On Tue, 6 Feb 2024 12:17:24 +1100 David Gibson <david(a)gibson.dropbear.id.au> wrote:We maintain pools of ready-to-connect sockets in both the original and (for pasta) guest namespace to reduce latency when starting new TCP connections. If we exhaust those pools we have to take a higher latency path to get a new socket. Currently we open-code that fallback in the places we need it. To improve clarity encapsulate that into helper functions. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- tcp.c | 29 ++++++++++++++++++++++++----- tcp_conn.h | 2 +- tcp_splice.c | 46 +++++++++++++++++++++++++--------------------- 3 files changed, 50 insertions(+), 27 deletions(-) diff --git a/tcp.c b/tcp.c index e15b932f..c06d1cc4 100644 --- a/tcp.c +++ b/tcp.c @@ -1792,7 +1792,7 @@ int tcp_conn_pool_sock(int pool[]) * * Return: socket number on success, negative code if socket creation failed */ -int tcp_conn_new_sock(const struct ctx *c, sa_family_t af) +static int tcp_conn_new_sock(const struct ctx *c, sa_family_t af) { int s; @@ -1811,6 +1811,27 @@ int tcp_conn_new_sock(const struct ctx *c, sa_family_t af) return s; } +/** + * tcp_conn_sock() - Obtain a connectable socket in the host/init namespace + * @c: Execution context + * @af: Address family (AF_INET or AF_INET6) + * + * Return: Socket fd on success, -errno on failure + */ +int tcp_conn_sock(const struct ctx *c, sa_family_t af) +{ + int *pool = af == AF_INET6 ? init_sock_pool6 : init_sock_pool4; + int s; + + if ((s = tcp_conn_pool_sock(pool)) >= 0) + return s; + + /* If the pool is empty we just open a new one without refilling the + * pool to keep latency down. + */ + return tcp_conn_new_sock(c, af); +} + /** * tcp_conn_tap_mss() - Get MSS value advertised by tap/guest * @conn: Connection pointer @@ -1909,7 +1930,6 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, const struct tcphdr *th, const char *opts, size_t optlen, const struct timespec *now) { - int *pool = af == AF_INET6 ? init_sock_pool6 : init_sock_pool4; struct sockaddr_in addr4 = { .sin_family = AF_INET, .sin_port = th->dest, @@ -1931,9 +1951,8 @@ static void tcp_conn_from_tap(struct ctx *c, sa_family_t af, if (!(flow = flow_alloc())) return; - if ((s = tcp_conn_pool_sock(pool)) < 0) - if ((s = tcp_conn_new_sock(c, af)) < 0) - goto cancel; + if ((s = tcp_conn_sock(c, af)) < 0) + goto cancel; if (!c->no_map_gw) { if (af == AF_INET && IN4_ARE_ADDR_EQUAL(daddr, &c->ip4.gw)) diff --git a/tcp_conn.h b/tcp_conn.h index 20c7cb8b..e55edafe 100644 --- a/tcp_conn.h +++ b/tcp_conn.h @@ -159,7 +159,7 @@ bool tcp_flow_defer(union flow *flow); bool tcp_splice_flow_defer(union flow *flow); void tcp_splice_timer(const struct ctx *c, union flow *flow); int tcp_conn_pool_sock(int pool[]); -int tcp_conn_new_sock(const struct ctx *c, sa_family_t af); +int tcp_conn_sock(const struct ctx *c, sa_family_t af); void tcp_sock_refill_pool(const struct ctx *c, int pool[], sa_family_t af); void tcp_splice_refill(const struct ctx *c); diff --git a/tcp_splice.c b/tcp_splice.c index 576fe9be..609f3242 100644 --- a/tcp_splice.c +++ b/tcp_splice.c @@ -90,7 +90,7 @@ static const char *tcp_splice_flag_str[] __attribute((__unused__)) = { }; /* Forward declaration */ -static int tcp_sock_refill_ns(void *arg); +static int tcp_conn_sock_ns(const struct ctx *c, sa_family_t af); /** * tcp_splice_conn_epoll_events() - epoll events masks for given state @@ -380,36 +380,19 @@ static int tcp_splice_connect(const struct ctx *c, struct tcp_splice_conn *conn, static int tcp_splice_new(const struct ctx *c, struct tcp_splice_conn *conn, in_port_t port, uint8_t pif) { + sa_family_t af = CONN_V6(conn) ? AF_INET6 : AF_INET; int s = -1; - /* If the pool is empty we take slightly different approaches - * for init or ns sockets. For init sockets we just open a - * new one without refilling the pool to keep latency down. - * For ns sockets, we're going to incur the latency of - * entering the ns anyway, so we might as well refill the - * pool. - */ if (pif == PIF_SPLICE) { - int *p = CONN_V6(conn) ? init_sock_pool6 : init_sock_pool4; - sa_family_t af = CONN_V6(conn) ? AF_INET6 : AF_INET; - port += c->tcp.fwd_out.delta[port]; - s = tcp_conn_pool_sock(p); - if (s < 0) - s = tcp_conn_new_sock(c, af); + s = tcp_conn_sock(c, af); } else { - int *p = CONN_V6(conn) ? ns_sock_pool6 : ns_sock_pool4; - ASSERT(pif == PIF_HOST); port += c->tcp.fwd_in.delta[port]; - /* If pool is empty, refill it first */ - if (p[TCP_SOCK_POOL_SIZE-1] < 0) - NS_CALL(tcp_sock_refill_ns, c); - - s = tcp_conn_pool_sock(p); + s = tcp_conn_sock_ns(c, af); } if (s < 0) { @@ -709,6 +692,27 @@ static int tcp_sock_refill_ns(void *arg) return 0; } +/** + * tcp_conn_sock_ns() - Obtain a connectable socket in the namespace + * @c: Execution context + * @af: Address family (AF_INET or AF_INET6) + * + * Return: Socket fd in the namespace on success, -errno on failure + */ +static int tcp_conn_sock_ns(const struct ctx *c, sa_family_t af) +{ + int *p = af == AF_INET6 ? ns_sock_pool6 : ns_sock_pool4; + + /* If the pool is empty we have to incur the latency of entering the ns. + * Therefore, we might as well refill the whole pool while we're at it, + * which differs from tcp_conn_sock(). + */ + if (p[TCP_SOCK_POOL_SIZE-1] < 0)Nit, for consistency (but yes, it was already like this): if (p[TCP_SOCK_POOL_SIZE - 1] < 0) -- Stefano