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tcp, tcp_splice: Helpers for getting sockets from the pools

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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.  While we're at it, give
those helpers clearer error reporting.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-02-19 18:56:50 +11:00 committed by Stefano Brivio
parent fbe81decbd
commit fe27ebce5c
3 changed files with 62 additions and 29 deletions
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32
tcp.c
View file

@ -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 +1811,32 @@ 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.
*/
if ((s = tcp_conn_new_sock(c, af)) >= 0)
return s;
err("TCP: Unable to open socket for new connection: %s",
strerror(-s));
return -1;
}
/**
* tcp_conn_tap_mss() - Get MSS value advertised by tap/guest
* @conn: Connection pointer
@ -1909,7 +1935,6 @@ 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,
@ -1931,8 +1956,7 @@ 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)
if ((s = tcp_conn_sock(c, af)) < 0)
goto cancel;
if (!c->no_map_gw) {

2
tcp_conn.h
View file

@ -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);
int tcp_sock_refill_pool(const struct ctx *c, int pool[], sa_family_t af);
void tcp_splice_refill(const struct ctx *c);

55
tcp_splice.c
View file

@ -376,6 +376,34 @@ static int tcp_splice_connect(const struct ctx *c, struct tcp_splice_conn *conn,
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;
int s;
if ((s = tcp_conn_pool_sock(p)) >= 0)
return s;
/* 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.
* This differs from tcp_conn_sock().
*/
NS_CALL(tcp_sock_refill_ns, c);
if ((s = tcp_conn_pool_sock(p)) >= 0)
return s;
err("TCP: No available ns sockets for new connection");
return -1;
}
/**
* tcp_splice_new() - Handle new spliced connection
* @c: Execution context
@ -388,38 +416,19 @@ 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;
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);
/* 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) {
warn("Couldn't open connectable socket for splice (%d)", s);
if (s < 0)
return s;
}
return tcp_splice_connect(c, conn, s, port);
}