From 8e1c0e62feb4832dca2b53e51ab0e1cb8f48e5b1 Mon Sep 17 00:00:00 2001 From: Dimitri Staessens Date: Tue, 1 Dec 2020 19:19:04 +0100 Subject: ipcpd: Add congestion avoidance policies 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 Signed-off-by: Sander Vrijders --- src/ipcpd/unicast/pol/ca-nop.c | 93 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 src/ipcpd/unicast/pol/ca-nop.c (limited to 'src/ipcpd/unicast/pol/ca-nop.c') diff --git a/src/ipcpd/unicast/pol/ca-nop.c b/src/ipcpd/unicast/pol/ca-nop.c new file mode 100644 index 00000000..d0d89a2e --- /dev/null +++ b/src/ipcpd/unicast/pol/ca-nop.c @@ -0,0 +1,93 @@ +/* + * Ouroboros - Copyright (C) 2016 - 2020 + * + * Dummy Congestion Avoidance + * + * Dimitri Staessens + * Sander Vrijders + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., http://www.fsf.org/about/contact/. + */ + +#include "ca-nop.h" + +#include + +struct pol_ca_ops nop_ca_ops = { + .ctx_create = nop_ctx_create, + .ctx_destroy = nop_ctx_destroy, + .ctx_update_snd = nop_ctx_update_snd, + .ctx_update_rcv = nop_ctx_update_rcv, + .ctx_update_ece = nop_ctx_update_ece, + .wnd_wait = nop_wnd_wait, + .calc_ecn = nop_calc_ecn +}; + +void * nop_ctx_create(void) +{ + return (void *) 1; +} + +void nop_ctx_destroy(void * ctx) +{ + (void) ctx; +} + +ca_wnd_t nop_ctx_update_snd(void * ctx, + size_t len) +{ + ca_wnd_t wnd; + + (void) ctx; + (void) len; + + memset(&wnd, 0, sizeof(wnd)); + + return wnd; +} + +void nop_wnd_wait(ca_wnd_t wnd) +{ + (void) wnd; +} + +bool nop_ctx_update_rcv(void * ctx, + size_t len, + uint8_t ecn, + uint16_t * ece) +{ + (void) ctx; + (void) len; + (void) ecn; + (void) ece; + + return false; +} + +void nop_ctx_update_ece(void * ctx, + uint16_t ece) +{ + (void) ctx; + (void) ece; +} + + +uint8_t nop_calc_ecn(int fd, + size_t len) +{ + (void) fd; + (void) len; + + return 0; +} -- cgit v1.2.3