SO_REUSEADDR per default on TCP LISTEN; so-reuseaddr=

CHANGES

@@ -66,6 +66,10 @@ Features:
 	With this option Socat restores the VLAN tag.
 	Feature inspired by Zhao Dong.
 
+	Socket option SO_REUSEADDR is now automatically applied to TCP LISTEN
+	addresses. reuseaddr= restores the old behaviour.
+	Tests: TCP4_REUSEADDR OPENSSL_6_REUSEADDR REUSEADDR_NULL
+
 Corrections:
 	When a sub process (EXEC, SYSTEM) terminated with exit code other than
 	0, its last sent data might have been lost depending on timing of read/

doc/socat.yo

@@ -586,7 +586,7 @@ label(ADDRESS_OPENSSL_LISTEN)dit(bf(tt(OPENSSL-LISTEN:<port>)))
    link(range)(OPTION_RANGE),
    link(tcpwrap)(OPTION_TCPWRAPPERS),
    link(su)(OPTION_SUBSTUSER),
-   link(reuseaddr)(OPTION_REUSEADDR),
+   link(reuseaddr)(OPTION_SO_REUSEADDR),
    link(retry)(OPTION_RETRY)nl()
    See also:
    link(OPENSSL)(ADDRESS_OPENSSL_CONNECT),
@@ -652,7 +652,7 @@ label(ADDRESS_OPENSSL_DTLS_SERVER)dit(bf(tt(OPENSSL-DTLS-SERVER:<port>)))
    link(range)(OPTION_RANGE),
    link(tcpwrap)(OPTION_TCPWRAPPERS),
    link(su)(OPTION_SUBSTUSER),
-   link(reuseaddr)(OPTION_REUSEADDR),
+   link(reuseaddr)(OPTION_SO_REUSEADDR),
    link(retry)(OPTION_RETRY)nl()
    link(rcvtimeo)(OPTION_SO_RCVTIMOE)nl()
    See also:
@@ -788,7 +788,7 @@ label(ADDRESS_SCTP_LISTEN)dit(bf(tt(SCTP-LISTEN:<port>)))
    link(sctp-maxseg)(OPTION_SCTP_MAXSEG),
    link(sctp-nodelay)(OPTION_SCTP_NODELAY),
    link(su)(OPTION_SUBSTUSER),
-   link(reuseaddr)(OPTION_REUSEADDR),
+   link(reuseaddr)(OPTION_SO_REUSEADDR),
    link(retry)(OPTION_RETRY)nl()
    See also:
    link(SCTP4-LISTEN)(ADDRESS_SCTP4_LISTEN),
@@ -1053,7 +1053,7 @@ label(ADDRESS_TCP_LISTEN)dit(bf(tt(TCP-LISTEN:<port>)))
    link(accept-timeout)(OPTION_ACCEPT_TIMEOUT),
    link(mss)(OPTION_MSS),
    link(su)(OPTION_SUBSTUSER),
-   link(reuseaddr)(OPTION_REUSEADDR),
+   link(reuseaddr)(OPTION_SO_REUSEADDR),
    link(retry)(OPTION_RETRY),
    link(cool-write)(OPTION_COOL_WRITE)nl()
    See also:
@@ -1413,7 +1413,7 @@ label(ADDRESS_VSOCK_LISTEN)dit(bf(tt(VSOCK-LISTEN:<port>)))
    link(max-children)(OPTION_MAX_CHILDREN),
    link(backlog)(OPTION_BACKLOG),
    link(su)(OPTION_SUBSTUSER),
-   link(reuseaddr)(OPTION_REUSEADDR),
+   link(reuseaddr)(OPTION_SO_REUSEADDR),
    link(retry)(OPTION_RETRY)nl()
    See also:
    link(VSOCK-CONNECT)(ADDRESS_VSOCK_CONNECT)
@@ -2004,9 +2004,16 @@ label(OPTION_SO_RCVTIMOE)dit(bf(tt(so-rcvtimeo=<time>, rcvtimeo=<time>)))
 label(OPTION_SO_SNDTIMOE)dit(bf(tt(so-sndtimeo=<time>, sndtimeo=<time>)))
    Like link(so-recvtimeo)(OPTION_SO_RCVTIMOE), but for code(send). Not usecase
    known.
-label(OPTION_REUSEADDR)dit(bf(tt(reuseaddr)))
+label(OPTION_RCVLOWAT)dit(bf(tt(rcvlowat=<bytes>)))
+   Specifies the minimum number of received bytes [link(int)(TYPE_INT)] until
+   the socket layer will pass the buffered data to socat(). 
+label(OPTION_SO_REUSEADDR)dit(bf(tt(reuseaddr[=[0|1]])))
    Allows other sockets to bind to an address even if parts of it (e.g. the
-   local port) are already in use by socat() (link(example)(EXAMPLE_OPTION_REUSEADDR)). 
+   local port) are already in use by socat().nl()
+   With version 1.7.5, this socket option is set automatically for TCP LISTEN
+   addresses. If you prefer the system default (no related
+   tt(setsockopt(...SO_REUSEADDR...)) call at all), use form tt(reuseaddr=).nl()
+   (link(example)(EXAMPLE_OPTION_SO_REUSEADDR)).
 label(OPTION_SNDBUF)dit(bf(tt(sndbuf=<bytes>)))
    Sets the size of the send buffer after the code(socket()) call to
    <bytes> [link(int)(TYPE_INT)].
@@ -3295,7 +3302,7 @@ connection comes in, accepts it, then connects to the remote host
 a second connection. 
 
 label(EXAMPLE_OPTION_BIND_TCP4)
-label(EXAMPLE_OPTION_REUSEADDR)
+label(EXAMPLE_OPTION_SO_REUSEADDR)
 label(EXAMPLE_OPTION_FORK)
 label(EXAMPLE_OPTION_SUBSTUSER)
 label(EXAMPLE_OPTION_RANGE)
@@ -3319,7 +3326,7 @@ link(fork)(OPTION_FORK)'ing a new
 process after each code(accept()). It provides a little security by
 link(su)(OPTION_SUBSTUSER)'ing to user 
 nobody after forking; it only permits connections from the private 10 network
-(link(range)(OPTION_RANGE)); due to link(reuseaddr)(OPTION_REUSEADDR), it
+(link(range)(OPTION_RANGE)); due to link(reuseaddr)(OPTION_SO_REUSEADDR), it
 allows immediate restart after master process's termination, even if some child
 sockets are not completely shut down.
 With link(-lmlocal2)(option_lm), socat logs to stderr until successfully
@@ -3512,7 +3519,7 @@ implements a simple network based message collector.
 For each client connecting to port 3334, a new child process is generated (option link(fork)(OPTION_FORK)).
 All data sent by the clients are link(append)(OPTION_APPEND)'ed to the file /tmp/in.log.
 If the file does not exist, socat link(creat)(OPTION_O_CREAT)'s it. 
-Option link(reuseaddr)(OPTION_REUSEADDR) allows immediate restart of the server
+Option link(reuseaddr)(OPTION_SO_REUSEADDR) allows immediate restart of the server
 process. 
 
 COMMENT(
@@ -3523,7 +3530,7 @@ For each client connecting to port 3335, a new child process is generated
 (option link(fork)(OPTION_FORK)).
 The contents of the file /tmp/motd is sent to each client.
 Messages sent by clients result in an error due to option link(rdonly)(OPTION_RDONLY).
-Option link(reuseaddr)(OPTION_REUSEADDR) allows immediate restart of the server
+Option link(reuseaddr)(OPTION_SO_REUSEADDR) allows immediate restart of the server
 process.  
 )
 COMMENT(

xio-listen.c

@@ -153,7 +153,10 @@ int _xioopen_listen(struct single *xfd, int xioflags, struct sockaddr *us, sockl
    applyopts_offset(xfd, opts);
    applyopts_cloexec(xfd->fd, opts);
 
+   /* Phase prebind */
+   xiosock_reuseaddr(xfd->fd, proto, opts);
    applyopts(xfd->fd, opts, PH_PREBIND);
+
    applyopts(xfd->fd, opts, PH_BIND);
    if (Bind(xfd->fd, (struct sockaddr *)us, uslen) < 0) {
       Msg4(level, "bind(%d, {%s}, "F_socklen"): %s", xfd->fd,

xio-socket.c

@@ -97,7 +97,7 @@ const struct optdesc opt_so_debug    = { "so-debug",    "debug", OPT_SO_DEBUG,
 const struct optdesc opt_so_acceptconn={ "so-acceptconn","acceptconn",OPT_SO_ACCEPTCONN,GROUP_SOCKET,PH_PASTSOCKET,TYPE_INT,  OFUNC_SOCKOPT, SOL_SOCKET, SO_ACCEPTCONN};
 #endif /* SO_ACCEPTCONN */
 const struct optdesc opt_so_broadcast= { "so-broadcast", "broadcast", OPT_SO_BROADCAST,GROUP_SOCKET, PH_PASTSOCKET, TYPE_INT,  OFUNC_SOCKOPT, SOL_SOCKET, SO_BROADCAST};
-const struct optdesc opt_so_reuseaddr= { "so-reuseaddr", "reuseaddr", OPT_SO_REUSEADDR,GROUP_SOCKET, PH_PREBIND, TYPE_INT,  OFUNC_SOCKOPT, SOL_SOCKET, SO_REUSEADDR};
+const struct optdesc opt_so_reuseaddr= { "so-reuseaddr", "reuseaddr", OPT_SO_REUSEADDR,GROUP_SOCKET, PH_PREBIND, TYPE_INT_NULL,  OFUNC_SOCKOPT, SOL_SOCKET, SO_REUSEADDR};
 const struct optdesc opt_so_keepalive= { "so-keepalive", "keepalive", OPT_SO_KEEPALIVE,GROUP_SOCKET, PH_FD, TYPE_INT,  OFUNC_SOCKOPT, SOL_SOCKET, SO_KEEPALIVE};
 #if HAVE_STRUCT_LINGER
 const struct optdesc opt_so_linger   = { "so-linger",    "linger",    OPT_SO_LINGER,   GROUP_SOCKET, PH_PASTSOCKET, TYPE_LINGER,OFUNC_SOCKOPT,SOL_SOCKET, SO_LINGER };
@@ -2153,3 +2153,37 @@ int xiobind(
    applyopts(xfd->fd, opts, PH_PASTBIND);
    return 0;
 }
+
+/* Handles the SO_REUSEADDR socket option for TCP LISTEN addresses depending on
+   Socat option so-reuseaddr:
+   Option not applied: set it to 1
+   Option applied with a value: set it to the value
+   Option applied eith empty value "so-reuseaddr=": do not call setsockopt() for
+   SO_REUSEADDR
+   Return 0 on success, or -1 with errno when an error occurred.
+ */
+int xiosock_reuseaddr(int fd, int ipproto, struct opt *opts)
+{
+	union integral val;
+	union integral notnull;
+	int _errno;
+
+	val.u_int = 0;
+	notnull.u_bool = false;
+	if (ipproto == IPPROTO_TCP) {
+		val.u_int = 1;
+		notnull.u_bool = true;
+	}
+	retropt_2integrals(opts, OPT_SO_REUSEADDR, &val, &notnull);
+	if (notnull.u_bool) {
+		if (Setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val.u_int, sizeof(int))
+		    != 0) {
+			_errno = errno;
+			Error4("setsockopt(%d, SOL_SOCKET, SO_REUSEADDR, { %d }, "F_Zu"): %s",
+			       fd, val.u_int, sizeof(val.u_int), strerror(errno));
+			errno = _errno;
+			return -1;
+		}
+	}
+	return 0;
+}

xio-socket.h

@@ -135,5 +135,6 @@ extern int
 xiosocket(struct opt *opts, int pf, int socktype, int proto, int level);
 extern int
 xiosocketpair(struct opt *opts, int pf, int socktype, int proto, int sv[2]);
+extern int xiosock_reuseaddr(int fd, int ipproto, struct opt *opts);
 
 #endif /* !defined(__xio_socket_h_included) */

xio-udp.c

@@ -133,24 +133,30 @@ int _xioopen_ipdgram_listen(struct single *sfd,
    while (true) {	/* we loop with fork or prohibited packets */
       /* now wait for some packet on this datagram socket, get its sender
 	 address, connect there, and return */
-      int reuseaddr = dofork;
+      union integral notnull;
+      union integral reuseaddr;
       int doreuseaddr = (dofork != 0);
       char infobuff[256];
       union sockaddr_union _sockname;
       union sockaddr_union *la = &_sockname;	/* local address */
 
+      reuseaddr.u_int = dofork;
+
       if ((sfd->fd = xiosocket(opts, pf, socktype, ipproto, E_ERROR)) < 0) {
 	 return STAT_RETRYLATER;
       }
-      doreuseaddr |= (retropt_int(opts, OPT_SO_REUSEADDR, &reuseaddr) >= 0);
+      doreuseaddr |= (retropt_2integrals(opts, OPT_SO_REUSEADDR,
+					 &reuseaddr, &notnull) >= 0);
       applyopts(sfd->fd, opts, PH_PASTSOCKET);
+
+      /* SO_REUSEADDR handling of UDP sockets is helpful on Solaris */
       if (doreuseaddr) {
 	 if (Setsockopt(sfd->fd, opt_so_reuseaddr.major,
-			opt_so_reuseaddr.minor, &reuseaddr, sizeof(reuseaddr))
+			opt_so_reuseaddr.minor, &reuseaddr.u_int, sizeof(reuseaddr.u_int))
 	     < 0) {
 	    Warn6("setsockopt(%d, %d, %d, {%d}, "F_Zd"): %s",
 		  sfd->fd, opt_so_reuseaddr.major,
-		  opt_so_reuseaddr.minor, reuseaddr, sizeof(reuseaddr),
+		  opt_so_reuseaddr.minor, reuseaddr.u_int, sizeof(reuseaddr.u_int),
 		  strerror(errno));
 	 }
       }

xioopts.c

@@ -2094,6 +2094,21 @@ int parseopts_table(const char **a, groups_t groups, struct opt **opts,
 	 Info2("setting option \"%s\" to %d", ent->desc->defname,
 	       (*opts)[i].value.u_int);
 	 break;
+      case TYPE_INT_NULL:
+	 (*opts)[i].value2.u_bool = true;
+	 if (assign && token[0] != '\0') {
+	    char *rest;
+	    (*opts)[i].value.u_int = Strtoul(token, &rest, 0, a0);
+	 } else if (assign) {
+	    (*opts)[i].value2.u_bool = false; 	/* NULL / no value */
+	    Info1("setting option \"%s\" to NULL", ent->desc->defname);
+	    break;
+	 } else {
+	    (*opts)[i].value.u_int = 1;
+	 }
+	 Info2("setting option \"%s\" to %d", ent->desc->defname,
+	       (*opts)[i].value.u_int);
+	 break;
       case TYPE_BOOL:
 	 if (!assign) {
 	    (*opts)[i].value.u_bool = 1;
@@ -2924,7 +2939,7 @@ int retropt_int(struct opt *opts, int optcode, int *result) {
 	 case TYPE_INT: *result = opt->value.u_int; break;
 	 case TYPE_STRING: *result = strtol(opt->value.u_string, &rest, 0);
 	    if (*rest != '\0') {
-	       Error1("retropts: trailing garbage in numerical arg of option \"%s\"",
+	       Error1("retropts_int(): trailing garbage in numerical arg of option \"%s\"",
 		      opt->desc->defname);
 	    }
 	    break;
@@ -2941,6 +2956,36 @@ int retropt_int(struct opt *opts, int optcode, int *result) {
    return -1;
 }
 
+/* Looks for the first option of type <optcode>. If the option is found,
+   this function stores its int value in *result, "consumes" the
+   option, and returns 0.
+   If the option is not found, *result is not modified, and -1 is returned. */
+int retropt_2integrals(struct opt *opts, int optcode,
+		       union integral *value1, union integral *value2)
+{
+   struct opt *opt = opts;
+
+   while (opt->desc != ODESC_END) {
+      if (opt->desc != ODESC_DONE && opt->desc->optcode == optcode) {
+	 switch (opt->desc->type) {
+	 case TYPE_INT_NULL:
+	 /* ...and many more types */
+	    *value1 = opt->value;
+	    *value2 = opt->value2;
+	    break;
+	 default: Error2("cannot convert type %d of option %s to int/NULL",
+			 opt->desc->type, opt->desc->defname);
+	    opt->desc = ODESC_ERROR;
+	    return -1;
+	 }
+	 opt->desc = ODESC_DONE;
+	 return 0;
+      }
+      ++opt;
+   }
+   return -1;
+}
+
 /* Looks for the first option of type <optcode>. If the option is found,
    this function stores its unsigned int value in *result, "consumes" the
    option, and returns 0.
@@ -3335,6 +3380,16 @@ int applyopts(int fd, struct opt *opts, enum e_phase phase) {
 		  opt->desc = ODESC_ERROR; ++opt; continue;
 	       }
 	       break;
+	    case TYPE_INT_NULL:
+	       if (opt->value2.u_bool &&
+		   Setsockopt(fd, opt->desc->major, opt->desc->minor,
+			      &opt->value.u_int, sizeof(int)) < 0) {
+		  Error6("setsockopt(%d, %d, %d, {%d}, "F_Zu"): %s",
+			 fd, opt->desc->major, opt->desc->minor,
+			 opt->value.u_int, sizeof(int), strerror(errno));
+		  opt->desc = ODESC_ERROR; ++opt; continue;
+	       }
+	       break;
 	    case TYPE_LONG:
 	       if (Setsockopt(fd, opt->desc->major, opt->desc->minor,
 			      &opt->value.u_long, sizeof(long)) < 0) {

xioopts.h

@@ -27,6 +27,7 @@ enum e_types {
    TYPE_BYTE,		/* unsigned char */
 
    TYPE_INT,		/* int */
+   TYPE_INT_NULL,	/* int, or opt= for no action (instead of default) */
    TYPE_LONG,		/* long */
    TYPE_STRING,		/* char * */
    TYPE_NAME = TYPE_STRING,
@@ -125,7 +126,7 @@ enum e_func {
    groups. to keep the search for options simple, we allow each option to
    belong to at most one group only. (we have a dummy GROUP_NONE for those
    that don't want to belong to any...)
-   The caller of parseopts() specifies per bitpatter a set of groups where it
+   The caller of parseopts() specifies per bit pattern a set of groups where it
    accepts options from.
 */
 
@@ -946,6 +947,7 @@ extern int retropt_bool(struct opt *opts, int optcode, bool *result);
 extern int retropt_short(struct opt *opts, int optcode, short *result);
 extern int retropt_ushort(struct opt *opts, int optcode, unsigned short *result);
 extern int retropt_int(struct opt *opts, int optcode, int *result);
+extern int retropt_2integrals(struct opt *opts, int optcode, union integral *value1, union integral *value2);
 extern int retropt_uint(struct opt *opts, int optcode, unsigned int *result);
 extern int retropt_long(struct opt *opts, int optcode, long *result);
 extern int retropt_ulong(struct opt *opts, int optcode, unsigned long *result);