MINOR: proto: define dedicated protocol for active reverse connect

A new protocol named "reverse_connect" is created. This will be used to
instantiate connections that are opened by a reverse bind.

For the moment, only a minimal set of callbacks are defined with no real
work. This will be extended along the next patches.

Makefile

@@ -947,7 +947,8 @@ OBJS += src/mux_h2.o src/mux_fcgi.o src/mux_h1.o src/tcpcheck.o               \
         src/base64.o src/auth.o src/uri_auth.o src/time.o src/ebistree.o      \
         src/dynbuf.o src/wdt.o src/pipe.o src/init.o src/http_acl.o           \
         src/hpack-huff.o src/hpack-enc.o src/dict.o src/freq_ctr.o            \
-        src/ebtree.o src/hash.o src/dgram.o src/version.o
+        src/ebtree.o src/hash.o src/dgram.o src/version.o                     \
+        src/proto_reverse_connect.o
 
 ifneq ($(TRACE),)
   OBJS += src/calltrace.o

include/haproxy/proto_reverse_connect.h

@@ -0,0 +1,13 @@
+#ifndef _HAPROXY_PROTO_REVERSE_CONNECT_H
+#define _HAPROXY_PROTO_REVERSE_CONNECT_H
+
+#include <haproxy/listener-t.h>
+#include <haproxy/receiver-t.h>
+
+int rev_bind_receiver(struct receiver *rx, char **errmsg);
+
+int rev_bind_listener(struct listener *listener, char *errmsg, int errlen);
+
+int rev_accepting_conn(const struct receiver *rx);
+
+#endif /* _HAPROXY_PROTO_REVERSE_CONNECT_H */

include/haproxy/protocol-t.h

@@ -39,7 +39,8 @@ struct connection;
  */
 #define AF_CUST_EXISTING_FD  (AF_MAX + 1)
 #define AF_CUST_SOCKPAIR     (AF_MAX + 2)
-#define AF_CUST_MAX          (AF_MAX + 3)
+#define AF_CUST_REV_SRV      (AF_MAX + 3)
+#define AF_CUST_MAX          (AF_MAX + 4)
 
 /*
  * Test in case AF_CUST_MAX overflows the sa_family_t (unsigned int)

src/proto_reverse_connect.c

@@ -0,0 +1,49 @@
+#include <haproxy/api.h>
+#include <haproxy/errors.h>
+#include <haproxy/list.h>
+#include <haproxy/listener.h>
+#include <haproxy/protocol.h>
+
+#include <haproxy/proto_reverse_connect.h>
+
+struct proto_fam proto_fam_reverse_connect = {
+	.name = "reverse_connect",
+	.sock_domain = AF_CUST_REV_SRV,
+	.sock_family = AF_INET,
+	.bind = rev_bind_receiver,
+};
+
+struct protocol proto_reverse_connect = {
+	.name = "rev",
+
+	/* connection layer */
+	.listen  = rev_bind_listener,
+	.add     = default_add_listener,
+
+	/* address family */
+	.fam  = &proto_fam_reverse_connect,
+
+	/* socket layer */
+	.proto_type     = PROTO_TYPE_STREAM,
+	.sock_type      = SOCK_STREAM,
+	.sock_prot      = IPPROTO_TCP,
+	.rx_listening   = rev_accepting_conn,
+	.receivers      = LIST_HEAD_INIT(proto_reverse_connect.receivers),
+};
+
+int rev_bind_receiver(struct receiver *rx, char **errmsg)
+{
+	return ERR_NONE;
+}
+
+int rev_bind_listener(struct listener *listener, char *errmsg, int errlen)
+{
+	return ERR_NONE;
+}
+
+int rev_accepting_conn(const struct receiver *rx)
+{
+	return 1;
+}
+
+INITCALL1(STG_REGISTER, protocol_register, &proto_reverse_connect);

src/tools.c

@@ -1101,6 +1101,10 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
 		str2 += 9;
 		ss.ss_family = AF_CUST_SOCKPAIR;
 	}
+	else if (strncmp(str2, "rev@", 3) == 0) {
+		str2 += 4;
+		ss.ss_family = AF_CUST_REV_SRV;
+	}
 	else if (*str2 == '/') {
 		ss.ss_family = AF_UNIX;
 	}
@@ -1188,6 +1192,9 @@ struct sockaddr_storage *str2sa_range(const char *str, int *port, int *low, int
 			memcpy(un->sun_path, pfx, prefix_path_len);
 		memcpy(un->sun_path + prefix_path_len + abstract, str2, adr_len + 1 - abstract);
 	}
+	else if (ss.ss_family == AF_CUST_REV_SRV) {
+		/* Nothing to do here. */
+	}
 	else { /* IPv4 and IPv6 */
 		char *end = str2 + strlen(str2);
 		char *chr;