linux/net/ipv4/tcp_plb.c

/* Protective Load Balancing (PLB)
 *
 * PLB was designed to reduce link load imbalance across datacenter
 * switches. PLB is a host-based optimization; it leverages congestion
 * signals from the transport layer to randomly change the path of the
 * connection experiencing sustained congestion. PLB prefers to repath
 * after idle periods to minimize packet reordering. It repaths by
 * changing the IPv6 Flow Label on the packets of a connection, which
 * datacenter switches include as part of ECMP/WCMP hashing.
 *
 * PLB is described in detail in:
 *
 *	Mubashir Adnan Qureshi, Yuchung Cheng, Qianwen Yin, Qiaobin Fu,
 *	Gautam Kumar, Masoud Moshref, Junhua Yan, Van Jacobson,
 *	David Wetherall,Abdul Kabbani:
 *	"PLB: Congestion Signals are Simple and Effective for
 *	 Network Load Balancing"
 *	In ACM SIGCOMM 2022, Amsterdam Netherlands.
 *
 */

#include <net/tcp.h>

/* Called once per round-trip to update PLB state for a connection. */
void tcp_plb_update_state(const struct sock *sk, struct tcp_plb_state *plb,
			  const int cong_ratio)
{ … }
EXPORT_SYMBOL_GPL(…);

/* Check whether recent congestion has been persistent enough to warrant
 * a load balancing decision that switches the connection to another path.
 */
void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb)
{ … }
EXPORT_SYMBOL_GPL(…);

/* Upon RTO, disallow load balancing for a while, to avoid having load
 * balancing decisions switch traffic to a black-holed path that was
 * previously avoided with a sk_rethink_txhash() call at RTO time.
 */
void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb)
{ … }
EXPORT_SYMBOL_GPL(…);