MINOR: dgram: allow to set rcv/sndbuf for dgram sockets as well

tune.rcvbuf.client and tune.rcvbuf.server are not suitable for shared
dgram sockets because they're per connection so their units are not the
same. However, QUIC's listener and log servers are not connected and
take per-thread or per-process traffic where a socket log buffer might
be too small, causing undesirable packet losses and retransmits in the
case of QUIC. This essentially manifests in listener mode with new
connections taking a lot of time to set up under heavy traffic due to
the small queues causing delays. Let's add a few new settings allowing
to set these shared socket sizes on the frontend and backend side (which
reminds that these are per-front/back and not per client/server hence
not per connection).

doc/configuration.txt

@@ -1212,12 +1212,16 @@ The following keywords are supported in the "global" section :
    - tune.quic.max-frame-loss
    - tune.quic.retry-threshold
    - tune.quic.socket-owner
+   - tune.rcvbuf.backend
    - tune.rcvbuf.client
+   - tune.rcvbuf.frontend
    - tune.rcvbuf.server
    - tune.recv_enough
    - tune.runqueue-depth
    - tune.sched.low-latency
+   - tune.sndbuf.backend
    - tune.sndbuf.client
+   - tune.sndbuf.frontend
    - tune.sndbuf.server
    - tune.stick-counters
    - tune.ssl.cachesize
@@ -3377,6 +3381,22 @@ tune.quic.socket-owner { connection | listener }
   is used globally, it will be forced on every listener instance, regardless of
   their individual configuration.
 
+tune.rcvbuf.backend <number>
+tune.rcvbuf.frontend <number>
+  For the kernel socket receive buffer size on non-connected sockets to this
+  size. This can be used QUIC in listener mode and log-forward on the frontend.
+  The default system buffers might sometimes be too small for sockets receiving
+  lots of aggregated traffic, causing some losses and possibly retransmits (in
+  case of QUIC), possibly slowing down connection establishment under heavy
+  traffic. The value is expressed in bytes, applied to each socket. In listener
+  mode, sockets are shared between all connections, and the total number of
+  sockets depends on the "shards" value of the "bind" line. There's no good
+  value, a good one corresponds to an expected size per connection multiplied
+  by the expected number of connections. The kernel may trim large values. See
+  also "tune.rcvbuf.client" and "tune.rcvbuf.server" for their connected socket
+  counter parts, as well as "tune.sndbuf.backend" and "tune.sndbuf.frontend"
+  for the send setting.
+
 tune.rcvbuf.client <number>
 tune.rcvbuf.server <number>
   Forces the kernel socket receive buffer size on the client or the server side
@@ -3415,6 +3435,22 @@ tune.sched.low-latency { on | off }
   massive traffic, at the expense of a higher impact on this large traffic.
   For regular usage it is better to leave this off. The default value is off.
 
+tune.sndbuf.backend <number>
+tune.sndbuf.frontend <number>
+  For the kernel socket send buffer size on non-connected sockets to this size.
+  This can be used for UNIX socket and UDP logging on the backend side, and for
+  QUIC in listener mode on the frontend. The default system buffers might
+  sometimes be too small for sockets shared between many connections (or log
+  senders), causing some losses and possibly retransmits, slowing down new
+  connection establishment under high traffic. The value is expressed in bytes,
+  applied to each socket. In listener mode, sockets are shared between all
+  connections, and the total number of sockets depends on the "shards" value of
+  the "bind" line. There's no good value, a good one corresponds to an expected
+  size per connection multiplied by the expected number of connections. The
+  kernel may trim large values. See also "tune.sndbuf.client" and
+  "tune.sndbuf.server" for their connected socket counter parts, as well as
+  "tune.rcvbuf.backend" and "tune.rcvbuf.frontend" for the receive setting.
+
 tune.sndbuf.client <number>
 tune.sndbuf.server <number>
   Forces the kernel socket send buffer size on the client or the server side to

include/haproxy/global-t.h

@@ -156,6 +156,10 @@ struct global {
 		int client_rcvbuf; /* set client rcvbuf to this value if not null */
 		int server_sndbuf; /* set server sndbuf to this value if not null */
 		int server_rcvbuf; /* set server rcvbuf to this value if not null */
+		int frontend_sndbuf; /* set frontend dgram sndbuf to this value if not null */
+		int frontend_rcvbuf; /* set frontend dgram rcvbuf to this value if not null */
+		int backend_sndbuf;  /* set backend dgram sndbuf to this value if not null */
+		int backend_rcvbuf;  /* set backend dgram rcvbuf to this value if not null */
 		int pipesize;      /* pipe size in bytes, system defaults if zero */
 		int max_http_hdr;  /* max number of HTTP headers, use MAX_HTTP_HDR if zero */
 		int requri_len;    /* max len of request URI, use REQURI_LEN if zero */

src/dgram.c

@@ -11,7 +11,10 @@
  */
 
 #include <haproxy/fd.h>
+#include <haproxy/cfgparse.h>
 #include <haproxy/dgram.h>
+#include <haproxy/errors.h>
+#include <haproxy/tools.h>
 
 /* datagram handler callback */
 void dgram_fd_handler(int fd)
@@ -28,3 +31,49 @@ void dgram_fd_handler(int fd)
 
 	return;
 }
+
+/* config parser for global "tune.{rcv,snd}buf.{frontend,backend}" */
+static int dgram_parse_tune_bufs(char **args, int section_type, struct proxy *curpx,
+                                 const struct proxy *defpx, const char *file, int line,
+                                 char **err)
+{
+	int *valptr;
+	int val;
+
+	if (too_many_args(1, args, err, NULL))
+		return -1;
+
+	/* "tune.rcvbuf.frontend", "tune.rcvbuf.backend",
+	 * "tune.sndbuf.frontend", "tune.sndbuf.backend"
+	 */
+	valptr = (args[0][5] == 'r' && args[0][12] == 'f') ? &global.tune.frontend_rcvbuf :
+		 (args[0][5] == 'r' && args[0][12] == 'b') ? &global.tune.backend_rcvbuf :
+		 (args[0][5] == 's' && args[0][12] == 'f') ? &global.tune.frontend_sndbuf :
+		 &global.tune.backend_sndbuf;
+
+	if (*valptr != 0) {
+		memprintf(err, "parsing [%s:%d] : ignoring '%s' which was already specified.\n", file, line, args[0]);
+		return 1;
+	}
+
+	val = atoi(args[1]);
+
+	if (*(args[1]) == 0 || val <= 0) {
+		memprintf(err, "parsing [%s:%d] : '%s' expects a strictly positive integer argument.\n", file, line, args[0]);
+		return -1;
+	}
+
+	*valptr = val;
+	return 0;
+}
+
+/* register "global" section keywords */
+static struct cfg_kw_list dgram_cfg_kws = {ILH, {
+	{ CFG_GLOBAL, "tune.rcvbuf.backend",  dgram_parse_tune_bufs },
+	{ CFG_GLOBAL, "tune.rcvbuf.frontend", dgram_parse_tune_bufs },
+	{ CFG_GLOBAL, "tune.sndbuf.backend",  dgram_parse_tune_bufs },
+	{ CFG_GLOBAL, "tune.sndbuf.frontend", dgram_parse_tune_bufs },
+	{ 0, NULL, NULL }
+}};
+
+INITCALL1(STG_REGISTER, cfg_register_keywords, &dgram_cfg_kws);

src/log.c

@@ -2053,6 +2053,9 @@ static inline void __do_send_log(struct log_target *target, struct log_header hd
 		} else {
 			/* we don't want to receive anything on this socket */
 			setsockopt(*plogfd, SOL_SOCKET, SO_RCVBUF, &zero, sizeof(zero));
+			/* we may want to adjust the output buffer (tune.sndbuf.backend) */
+			if (global.tune.backend_sndbuf)
+				setsockopt(*plogfd, SOL_SOCKET, SO_SNDBUF, &global.tune.backend_sndbuf, sizeof(global.tune.backend_sndbuf));
 			/* does nothing under Linux, maybe needed for others */
 			shutdown(*plogfd, SHUT_RD);
 			fd_set_cloexec(*plogfd);

src/proto_quic.c

@@ -680,6 +680,12 @@ static int quic_bind_listener(struct listener *listener, char *errmsg, int errle
 			global.tune.options &= ~GTUNE_QUIC_SOCK_PER_CONN;
 	}
 
+	if (global.tune.frontend_rcvbuf)
+		setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &global.tune.frontend_rcvbuf, sizeof(global.tune.frontend_rcvbuf));
+
+	if (global.tune.frontend_sndbuf)
+		setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &global.tune.frontend_sndbuf, sizeof(global.tune.frontend_sndbuf));
+
 	listener_set_state(listener, LI_LISTEN);
 
  udp_return:

src/proto_udp.c

@@ -148,6 +148,13 @@ int udp_bind_listener(struct listener *listener, char *errmsg, int errlen)
 		goto udp_return;
 	}
 
+	/* we may want to adjust the output buffer (tune.sndbuf.backend) */
+	if (global.tune.frontend_rcvbuf)
+		setsockopt(listener->rx.fd, SOL_SOCKET, SO_RCVBUF, &global.tune.frontend_rcvbuf, sizeof(global.tune.frontend_rcvbuf));
+
+	if (global.tune.frontend_sndbuf)
+		setsockopt(listener->rx.fd, SOL_SOCKET, SO_SNDBUF, &global.tune.frontend_sndbuf, sizeof(global.tune.frontend_sndbuf));
+
 	listener_set_state(listener, LI_LISTEN);
 
  udp_return: