Added AI_PASSIVE handling and option ai-passive

CHANGES

@@ -84,6 +84,14 @@ Features:
 	New option ai-addrconfig disables name resolution to protocol families
 	that are not configured on the computer (e.g. IPv6)
 
+	Flag AI_PASSIVE is now automatically applied for LISTEN, RECV, and
+	RECVFROM type addresses, and with bind option. In addition to its
+	application to the getaddrinfo() function, when this flag is set while
+	no IP version is preferred by build, environment, option, or address
+	type, Socat chooses IPv6 because this might activate both versions (but
+	confirm option ipv6-v6only).
+	Added option ai-passive to control this flag explicitely.
+
 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

@@ -2245,6 +2245,10 @@ dit(bf(tt(ai-addrconfig[=0|1]))), dit(bf(tt(addrconfig[=0|1])))
    Sets or unsets the AI_ADDRCONFIG flag to prevent name resolution to address
    families that are not configured (e.g. IPv6). Default value is 1 in case the
    resolver does not get an address family hint.
+dit(bf(tt(ai-passive[=0|1]))), dit(bf(tt(passive[=0|1])))
+   Sets of unsets the AI_ADDRCONFIG flag for code(getaddrinfo)) calls. Default
+   is 1 for LISTEN, RECV, and RECVFROM type addresses, and with
+   link(bind)(OPTION_BIND) option. 
 label(OPTION_RES_DEBUG)dit(bf(tt(res-debug)))
 label(OPTION_RES_AAONLY)dit(bf(tt(res-aaonly)))
 label(OPTION_RES_USEVC)dit(bf(tt(res-usevc)))
@@ -2258,7 +2262,9 @@ label(OPTION_RES_DNSRCH)dit(bf(tt(res-dnsrch)))
    option flags. Append "=0" to clear a default option. See man
    NOEXPAND(resolver(5)) for more information on these options. These flags are
    per process, however socat() restores the old values after name resolution.
-   
+   Please note that these flags only affects DNS resolution, but not hosts or
+   NIS based name resolution, and they have no effect when (g)libc retrieves
+   the results from code(nscd).
 enddit()
 
 startdit()enddit()nl()

xio-ip.c

@@ -84,6 +84,9 @@ const struct optdesc opt_ip_recvif = { "ip-recvif", "recvdstaddrif",OPT_IP_RECVI
 #ifdef AI_ADDRCONFIG
 const struct optdesc opt_ai_addrconfig = { "ai-addrconfig", "addrconfig", OPT_AI_ADDRCONFIG, GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.ai_flags), XIO_SIZEOF(para.socket.ip.ai_flags), AI_ADDRCONFIG };
 #endif
+#ifdef AI_PASSIVE
+const struct optdesc opt_ai_passive    = { "ai-passive",    "passive",    OPT_AI_PASSIVE,    GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.ai_flags), XIO_SIZEOF(para.socket.ip.ai_flags), AI_PASSIVE    };
+#endif
 
 #if WITH_RES_DEPRECATED
 #  define WITH_RES_AAONLY 1

xio-ip.h

@@ -30,6 +30,7 @@ extern const struct optdesc opt_ip_recvif;
 extern const struct optdesc opt_ip_transparent;
 
 extern const struct optdesc opt_ai_addrconfig;
+extern const struct optdesc opt_ai_passive;
 
 extern const struct optdesc opt_res_debug;
 extern const struct optdesc opt_res_aaonly;

xio-ipapp.c

@@ -259,14 +259,22 @@ int _xioopen_ipapp_listen_prepare(
 	int socktype)
 {
    char *bindname = NULL;
+   int ai_flags2[2];
    int result;
 
    retropt_socket_pf(opts, pf);
 
    retropt_string(opts, OPT_BIND, &bindname);
+
+   /* Set AI_PASSIVE, except when it is explicitely disabled */
+   ai_flags2[0] = ai_flags[0];
+   ai_flags2[1] = ai_flags[1];
+   if (!(ai_flags2[1] & AI_PASSIVE))
+      ai_flags2[0] |= AI_PASSIVE;
+
    result =
 	xioresolve(bindname, portname, *pf, socktype, ipproto,
-		   us, uslen, ai_flags, res_opts);
+		   us, uslen, ai_flags2, res_opts);
    if (result != STAT_OK) {
       /*! STAT_RETRY? */
       return result;

xio-udp.c

@@ -507,6 +507,7 @@ int xioopen_udp_recvfrom(int argc, const char *argv[], struct opt *opts,
 		     int pf, int socktype, int ipproto) {
    union sockaddr_union us;
    socklen_t uslen = sizeof(us);
+   int ai_flags2[2];
    int result;
 
    if (argc != 2) {
@@ -532,9 +533,15 @@ int xioopen_udp_recvfrom(int argc, const char *argv[], struct opt *opts,
 #endif
    }
 
+   /* Set AI_PASSIVE, except when it is explicitely disabled */
+   ai_flags2[0] = xfd->stream.para.socket.ip.ai_flags[0];
+   ai_flags2[1] = xfd->stream.para.socket.ip.ai_flags[1];
+   if (!(ai_flags2[1] & AI_PASSIVE))
+      ai_flags2[0] |= AI_PASSIVE;
+
    if ((result =
 	xioresolve(NULL, argv[1], pf, socktype, ipproto, &us, &uslen,
-		   xfd->stream.para.socket.ip.ai_flags,
+		   ai_flags2,
 		   xfd->stream.para.socket.ip.res_opts))
        != STAT_OK) {
       return result;
@@ -586,6 +593,7 @@ int xioopen_udp_recv(int argc, const char *argv[], struct opt *opts,
    union sockaddr_union us;
    socklen_t uslen = sizeof(us);
    char *rangename;
+   int ai_flags2[2];
    int result;
 
    if (argc != 2) {
@@ -610,10 +618,15 @@ int xioopen_udp_recv(int argc, const char *argv[], struct opt *opts,
 #endif
    }
 
+   /* Set AI_PASSIVE, except when it is explicitely disabled */
+   ai_flags2[0] = xfd->stream.para.socket.ip.ai_flags[0];
+   ai_flags2[1] = xfd->stream.para.socket.ip.ai_flags[1];
+   if (!(ai_flags2[1] & AI_PASSIVE))
+      ai_flags2[0] |= AI_PASSIVE;
+
    if ((result =
 	xioresolve(NULL, argv[1], pf, socktype, ipproto, &us, &uslen,
-		   xfd->stream.para.socket.ip.ai_flags,
-		   xfd->stream.para.socket.ip.res_opts))
+		   ai_flags2, xfd->stream.para.socket.ip.res_opts))
        != STAT_OK) {
       return result;
    }

xioopts.c

@@ -178,6 +178,9 @@ const struct optname optionnames[] = {
 #endif
 #if defined(AI_ADDRCONFIG)
 	IF_IP	  ("ai-addrconfig", 		&opt_ai_addrconfig)
+#endif
+#if defined(AI_PASSIVE	)
+	IF_IP	  ("ai-passive", 		&opt_ai_passive)
 #endif
 	IF_INTERFACE("allmulti",	&opt_iff_allmulti)
 #if WITH_LIBWRAP && defined(HAVE_HOSTS_ALLOW_TABLE)
@@ -1251,6 +1254,9 @@ const struct optname optionnames[] = {
 	IF_TERMIOS("parodd",	&opt_parodd)
 #ifdef SO_PASSCRED
 	IF_SOCKET ("passcred",	&opt_so_passcred)
+#endif
+#if defined(AI_PASSIVE	)
+	IF_IP	  ("passive", 			&opt_ai_passive)
 #endif
 	IF_EXEC   ("path",	&opt_path)
 #ifdef TCP_PAWS	/* OSF1 */
@@ -3125,6 +3131,7 @@ int retropt_bind(struct opt *opts,
    char hostname[512], *hostp = hostname, *portp = NULL;
    size_t hostlen = sizeof(hostname)-1;
    int parsres;
+   int ai_flags2[2];
    int result;
 
    if (retropt_string(opts, OPT_BIND, &bindname) < 0) {
@@ -3180,11 +3187,18 @@ int retropt_bind(struct opt *opts,
 	    portp = bindp + strlen(portsep);
 	 }
       }
+
+      /* Set AI_PASSIVE, except when it is explicitely disabled */
+      ai_flags2[0] = ai_flags[0];
+      ai_flags2[1] = ai_flags[1];
+      if (!(ai_flags2[1] & AI_PASSIVE))
+      ai_flags2[0] |= AI_PASSIVE;
+
       if ((result =
 	   xioresolve(hostname[0]!='\0'?hostname:NULL, portp,
 		      af, socktype, ipproto,
 		      (union sockaddr_union *)sa, salen,
-		      ai_flags, res_opts))
+		      ai_flags2, res_opts))
 	  != STAT_OK) {
 	 Error("error resolving bind option");
 	 return STAT_NORETRY;

xioopts.h

@@ -203,6 +203,7 @@ enum e_func {
 enum e_optcode {
    OPT_ADDRESS_FAMILY = 1,
    OPT_AI_ADDRCONFIG, 	/* getaddrinfo() */
+   OPT_AI_PASSIVE, 	/* getaddrinfo() */
    /* these are not alphabetically, I know... */
    OPT_B0,		/* termios.c_cflag */
    OPT_B50,		/* termios.c_cflag */