passt/flow.c

/* SPDX-License-Identifier: GPL-2.0-or-later
 * Copyright Red Hat
 * Author: David Gibson <david@gibson.dropbear.id.au>
 *
 * Tracking for logical "flows" of packets.
 */

#include <stdint.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>

#include "util.h"
#include "passt.h"
#include "siphash.h"
#include "inany.h"
#include "flow.h"
#include "flow_table.h"

const char *flow_type_str[] = {
	[FLOW_TYPE_NONE]	= "<none>",
	[FLOW_TCP]		= "TCP connection",
	[FLOW_TCP_SPLICE]	= "TCP connection (spliced)",
};
static_assert(ARRAY_SIZE(flow_type_str) == FLOW_NUM_TYPES,
	      "flow_type_str[] doesn't match enum flow_type");

/* Global Flow Table */
unsigned flow_count;
union flow flowtab[FLOW_MAX];

/* Last time the flow timers ran */
static struct timespec flow_timer_run;

/** flow_log_ - Log flow-related message
 * @f:		flow the message is related to
 * @pri:	Log priority
 * @fmt:	Format string
 * @...:	printf-arguments
 */
void flow_log_(const struct flow_common *f, int pri, const char *fmt, ...)
{
	char msg[BUFSIZ];
	va_list args;

	va_start(args, fmt);
	(void)vsnprintf(msg, sizeof(msg), fmt, args);
	va_end(args);

	logmsg(pri, "Flow %u (%s): %s", flow_idx(f), FLOW_TYPE(f), msg);
}

/**
 * flow_alloc() - Allocate a new flow
 *
 * Return: pointer to an unused flow entry, or NULL if the table is full
 */
union flow *flow_alloc(void)
{
	if (flow_count >= FLOW_MAX)
		return NULL;

	return &flowtab[flow_count++];
}

/**
 * flow_alloc_cancel() - Free a newly allocated flow
 * @flow:	Flow to deallocate
 *
 * @flow must be the last flow allocated by flow_alloc()
 */
void flow_alloc_cancel(union flow *flow)
{
	ASSERT(FLOW_IDX(flow) == flow_count - 1);
	memset(flow, 0, sizeof(*flow));
	flow_count--;
}

/**
 * flow_table_compact() - Perform compaction on flow table
 * @c:		Execution context
 * @hole:	Pointer to recently closed flow
 */
static void flow_table_compact(const struct ctx *c, union flow *hole)
{
	union flow *from;

	if (FLOW_IDX(hole) == --flow_count) {
		debug("flow: table compaction: maximum index was %u (%p)",
		      FLOW_IDX(hole), (void *)hole);
		memset(hole, 0, sizeof(*hole));
		return;
	}

	from = flowtab + flow_count;
	memcpy(hole, from, sizeof(*hole));

	switch (from->f.type) {
	case FLOW_TCP:
		tcp_tap_conn_update(c, &from->tcp, &hole->tcp);
		break;
	case FLOW_TCP_SPLICE:
		tcp_splice_conn_update(c, &hole->tcp_splice);
		break;
	default:
		die("Unexpected %s in tcp_table_compact()",
		    FLOW_TYPE(&from->f));
	}

	debug("flow: table compaction (%s): old index %u, new index %u, "
	      "from: %p, to: %p",
	      FLOW_TYPE(&from->f), FLOW_IDX(from), FLOW_IDX(hole),
	      (void *)from, (void *)hole);

	memset(from, 0, sizeof(*from));
}

/**
 * flow_defer_handler() - Handler for per-flow deferred and timed tasks
 * @c:		Execution context
 * @now:	Current timestamp
 */
void flow_defer_handler(const struct ctx *c, const struct timespec *now)
{
	bool timer = false;
	union flow *flow;

	if (timespec_diff_ms(now, &flow_timer_run) >= FLOW_TIMER_INTERVAL) {
		timer = true;
		flow_timer_run = *now;
	}

	for (flow = flowtab + flow_count - 1; flow >= flowtab; flow--) {
		bool closed = false;

		switch (flow->f.type) {
		case FLOW_TCP:
			closed = tcp_flow_defer(flow);
			break;
		case FLOW_TCP_SPLICE:
			closed = tcp_splice_flow_defer(flow);
			if (!closed && timer)
				tcp_splice_timer(c, flow);
			break;
		default:
			/* Assume other flow types don't need any handling */
			;
		}

		if (closed)
			flow_table_compact(c, flow);
	}
}