length is zero and TS option is used.

Submitted by: Rasool Al-Saadi <ralsaadi@swin.edu.au>

MFC r318511

The result of right shifting a negative signed value is implementation
defined. On machines without arithmetic shift instructions, zero bits
may be shifted in from the left, giving a large positive result instead
of the desired divide-by power-of-2. Fix this by operating on the
absolute value and compensating for the possible negation later.

Reverse the order of the underflow/overflow tests and the exponential
decay calculation to avoid the possibility of an erroneous overflow
detection if p is a sufficiently small non-negative value. Also
check for negative values of prob before doing the exponential decay
to avoid another instance of of right shifting a negative value.

Tested by: Rasool Al-Saadi <ralsaadi@swin.edu.au>

MFC r302667

Fix problems in the FQ-PIE AQM cleanup code that could leak memory or
cause a crash.

Because dummynet calls pie_cleanup() while holding a mutex, pie_cleanup()
is not able to use callout_drain() to make sure that all callouts are
finished before it returns, and callout_stop() is not sufficient to make
that guarantee. After pie_cleanup() returns, dummynet will free a
structure that any remaining callouts will want to access.

Fix these problems by allocating a separate structure to contain the
data used by the callouts. In pie_cleanup(), call callout_reset_sbt()
to replace the normal callout with a cleanup callout that does the cleanup
work for each sub-queue. The instance of the cleanup callout that
destroys the last flow will also free the extra allocated block of memory.
Protect the reference count manipulation in the cleanup callout with
DN_BH_WLOCK() to be consistent with all of the other usage of the reference
count where this lock is held by the dummynet code.

Submitted by: Rasool Al-Saadi <ralsaadi@swin.edu.au>
Approved by: re (gjb)
Differential Revision: https://reviews.freebsd.org/D7174