Re: [PATCH 6/8] tcp: Make TCP timer state per-caller and guard global tasks

On Tue, Jun 16, 2026 at 07:10:50PM +0200, Laurent Vivier wrote:

tcp_defer_handler() uses c->tcp.timer_run, c->tcp.keepalive_run, and c->tcp.inactivity_run as global timer gates shared across all callers. In multiqueue mode, multiple qpair workers will call tcp_defer_handler() concurrently, causing races on these fields. It also unconditionally runs tcp_payload_flush(), tcp_sock_refill_init(), and tcp_splice_refill() which operate on global state.

Add timer_run, keepalive_run, and inactivity_run as parameters so each caller provides its own per-qpair timer state. Remove the now-unused fields from struct tcp_ctx and drop timer_init() which only initialised c->tcp.timer_run.

Guard tcp_payload_flush() and socket pool refills with qpair == 0 since they operate on global buffers shared across all queue pairs.

Signed-off-by: Laurent Vivier --- passt.c | 37 +++++++++++++++++-------------------- tcp.c | 51 +++++++++++++++++++++++++++++++-------------------- tcp.h | 9 ++------- 3 files changed, 50 insertions(+), 47 deletions(-)

diff --git a/passt.c b/passt.c index bebc2b99f523..ca5973e17317 100644 --- a/passt.c +++ b/passt.c @@ -96,16 +96,23 @@ struct passt_stats {

/** * post_handler() - Run periodic and deferred tasks for L4 protocol handlers - * @c: Execution context - * @now: Current timestamp - * @timer_run: Last time the flow timers ran - * @qpair: Queue pair to process + * @c: Execution context + * @now: Current timestamp + * @timer_run: Last time the flow timers ran + * @tcp_timer_run: Last time TCP timers ran + * @keepalive_run: Last time keepalives ran + * @inactivity_run: Last time inactivity scan ran + * @qpair: Queue pair to process */ static void post_handler(struct ctx *c, const struct timespec *now, - struct timespec *timer_run, unsigned int qpair) + struct timespec *timer_run, + struct timespec *tcp_timer_run, + time_t *keepalive_run, + time_t *inactivity_run, unsigned int qpair)

This is pretty bulk, and also threads several TCP specific things through this not TCP specific code path. This seems like a place where a qpair_ctx which holds these timestamps would be useful.

{ if (!c->no_tcp) - tcp_defer_handler(c, now, qpair); + tcp_defer_handler(c, now, tcp_timer_run, keepalive_run, + inactivity_run, qpair);

flow_defer_handler(c, now, timer_run, qpair); fwd_scan_ports_timer(c, now); @@ -130,16 +137,6 @@ static void random_init(struct ctx *c) srandom(seed); }

-/** - * timer_init() - Set initial timestamp for timer runs to current time - * @c: Execution context - * @now: Current timestamp - */ -static void timer_init(struct ctx *c, const struct timespec *now) -{ - c->tcp.timer_run = *now; -} - /** * proto_update_l2_buf() - Update scatter-gather L2 buffers in protocol handlers * @eth_d: Ethernet destination address, NULL if unchanged @@ -221,8 +218,9 @@ static void print_stats(const struct ctx *c, const struct passt_stats *stats, */ static void passt_worker(void *opaque, int nfds, struct epoll_event *events) { + static time_t keepalive_run, inactivity_run; static struct passt_stats stats = { 0 }; - static struct timespec flow_timer_run; + static struct timespec flow_timer_run, tcp_timer_run; struct ctx *c = opaque; struct timespec now; int i; @@ -306,7 +304,8 @@ static void passt_worker(void *opaque, int nfds, struct epoll_event *events) print_stats(c, &stats, &now); }

- post_handler(c, &now, &flow_timer_run, QPAIR_DEFAULT); + post_handler(c, &now, &flow_timer_run, &tcp_timer_run, + &keepalive_run, &inactivity_run, QPAIR_DEFAULT);

migrate_handler(c); } @@ -433,8 +432,6 @@ int main(int argc, char **argv)

isolate_postfork(&c);

- timer_init(&c, &now); - loop: /* NOLINTBEGIN(bugprone-branch-clone): intervals can be the same */ /* cppcheck-suppress [duplicateValueTernary, unmatchedSuppression] */ diff --git a/tcp.c b/tcp.c index f4fe866ba7c3..955012355d69 100644 --- a/tcp.c +++ b/tcp.c @@ -2988,17 +2988,19 @@ int tcp_init(struct ctx *c) /** * tcp_keepalive() - Send keepalives for connections which need it * @c: Execution context + * @now: Current timestamp + * @last_run: Last time keepalives ran, updated on run * @qpair: Queue pair to process */ -static void tcp_keepalive(struct ctx *c, const struct timespec *now, - unsigned int qpair) +static void tcp_keepalive(const struct ctx *c, const struct timespec *now, + time_t *last_run, unsigned int qpair) { union flow *flow;

- if (now->tv_sec - c->tcp.keepalive_run < KEEPALIVE_INTERVAL) + if (now->tv_sec - *last_run < KEEPALIVE_INTERVAL) return;

- c->tcp.keepalive_run = now->tv_sec; + *last_run = now->tv_sec;

flow_foreach_of_type(flow, FLOW_TCP) { struct tcp_tap_conn *conn = &flow->tcp; @@ -3021,18 +3023,20 @@ static void tcp_keepalive(struct ctx *c, const struct timespec *now, /** * tcp_inactivity() - Scan for and close long-inactive connections * @c: Execution context + * @now: Current timestamp + * @last_run: Last time inactivity scan ran, updated on run * @qpair: Queue pair to process */ -static void tcp_inactivity(struct ctx *c, const struct timespec *now, - unsigned int qpair) +static void tcp_inactivity(const struct ctx *c, const struct timespec *now, + time_t *last_run, unsigned int qpair) { union flow *flow;

- if (now->tv_sec - c->tcp.inactivity_run < INACTIVITY_INTERVAL) + if (now->tv_sec - *last_run < INACTIVITY_INTERVAL) return;

debug("TCP inactivity scan"); - c->tcp.inactivity_run = now->tv_sec; + *last_run = now->tv_sec;

flow_foreach_of_type(flow, FLOW_TCP) { struct tcp_tap_conn *conn = &flow->tcp; @@ -3054,27 +3058,34 @@ static void tcp_inactivity(struct ctx *c, const struct timespec *now,

/** * tcp_defer_handler() - Handler for TCP deferred tasks - * @c: Execution context - * @now: Current timestamp - * @qpair: Queue pair to process + * @c: Execution context + * @now: Current timestamp + * @timer_run: Last time TCP timers ran + * @keepalive_run: Last time keepalives ran + * @inactivity_run: Last time inactivity scan ran + * @qpair: Queue pair to process */ /* cppcheck-suppress [constParameterPointer, unmatchedSuppression] */ void tcp_defer_handler(struct ctx *c, const struct timespec *now, - unsigned int qpair) + struct timespec *timer_run, time_t *keepalive_run, + time_t *inactivity_run, unsigned int qpair)

This one is TCP specific, but it's still pretty bulky.

{ - tcp_payload_flush(c); + if (qpair == 0) + tcp_payload_flush(c);

- if (timespec_diff_ms(now, &c->tcp.timer_run) < TCP_TIMER_INTERVAL) + if (timespec_diff_ms(now, timer_run) < TCP_TIMER_INTERVAL) return;

- c->tcp.timer_run = *now; + *timer_run = *now;

- tcp_sock_refill_init(c); - if (c->mode == MODE_PASTA) - tcp_splice_refill(c); + if (qpair == 0) { + tcp_sock_refill_init(c); + if (c->mode == MODE_PASTA) + tcp_splice_refill(c); + }

- tcp_keepalive(c, now, qpair); - tcp_inactivity(c, now, qpair); + tcp_keepalive(c, now, keepalive_run, qpair); + tcp_inactivity(c, now, inactivity_run, qpair); }

/** diff --git a/tcp.h b/tcp.h index 490f1b140e44..64c75ba481bd 100644 --- a/tcp.h +++ b/tcp.h @@ -32,7 +32,8 @@ int tcp_listen(const struct ctx *c, uint8_t pif, unsigned rule, const union inany_addr *addr, const char *ifname, in_port_t port); int tcp_init(struct ctx *c); void tcp_defer_handler(struct ctx *c, const struct timespec *now, - unsigned int qpair); + struct timespec *timer_run, time_t *keepalive_run, + time_t *inactivity_run, unsigned int qpair);

void tcp_update_l2_buf(const unsigned char *eth_d);

@@ -42,24 +43,18 @@ extern bool peek_offset_cap; * struct tcp_ctx - Execution context for TCP routines * @scan_in: Port scanning state for inbound packets * @scan_out: Port scanning state for outbound packets - * @timer_run: Timestamp of most recent timer run * @pipe_size: Size of pipes for spliced connections * @rto_max: Maximum retry timeout (in s) * @syn_retries: SYN retries using exponential backoff timeout * @syn_linear_timeouts: SYN retries before using exponential backoff timeout - * @keepalive_run: Time we last issued tap-side keepalives - * @inactivity_run: Time we last scanned for inactive connections */ struct tcp_ctx { struct fwd_scan scan_in; struct fwd_scan scan_out; - struct timespec timer_run; size_t pipe_size; int rto_max; uint8_t syn_retries; uint8_t syn_linear_timeouts; - time_t keepalive_run; - time_t inactivity_run; };

#endif /* TCP_H */ -- 2.54.0

-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson