| Commit message (Collapse) | Author | Age | Files | Lines |
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Noticed an off-by-one in the packet counter because it was incremented
before and the byte counter after the flow update.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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The RIB will now show some stats for the flow allocator, including
congestion avoidance statistics. This is needed before decoupling the
data transfer component and the flow allocator as some current stats
show in DT will move to FA.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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The mb-ecn policy has a couple of divisions in the math, which I
wanted to avoid. Now it measures the number of bytes sent in a window,
and updates the next window with AIMD logic. If the number of bytes in
the window is reached, the call blocks. To avoid long packet bursts,
the window size continually scales to contain between CA_MINPS (8) and
CA_MAXPS (64) packets.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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This adds congestion avoidance policies to the unicast IPCP. The
default policy is a multi-bit explicit congestion avoidance algorithm
based on data-center TCP congestion avoidance (DCTCP) to relay
information about the maximum queue depth that packets experienced to
the receiver. There's also a "nop" policy to disable congestion
avoidance for testing and benchmarking purposes.
The (initial) API for congestion avoidance policies is:
void * (* ctx_create)(void);
void (* ctx_destroy)(void * ctx);
These calls create / and or destroy a context for congestion control
for a specific flow. Thread-safety of the context is the
responsability of the flow allocator (operations on the ctx should be
performed under a lock).
ca_wnd_t (* ctx_update_snd)(void * ctx,
size_t len);
This is the sender call to update the context, and should be called
for every packet that is sent on the flow. The len parameter in this
API is the packet length, which allows calculating the bandwidth. It
returns an opaque union type that is used for the call to check/wait
if the congestion window is open or closed (and allowing to release
locks before waiting).
bool (* ctx_update_rcv)(void * ctx,
size_t len,
uint8_t ecn,
uint16_t * ece);
This is the call to update the flow congestion context on the receiver
side. It should be called for every received packet. It gets the ecn
value from the packet and its length, and returns the ECE (explicit
congestion experienced) value to be sent to the sender in case of
congestion. The boolean returned signals whether or not a congestion
update needs to be sent.
void (* ctx_update_ece)(void * ctx,
uint16_t ece);
This is the call for the sending side top update the context when it
receives an ECE update from the receiver.
void (* wnd_wait)(ca_wnd_t wnd);
This is a (blocking) call that waits for the congestion window to
clear. It should be stateless (to avoid waiting under locks). This may
change later on if passing the context is needed for different algorithms.
uint8_t (* calc_ecn)(int fd,
size_t len);
This is the call that intermediate IPCPs(routers) should use to update
the ECN field on passing packets.
The multi-bit ECN policy bases the value for the ECN field on the
depth of the rbuff queue packets will be sent on. I created another
call to grab the queue depth as fccntl is write-locking the
application. We can further optimize this to avoid most locking on the
rbuff.
Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>
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