xio-ip.c

/* source: xio-ip.c */
/* Copyright Gerhard Rieger 2001-2009 */
/* Published under the GNU General Public License V.2, see file COPYING */

/* this file contains the source for IP related functions */

#include "xiosysincludes.h"

#if _WITH_IP4 || _WITH_IP6

#include "xioopen.h"

#include "xio-ascii.h"
#include "xio-socket.h"
#include "xio-ip.h"
#include "xio-ip6.h"


#if WITH_IP4 || WITH_IP6

#ifdef IP_OPTIONS
const struct optdesc opt_ip_options = { "ip-options", "ipoptions", OPT_IP_OPTIONS, GROUP_SOCK_IP, PH_PASTSOCKET,TYPE_BIN, OFUNC_SOCKOPT_APPEND, SOL_IP, IP_OPTIONS };
#endif
#ifdef IP_PKTINFO
const struct optdesc opt_ip_pktinfo = { "ip-pktinfo", "pktinfo",   OPT_IP_PKTINFO, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_PKTINFO };
#endif
#ifdef IP_RECVTOS
const struct optdesc opt_ip_recvtos = { "ip-recvtos", "recvtos",   OPT_IP_RECVTOS, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVTOS };
#endif
#ifdef IP_RECVTTL	/* -Cygwin */
const struct optdesc opt_ip_recvttl = { "ip-recvttl", "recvttl",   OPT_IP_RECVTTL, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVTTL };
#endif
#ifdef IP_RECVOPTS
const struct optdesc opt_ip_recvopts= { "ip-recvopts","recvopts",  OPT_IP_RECVOPTS,GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVOPTS };
#endif
#ifdef IP_RETOPTS
const struct optdesc opt_ip_retopts = { "ip-retopts", "retopts",   OPT_IP_RETOPTS, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RETOPTS };
#endif
const struct optdesc opt_ip_tos     = { "ip-tos",     "tos",       OPT_IP_TOS,     GROUP_SOCK_IP, PH_PASTSOCKET,TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_TOS };
const struct optdesc opt_ip_ttl     = { "ip-ttl",     "ttl",       OPT_IP_TTL,     GROUP_SOCK_IP, PH_PASTSOCKET,TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_TTL };
#ifdef IP_HDRINCL
const struct optdesc opt_ip_hdrincl = { "ip-hdrincl", "hdrincl",   OPT_IP_HDRINCL, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_HDRINCL };
#endif
#ifdef IP_RECVERR
const struct optdesc opt_ip_recverr = { "ip-recverr", "recverr",   OPT_IP_RECVERR, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVERR };
#endif
#ifdef IP_MTU_DISCOVER
const struct optdesc opt_ip_mtu_discover={"ip-mtu-discover","mtudiscover",OPT_IP_MTU_DISCOVER,GROUP_SOCK_IP,PH_PASTSOCKET,TYPE_INT,OFUNC_SOCKOPT,SOL_IP,IP_MTU_DISCOVER };
#endif
#ifdef IP_MTU
const struct optdesc opt_ip_mtu     = { "ip-mtu",     "mtu",       OPT_IP_MTU,     GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_MTU };
#endif
#ifdef IP_FREEBIND
const struct optdesc opt_ip_freebind= { "ip-freebind","freebind",  OPT_IP_FREEBIND,GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_FREEBIND };
#endif
#ifdef IP_ROUTER_ALERT
const struct optdesc opt_ip_router_alert={"ip-router-alert","routeralert",OPT_IP_ROUTER_ALERT,GROUP_SOCK_IP,PH_PASTSOCKET,TYPE_INT,OFUNC_SOCKOPT,SOL_IP,IP_ROUTER_ALERT};
#endif
/* following: Linux allows int but OpenBSD reqs char/byte */
const struct optdesc opt_ip_multicast_ttl={"ip-multicast-ttl","multicastttl",OPT_IP_MULTICAST_TTL,GROUP_SOCK_IP,PH_PASTSOCKET,TYPE_BYTE,OFUNC_SOCKOPT,SOL_IP,IP_MULTICAST_TTL};
/* following: Linux allows int but OpenBSD reqs char/byte */
const struct optdesc opt_ip_multicast_loop={"ip-multicast-loop","multicastloop",OPT_IP_MULTICAST_LOOP,GROUP_SOCK_IP,PH_PASTSOCKET,TYPE_BYTE,OFUNC_SOCKOPT,SOL_IP,IP_MULTICAST_LOOP};
const struct optdesc opt_ip_multicast_if  ={"ip-multicast-if",  "multicast-if", OPT_IP_MULTICAST_IF,  GROUP_SOCK_IP,PH_PASTSOCKET,TYPE_IP4NAME,OFUNC_SOCKOPT,SOL_IP,IP_MULTICAST_IF};
#ifdef IP_PKTOPTIONS
const struct optdesc opt_ip_pktoptions = { "ip-pktoptions", "pktopts", OPT_IP_PKTOPTIONS, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_PKTOPTIONS };
#endif
#ifdef IP_ADD_MEMBERSHIP
const struct optdesc opt_ip_add_membership = { "ip-add-membership", "membership",OPT_IP_ADD_MEMBERSHIP, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_IP_MREQN, OFUNC_SOCKOPT, SOL_IP, IP_ADD_MEMBERSHIP };
#endif
#ifdef IP_RECVDSTADDR
const struct optdesc opt_ip_recvdstaddr = { "ip-recvdstaddr", "recvdstaddr",OPT_IP_RECVDSTADDR, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVDSTADDR };
#endif
#ifdef IP_RECVIF
const struct optdesc opt_ip_recvif = { "ip-recvif", "recvdstaddrif",OPT_IP_RECVIF, GROUP_SOCK_IP, PH_PASTSOCKET, TYPE_INT, OFUNC_SOCKOPT, SOL_IP, IP_RECVIF };
#endif

#if HAVE_RESOLV_H
const struct optdesc opt_res_debug    = { "res-debug",    NULL,       OPT_RES_DEBUG,    GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_DEBUG };
const struct optdesc opt_res_aaonly   = { "res-aaonly",   "aaonly",   OPT_RES_AAONLY,   GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_AAONLY };
const struct optdesc opt_res_usevc    = { "res-usevc",    "usevc",    OPT_RES_USEVC,    GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_USEVC };
const struct optdesc opt_res_primary  = { "res-primary",  "primary",  OPT_RES_PRIMARY,  GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_PRIMARY };
const struct optdesc opt_res_igntc    = { "res-igntc",    "igntc",    OPT_RES_IGNTC,    GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_IGNTC };
const struct optdesc opt_res_recurse  = { "res-recurse",  "recurse",  OPT_RES_RECURSE,  GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_RECURSE };
const struct optdesc opt_res_defnames = { "res-defnames", "defnames", OPT_RES_DEFNAMES, GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_DEFNAMES };
const struct optdesc opt_res_stayopen = { "res-stayopen", "stayopen", OPT_RES_STAYOPEN, GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_STAYOPEN };
const struct optdesc opt_res_dnsrch   = { "res-dnsrch",   "dnsrch",   OPT_RES_DNSRCH,   GROUP_SOCK_IP, PH_INIT, TYPE_BOOL, OFUNC_OFFSET_MASKS, XIO_OFFSETOF(para.socket.ip.res_opts), XIO_SIZEOF(para.socket.ip.res_opts), RES_DNSRCH };
#endif /* HAVE_RESOLV_H */

#endif /* WITH_IP4 || WITH_IP6 */


#if HAVE_RESOLV_H
int Res_init(void) {
   int result;
   Debug("res_init()");
   result = res_init();
   Debug1("res_init() -> %d", result);
   return result;
}
#endif /* HAVE_RESOLV_H */

#if HAVE_RESOLV_H
unsigned long res_opts() {
   return _res.options;
}
#endif /* HAVE_RESOLV_H */

/* the ultimate(?) socat resolver function
 node: the address to be resolved; supported forms:
   1.2.3.4 (IPv4 address)
   [::2]   (IPv6 address)
   hostname (hostname resolving to IPv4 or IPv6 address)
   hostname.domain (fq hostname resolving to IPv4 or IPv6 address)
 service: the port specification; may be numeric or symbolic
 family: PF_INET, PF_INET6, or PF_UNSPEC permitting both
 socktype: SOCK_STREAM, SOCK_DGRAM
 protocol: IPPROTO_UDP, IPPROTO_TCP
 sau: an uninitialized storage for the resulting socket address
 returns: STAT_OK, STAT_RETRYLATER
*/
int xiogetaddrinfo(const char *node, const char *service,
		   int family, int socktype, int protocol,
		   union sockaddr_union *sau, socklen_t *socklen,
		   unsigned long res_opts0, unsigned long res_opts1) {
   int port = -1;	/* port number in network byte order */
   char *numnode = NULL;
   size_t nodelen;
   unsigned long save_res_opts = 0;
#if HAVE_GETADDRINFO
   struct addrinfo hints = {0};
   struct addrinfo *res = NULL;
#else /* HAVE_GETIPNODEBYNAME || nothing */
   struct hostent *host;
#endif
   int error_num;

#if HAVE_RESOLV_H
   if (res_opts0 | res_opts1) {
      if (!(_res.options & RES_INIT)) {
         Res_init();	/*!!! returns -1 on error */
      }
      save_res_opts = _res.options;
      _res.options &= ~res_opts0;
      _res.options |= res_opts1;
      Debug2("changed _res.options from 0x%lx to 0x%lx",
	     save_res_opts, _res.options);
   }
#endif /* HAVE_RESOLV_H */
   memset(sau, 0, *socklen);
   sau->soa.sa_family = family;

   /* if service is numeric we don't want to have a lookup (might take long
      with NIS), so we handle this specially */
   if (service && isdigit(service[0]&0xff)) {
      char *extra;
      port = htons(strtoul(service, &extra, 0));
      if (*extra != '\0') {
	 Warn2("xiogetaddrinfo(, \"%s\", ...): extra trailing data \"%s\"",
	       service, extra);
      }
      service = NULL; 
   }

   /* the resolver functions might handle numeric forms of node names by
      reverse lookup, that's not what we want.
      So we detect these and handle them specially */
   if (node && isdigit(node[0]&0xff)) {
#if HAVE_GETADDRINFO
      hints.ai_flags |= AI_NUMERICHOST;
#endif /* HAVE_GETADDRINFO */
      if (family == PF_UNSPEC) {
	 family = PF_INET;
#if HAVE_GETADDRINFO
      } else if (family == PF_INET6) {
	 /* map "explicitely" into IPv6 address space; getipnodebyname() does
	    this with AI_V4MAPPED, but not getaddrinfo() */
	 if ((numnode = Malloc(strlen(node)+7+1)) == NULL) {
#if HAVE_RESOLV_H
	    if (res_opts0 | res_opts1) {
	       _res.options = (_res.options & (~res_opts0&~res_opts1) |
			       save_res_opts& ( res_opts0| res_opts1));
	    }
#endif
	    return STAT_NORETRY;
	 }
	 sprintf(numnode, "::ffff:%s", node);
	 node = numnode;
	 hints.ai_flags |= AI_NUMERICHOST;
#endif /* HAVE_GETADDRINFO */
      }
#if WITH_IP6
   } else if (node && node[0] == '[' && node[(nodelen=strlen(node))-1]==']') {
      if ((numnode = Malloc(nodelen-1)) == NULL) {
#if HAVE_RESOLV_H
	 if (res_opts0 | res_opts1) {
	    _res.options = (_res.options & (~res_opts0&~res_opts1) |
			    save_res_opts& ( res_opts0| res_opts1));
	 }
#endif
	 return STAT_NORETRY;
      }
      strncpy(numnode, node+1, nodelen-2);
      numnode[nodelen-2] = '\0';
      node = numnode;
#if HAVE_GETADDRINFO
      hints.ai_flags |= AI_NUMERICHOST;
#endif /* HAVE_GETADDRINFO */
      if (family == PF_UNSPEC)  family = PF_INET6;
#endif /* WITH_IP6 */
   }

#if HAVE_GETADDRINFO
   if (node != NULL || service != NULL) {
      struct addrinfo *record;

      if (socktype != SOCK_STREAM && socktype != SOCK_DGRAM) {
	 /* actual socket type value is not supported - fallback to a good one */
	 socktype = SOCK_DGRAM;
      }
      if (protocol != IPPROTO_TCP && protocol != IPPROTO_UDP) {
	 /* actual protocol value is not supported - fallback to a good one */
	 if (socktype == SOCK_DGRAM) {
	    protocol = IPPROTO_UDP;
	 } else {
	    protocol = IPPROTO_TCP;
	 }
      }
      hints.ai_flags |= AI_PASSIVE;
      hints.ai_family = family;
      hints.ai_socktype = socktype;
      hints.ai_protocol = protocol;
      hints.ai_addrlen = 0;
      hints.ai_addr = NULL;
      hints.ai_canonname = NULL;
      hints.ai_next = NULL;

      if ((error_num = Getaddrinfo(node, service, &hints, &res)) != 0) {
	 Error7("getaddrinfo(\"%s\", \"%s\", {%d,%d,%d,%d}, {}): %s",
		node, service, hints.ai_flags, hints.ai_family,
		hints.ai_socktype, hints.ai_protocol,
		(error_num == EAI_SYSTEM)?
		strerror(errno):gai_strerror(error_num));
	 if (res != NULL)  freeaddrinfo(res);
	 if (numnode)  free(numnode);

#if HAVE_RESOLV_H
	 if (res_opts0 | res_opts1) {
	    _res.options = (_res.options & (~res_opts0&~res_opts1) |
			    save_res_opts& ( res_opts0| res_opts1));
	 }
#endif
	 return STAT_RETRYLATER;
      }
      service = NULL;	/* do not resolve later again */

      record = res;
      if (family == PF_UNSPEC && xioopts.preferred_ip == '0') {
	 /* we just take the first result */
	 family = res[0].ai_addr->sa_family;
      }
      if (family == PF_UNSPEC) {
	 int trypf;
	 trypf = (xioopts.preferred_ip=='6'?PF_INET6:PF_INET);
	 /* we must look for a matching entry */
	 while (record != NULL) {
	    if (record->ai_family == trypf) {
	       family = trypf;
	       break;	/* family and record set accordingly */
	    }
	    record = record->ai_next;
	 }
	 if (record == NULL) {
	    /* we did not find a "preferred" entry, take the first */
	    record = res;
	    family = res[0].ai_addr->sa_family;
	 }
      }

      switch (family) {
#if WITH_IP4
      case PF_INET:
	 if (*socklen > record->ai_addrlen) {
	    *socklen = record->ai_addrlen;
	 }
	 memcpy(&sau->ip4, record->ai_addr, *socklen);
	 break;
#endif /* WITH_IP4 */
#if WITH_IP6
      case PF_INET6:
#if _AIX
	 /* older AIX versions pass wrong length, so we correct it */
	 record->ai_addr->sa_len = sizeof(struct sockaddr_in6);
#endif
	 if (*socklen > record->ai_addrlen) {
	    *socklen = record->ai_addrlen;
	 }
	 memcpy(&sau->ip6, record->ai_addr, *socklen);
	 break;
#endif /* WITH_IP6 */
      default:
	 Error1("address resolved to unknown protocol family %d",
		record->ai_addr->sa_family);
	 break;
      }
      freeaddrinfo(res);
   } else {
      switch (family) {
#if WITH_IP4
      case PF_INET:  *socklen = sizeof(sau->ip4); break;
#endif /* WITH_IP4 */
#if WITH_IP6
      case PF_INET6: *socklen = sizeof(sau->ip6); break;
#endif /* WITH_IP6 */
      }
   }

#elif HAVE_GETIPNODEBYNAME /* !HAVE_GETADDRINFO */

   if (node != NULL) {
      /* first fallback is getipnodebyname() */
      if (family == PF_UNSPEC) {
#if WITH_IP4 && WITH_IP6
	 family = xioopts.default_ip=='6'?PF_INET6:PF_INET;
#elif WITH_IP6
	 family = PF_INET6;
#else
	 family = PF_INET;
#endif
      }
      host = Getipnodebyname(node, family, AI_V4MAPPED, &error_num);
      if (host == NULL) {
	 const static char ai_host_not_found[] = "Host not found";
	 const static char ai_no_address[]     = "No address";
	 const static char ai_no_recovery[]    = "No recovery";
	 const static char ai_try_again[]      = "Try again";
	 const char *error_msg = "Unknown error";
	 switch (error_num) {
	 case HOST_NOT_FOUND: error_msg = ai_host_not_found; break;
	 case NO_ADDRESS:     error_msg = ai_no_address;
	 case NO_RECOVERY:    error_msg = ai_no_recovery;
	 case TRY_AGAIN:      error_msg = ai_try_again;
	 }
	 Error2("getipnodebyname(\"%s\", ...): %s", node, error_msg);
      } else {
	 switch (family) {
#if WITH_IP4
	 case PF_INET:
	    *socklen = sizeof(sau->ip4);
	    sau->soa.sa_family = PF_INET;
	    memcpy(&sau->ip4.sin_addr, host->h_addr_list[0], 4);
	    break;
#endif
#if WITH_IP6
	 case PF_INET6:
	    *socklen = sizeof(sau->ip6);
	    sau->soa.sa_family = PF_INET6;
	    memcpy(&sau->ip6.sin6_addr, host->h_addr_list[0], 16);
	    break;
#endif
	 }
      }
      freehostent(host);
   }

#else /* !HAVE_GETIPNODEBYNAME */

   if (node != NULL) {
      /* this is not a typical IP6 resolver function - but Linux
	 "man gethostbyname" says that the only supported address type with
	 this function is AF_INET _at present_, so maybe this fallback will
	 be useful somewhere sometimesin a future even for IP6 */
      if (family == PF_UNSPEC) {
#if WITH_IP4 && WITH_IP6
	 family = xioopts.default_ip=='6'?PF_INET6:PF_INET;
#elif WITH_IP6
	 family = PF_INET6;
#else
	 family = PF_INET;
#endif
      }
      /*!!! try gethostbyname2 for IP6 */
      if ((host = Gethostbyname(node)) == NULL) {
	 Error2("gethostbyname(\"%s\"): %s", node,
		h_errno == NETDB_INTERNAL ? strerror(errno) :
		hstrerror(h_errno));
#if HAVE_RESOLV_H
	 if (res_opts0 | res_opts1) {
	    _res.options = (_res.options & (~res_opts0&~res_opts1) |
			    save_res_opts& ( res_opts0| res_opts1));
	 }
#endif
	 return STAT_RETRYLATER;
      }
      if (host->h_addrtype != family) {
	 Error2("xioaddrinfo(): \"%s\" does not resolve to %s",
		node, family==PF_INET?"IP4":"IP6");
      } else {
	 switch (family) {
#if WITH_IP4
	 case PF_INET:
	    *socklen = sizeof(sau->ip4);
	    sau->soa.sa_family = PF_INET;
	    memcpy(&sau->ip4.sin_addr, host->h_addr_list[0], 4);
	    break;
#endif /* WITH_IP4 */
#if WITH_IP6
	 case PF_INET6:
	    *socklen = sizeof(sau->ip6);
	    sau->soa.sa_family = PF_INET6;
	    memcpy(&sau->ip6.sin6_addr, host->h_addr_list[0], 16);
	    break;
#endif /* WITH_IP6 */
	 }
      }
   }

#endif

#if WITH_TCP || WITH_UDP
   if (service) {
      port = parseport(service, protocol);
   }
   if (port >= 0) {
      switch (family) {
#if WITH_IP4
      case PF_INET:  sau->ip4.sin_port  = port; break;
#endif /* WITH_IP4 */
#if WITH_IP6
      case PF_INET6: sau->ip6.sin6_port = port; break;
#endif /* WITH_IP6 */
      }
   }      
#endif /* WITH_TCP || WITH_UDP */

   if (numnode)  free(numnode);

#if HAVE_RESOLV_H
   if (res_opts0 | res_opts1) {
      _res.options = (_res.options & (~res_opts0&~res_opts1) |
		      save_res_opts& ( res_opts0| res_opts1));
   }
#endif /* HAVE_RESOLV_H */
   return STAT_OK;
}


#if defined(HAVE_STRUCT_CMSGHDR) && defined(CMSG_DATA)
/* these are valid for IPv4 and IPv6 */
int xiolog_ancillary_ip(struct cmsghdr *cmsg, int *num,
			char *typbuff, int typlen,
			char *nambuff, int namlen,
			char *envbuff, int envlen,
			char *valbuff, int vallen) {
   const char *cmsgtype, *cmsgname = NULL, *cmsgenvn = NULL, *cmsgfmt = NULL;
   size_t msglen;
   char scratch1[16];	/* can hold an IPv4 address in ASCII */
   char scratch2[16];
   char scratch3[16];

   msglen = cmsg->cmsg_len-((char *)CMSG_DATA(cmsg)-(char *)cmsg);
   envbuff[0] = '\0';
   switch (cmsg->cmsg_type) {
   default:
      *num = 1;
      strncpy(typbuff, "IP", typlen);
      snprintf(nambuff, namlen, "type_%u", cmsg->cmsg_type);
      xiodump(CMSG_DATA(cmsg), msglen, valbuff, vallen, 0);
      return STAT_OK;
#if WITH_IP4
#if defined(IP_PKTINFO) && HAVE_STRUCT_IN_PKTINFO
   case IP_PKTINFO: {
      struct in_pktinfo *pktinfo = (struct in_pktinfo *)CMSG_DATA(cmsg);
      *num = 3;
      strncpy(typbuff, "IP_PKTINFO", typlen);
      snprintf(nambuff, namlen, "%s%c%s%c%s", "if", '\0', "locaddr", '\0', "dstaddr");
      snprintf(envbuff, envlen, "%s%c%s%c%s", "IP_IF", '\0', 
	       "IP_LOCADDR", '\0', "IP_DSTADDR");
      snprintf(valbuff, vallen, "%s%c%s%c%s",
	       xiogetifname(pktinfo->ipi_ifindex, scratch1, -1), '\0',
	       inet4addr_info(ntohl(pktinfo->ipi_spec_dst.s_addr), scratch2, sizeof(scratch2)), '\0',
	       inet4addr_info(ntohl(pktinfo->ipi_addr.s_addr), scratch3, sizeof(scratch3)));
   }
      return STAT_OK;
#endif /* defined(IP_PKTINFO) && HAVE_STRUCT_IN_PKTINFO */
#endif /* WITH_IP4 */
#ifdef IP_RECVERR
   case IP_RECVERR: {
      struct sock_extended_err *err =
	 (struct sock_extended_err *)CMSG_DATA(cmsg);
      *num = 6;
      strncpy(typbuff, "IP_RECVERR", typlen);
      snprintf(nambuff, namlen, "%s%c%s%c%s%c%s%c%s%c%s",
	       "errno", '\0', "origin", '\0', "type", '\0',
	       "code", '\0', "info", '\0', "data");
      snprintf(envbuff, envlen, "%s%c%s%c%s%c%s%c%s%c%s",
	       "IP_RECVERR_ERRNO", '\0', "IP_RECVERR_ORIGIN", '\0',
	       "IP_RECVERR_TYPE", '\0', "IP_RECVERR_CODE", '\0',
	       "IP_RECVERR_INFO", '\0', "IP_RECVERR_DATA");
      snprintf(valbuff, vallen, "%u%c%u%c%u%c%u%c%u%c%u",
	       err->ee_errno, '\0', err->ee_origin, '\0', err->ee_type, '\0',
	       err->ee_code, '\0', err->ee_info, '\0', err->ee_data);
      return STAT_OK;
   }
#endif /* IP_RECVERR */
#ifdef IP_RECVIF
   case IP_RECVIF: {
      /* spec in FreeBSD: /usr/include/net/if_dl.h */
      struct sockaddr_dl *sadl = (struct sockaddr_dl *)CMSG_DATA(cmsg);
      *num = 1;
      strncpy(typbuff, "IP_RECVIF", typlen);
      strncpy(nambuff, "if", namlen);
      strncpy(envbuff, "IP_IF", envlen);
      strncpy(valbuff,
	      xiosubstr(scratch1, sadl->sdl_data, 0, sadl->sdl_nlen), vallen);
      return STAT_OK;
   }
#endif /* defined(IP_RECVIF) */
#if WITH_IP4
#ifdef IP_RECVDSTADDR
   case IP_RECVDSTADDR:
      *num = 1;
      strncpy(typbuff, "IP_RECVDSTADDR", typlen);
      strncpy(nambuff, "dstaddr", namlen);
      strncpy(envbuff, "IP_DSTADDR", envlen);
      inet4addr_info(ntohl(*(uint32_t *)CMSG_DATA(cmsg)), valbuff, vallen);
      return STAT_OK;
#endif
#endif /* WITH_IP4 */
   case IP_OPTIONS:
#ifdef IP_RECVOPTS
   case IP_RECVOPTS:
#endif
      cmsgtype = "IP_OPTIONS"; cmsgname = "options"; cmsgfmt = NULL; break;
   case IP_TOS:
      cmsgtype = "IP_TOS";     cmsgname = "tos"; cmsgfmt = "%u"; break;
   case IP_TTL: /* Linux */
#ifdef IP_RECVTTL
   case IP_RECVTTL: /* FreeBSD */
#endif
      cmsgtype = "IP_TTL";     cmsgname = "ttl"; cmsgfmt = "%u"; break;
   }
   /* when we come here we provide a single parameter
      with type in cmsgtype, name in cmsgname, printf format in cmsgfmt */
   *num = 1;
   if (strlen(cmsgtype) >= typlen)  Fatal("buff too short");
   strncpy(typbuff, cmsgtype, typlen);
   if (strlen(cmsgname) >= namlen)  Fatal("buff too short");
   strncpy(nambuff, cmsgname, namlen);
   if (cmsgenvn) {
      if (strlen(cmsgenvn) >= envlen)  Fatal("buff too short");
      strncpy(envbuff, cmsgenvn, envlen);
   } else {
      envbuff[0] = '\0';
   }
   if (cmsgfmt != NULL) {
      snprintf(valbuff, vallen, cmsgfmt, *(unsigned char *)CMSG_DATA(cmsg));
   } else {
      xiodump(CMSG_DATA(cmsg), msglen, valbuff, vallen, 0);
   }
   return STAT_OK;
}
#endif /* defined(HAVE_STRUCT_CMSGHDR) && defined(CMSG_DATA) */

#endif /* _WITH_IP4 || _WITH_IP6 */