lib/sockopt.c

   1 /* setsockopt functions
   2  * Copyright (C) 1999 Kunihiro Ishiguro
   3  *
   4  * This file is part of GNU Zebra.
   5  *
   6  * GNU Zebra is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * GNU Zebra is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with GNU Zebra; see the file COPYING.  If not, write to the Free
  18  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  19  * 02111-1307, USA.
  20  */
  21
  22 #include <zebra.h>
  23 #include "log.h"
  24 #include "sockopt.h"
  25 #include "sockunion.h"
  26
  27 int
  28 setsockopt_so_recvbuf (int sock, int size)
  29 {
  30   int ret;
  31
  32   if ( (ret = setsockopt (sock, SOL_SOCKET, SO_RCVBUF, (char *)
  33                           &size, sizeof (int))) < 0)
  34     zlog_err ("fd %d: can't setsockopt SO_RCVBUF to %d: %s",
  35               sock,size,safe_strerror(errno));
  36
  37   return ret;
  38 }
  39
  40 int
  41 setsockopt_so_sendbuf (const int sock, int size)
  42 {
  43   int ret = setsockopt (sock, SOL_SOCKET, SO_SNDBUF,
  44     (char *)&size, sizeof (int));
  45
  46   if (ret < 0)
  47     zlog_err ("fd %d: can't setsockopt SO_SNDBUF to %d: %s",
  48       sock, size, safe_strerror (errno));
  49
  50   return ret;
  51 }
  52
  53 int
  54 getsockopt_so_sendbuf (const int sock)
  55 {
  56   u_int32_t optval;
  57   socklen_t optlen = sizeof (optval);
  58   int ret = getsockopt (sock, SOL_SOCKET, SO_SNDBUF,
  59     (char *)&optval, &optlen);
  60   if (ret < 0)
  61   {
  62     zlog_err ("fd %d: can't getsockopt SO_SNDBUF: %d (%s)",
  63       sock, errno, safe_strerror (errno));
  64     return ret;
  65   }
  66   return optval;
  67 }
  68
  69 static void *
  70 getsockopt_cmsg_data (struct msghdr *msgh, int level, int type)
  71 {
  72   struct cmsghdr *cmsg;
  73   void *ptr = NULL;
  74
  75   for (cmsg = ZCMSG_FIRSTHDR(msgh);
  76        cmsg != NULL;
  77        cmsg = CMSG_NXTHDR(msgh, cmsg))
  78     if (cmsg->cmsg_level == level && cmsg->cmsg_type)
  79       return (ptr = CMSG_DATA(cmsg));
  80
  81   return NULL;
  82 }
  83
  84 #ifdef HAVE_IPV6
  85 /* Set IPv6 packet info to the socket. */
  86 int
  87 setsockopt_ipv6_pktinfo (int sock, int val)
  88 {
  89   int ret;
  90
  91 #ifdef IPV6_RECVPKTINFO         /*2292bis-01*/
  92   ret = setsockopt(sock, IPPROTO_IPV6, IPV6_RECVPKTINFO, &val, sizeof(val));
  93   if (ret < 0)
  94     zlog_warn ("can't setsockopt IPV6_RECVPKTINFO : %s", safe_strerror (errno));
  95 #else   /*RFC2292*/
  96   ret = setsockopt(sock, IPPROTO_IPV6, IPV6_PKTINFO, &val, sizeof(val));
  97   if (ret < 0)
  98     zlog_warn ("can't setsockopt IPV6_PKTINFO : %s", safe_strerror (errno));
  99 #endif /* INIA_IPV6 */
 100   return ret;
 101 }
 102
 103 /* Set multicast hops val to the socket. */
 104 int
 105 setsockopt_ipv6_checksum (int sock, int val)
 106 {
 107   int ret;
 108
 109 #ifdef GNU_LINUX
 110   ret = setsockopt(sock, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
 111 #else
 112   ret = setsockopt(sock, IPPROTO_IPV6, IPV6_CHECKSUM, &val, sizeof(val));
 113 #endif /* GNU_LINUX */
 114   if (ret < 0)
 115     zlog_warn ("can't setsockopt IPV6_CHECKSUM");
 116   return ret;
 117 }
 118
 119 /* Set multicast hops val to the socket. */
 120 int
 121 setsockopt_ipv6_multicast_hops (int sock, int val)
 122 {
 123   int ret;
 124
 125   ret = setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
 126   if (ret < 0)
 127     zlog_warn ("can't setsockopt IPV6_MULTICAST_HOPS");
 128   return ret;
 129 }
 130
 131 /* Set multicast hops val to the socket. */
 132 int
 133 setsockopt_ipv6_unicast_hops (int sock, int val)
 134 {
 135   int ret;
 136
 137   ret = setsockopt(sock, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
 138   if (ret < 0)
 139     zlog_warn ("can't setsockopt IPV6_UNICAST_HOPS");
 140   return ret;
 141 }
 142
 143 int
 144 setsockopt_ipv6_hoplimit (int sock, int val)
 145 {
 146   int ret;
 147
 148 #ifdef IPV6_RECVHOPLIMIT        /*2292bis-01*/
 149   ret = setsockopt (sock, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &val, sizeof(val));
 150   if (ret < 0)
 151     zlog_warn ("can't setsockopt IPV6_RECVHOPLIMIT");
 152 #else   /*RFC2292*/
 153   ret = setsockopt (sock, IPPROTO_IPV6, IPV6_HOPLIMIT, &val, sizeof(val));
 154   if (ret < 0)
 155     zlog_warn ("can't setsockopt IPV6_HOPLIMIT");
 156 #endif
 157   return ret;
 158 }
 159
 160 /* Set multicast loop zero to the socket. */
 161 int
 162 setsockopt_ipv6_multicast_loop (int sock, int val)
 163 {
 164   int ret;
 165
 166   ret = setsockopt (sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &val,
 167                     sizeof (val));
 168   if (ret < 0)
 169     zlog_warn ("can't setsockopt IPV6_MULTICAST_LOOP");
 170   return ret;
 171 }
 172
 173 static int
 174 getsockopt_ipv6_ifindex (struct msghdr *msgh)
 175 {
 176   struct in6_pktinfo *pktinfo;
 177
 178   pktinfo = getsockopt_cmsg_data (msgh, IPPROTO_IPV6, IPV6_PKTINFO);
 179
 180   return pktinfo->ipi6_ifindex;
 181 }
 182
 183 int
 184 setsockopt_ipv6_tclass(int sock, int tclass)
 185 {
 186   int ret = 0;
 187
 188 #ifdef IPV6_TCLASS /* RFC3542 */
 189   ret = setsockopt (sock, IPPROTO_IPV6, IPV6_TCLASS, &tclass, sizeof (tclass));
 190   if (ret < 0)
 191     zlog_warn ("Can't set IPV6_TCLASS option for fd %d to %#x: %s",
 192                sock, tclass, safe_strerror(errno));
 193 #endif
 194   return ret;
 195 }
 196 #endif /* HAVE_IPV6 */
 197
 198 /*
 199  * Process multicast socket options for IPv4 in an OS-dependent manner.
 200  * Supported options are IP_{ADD,DROP}_MEMBERSHIP.
 201  *
 202  * Many operating systems have a limit on the number of groups that
 203  * can be joined per socket (where each group and local address
 204  * counts).  This impacts OSPF, which joins groups on each interface
 205  * using a single socket.  The limit is typically 20, derived from the
 206  * original BSD multicast implementation.  Some systems have
 207  * mechanisms for increasing this limit.
 208  *
 209  * In many 4.4BSD-derived systems, multicast group operations are not
 210  * allowed on interfaces that are not UP.  Thus, a previous attempt to
 211  * leave the group may have failed, leaving it still joined, and we
 212  * drop/join quietly to recover.  This may not be necessary, but aims to
 213  * defend against unknown behavior in that we will still return an error
 214  * if the second join fails.  It is not clear how other systems
 215  * (e.g. Linux, Solaris) behave when leaving groups on down interfaces,
 216  * but this behavior should not be harmful if they behave the same way,
 217  * allow leaves, or implicitly leave all groups joined to down interfaces.
 218  */
 219 int
 220 setsockopt_ipv4_multicast(int sock,
 221                         int optname,
 222                         struct in_addr if_addr,
 223                         unsigned int mcast_addr,
 224                         ifindex_t ifindex)
 225 {
 226 #ifdef HAVE_RFC3678
 227   struct group_req gr;
 228   struct sockaddr_in *si;
 229   int ret;
 230   memset (&gr, 0, sizeof(gr));
 231   si = (struct sockaddr_in *)&gr.gr_group;
 232   gr.gr_interface = ifindex;
 233   si->sin_family = AF_INET;
 234 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
 235   si->sin_len = sizeof(struct sockaddr_in);
 236 #endif /* HAVE_STRUCT_SOCKADDR_IN_SIN_LEN */
 237   si->sin_addr.s_addr = mcast_addr;
 238   ret = setsockopt(sock, IPPROTO_IP, (optname == IP_ADD_MEMBERSHIP) ?
 239     MCAST_JOIN_GROUP : MCAST_LEAVE_GROUP, (void *)&gr, sizeof(gr));
 240   if ((ret < 0) && (optname == IP_ADD_MEMBERSHIP) && (errno == EADDRINUSE))
 241     {
 242       setsockopt(sock, IPPROTO_IP, MCAST_LEAVE_GROUP, (void *)&gr, sizeof(gr));
 243       ret = setsockopt(sock, IPPROTO_IP, MCAST_JOIN_GROUP, (void *)&gr, sizeof(gr));
 244     }
 245   return ret;
 246
 247 #elif defined(HAVE_STRUCT_IP_MREQN_IMR_IFINDEX) && !defined(__FreeBSD__)
 248   struct ip_mreqn mreqn;
 249   int ret;
 250
 251   assert(optname == IP_ADD_MEMBERSHIP || optname == IP_DROP_MEMBERSHIP);
 252   memset (&mreqn, 0, sizeof(mreqn));
 253
 254   mreqn.imr_multiaddr.s_addr = mcast_addr;
 255   mreqn.imr_ifindex = ifindex;
 256
 257   ret = setsockopt(sock, IPPROTO_IP, optname,
 258                    (void *)&mreqn, sizeof(mreqn));
 259   if ((ret < 0) && (optname == IP_ADD_MEMBERSHIP) && (errno == EADDRINUSE))
 260     {
 261       /* see above: handle possible problem when interface comes back up */
 262       char buf[1][INET_ADDRSTRLEN];
 263       zlog_info("setsockopt_ipv4_multicast attempting to drop and "
 264                 "re-add (fd %d, mcast %s, ifindex %u)",
 265                 sock,
 266                 inet_ntop(AF_INET, &mreqn.imr_multiaddr,
 267                           buf[0], sizeof(buf[0])), ifindex);
 268       setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
 269                  (void *)&mreqn, sizeof(mreqn));
 270       ret = setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
 271                        (void *)&mreqn, sizeof(mreqn));
 272     }
 273   return ret;
 274
 275   /* Example defines for another OS, boilerplate off other code in this
 276      function, AND handle optname as per other sections for consistency !! */
 277   /* #elif  defined(BOGON_NIX) && EXAMPLE_VERSION_CODE > -100000 */
 278   /* Add your favourite OS here! */
 279
 280 #elif defined(HAVE_BSD_STRUCT_IP_MREQ_HACK) /* #if OS_TYPE */
 281   /* standard BSD API */
 282
 283   struct ip_mreq mreq;
 284   int ret;
 285
 286   assert(optname == IP_ADD_MEMBERSHIP || optname == IP_DROP_MEMBERSHIP);
 287
 288
 289   memset (&mreq, 0, sizeof(mreq));
 290   mreq.imr_multiaddr.s_addr = mcast_addr;
 291 #if !defined __OpenBSD__
 292   mreq.imr_interface.s_addr = htonl (ifindex);
 293 #else
 294   mreq.imr_interface.s_addr = if_addr.s_addr;
 295 #endif
 296
 297   ret = setsockopt (sock, IPPROTO_IP, optname, (void *)&mreq, sizeof(mreq));
 298   if ((ret < 0) && (optname == IP_ADD_MEMBERSHIP) && (errno == EADDRINUSE))
 299     {
 300       /* see above: handle possible problem when interface comes back up */
 301       char buf[1][INET_ADDRSTRLEN];
 302       zlog_info("setsockopt_ipv4_multicast attempting to drop and "
 303                 "re-add (fd %d, mcast %s, ifindex %u)",
 304                 sock,
 305                 inet_ntop(AF_INET, &mreq.imr_multiaddr,
 306                           buf[0], sizeof(buf[0])), ifindex);
 307       setsockopt (sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
 308                   (void *)&mreq, sizeof(mreq));
 309       ret = setsockopt (sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
 310                         (void *)&mreq, sizeof(mreq));
 311     }
 312   return ret;
 313
 314 #else
 315   #error "Unsupported multicast API"
 316 #endif /* #if OS_TYPE */
 317
 318 }
 319
 320 /*
 321  * Set IP_MULTICAST_IF socket option in an OS-dependent manner.
 322  */
 323 int
 324 setsockopt_ipv4_multicast_if(int sock, struct in_addr if_addr,
 325                              ifindex_t ifindex)
 326 {
 327
 328 #ifdef HAVE_STRUCT_IP_MREQN_IMR_IFINDEX
 329   struct ip_mreqn mreqn;
 330   memset (&mreqn, 0, sizeof(mreqn));
 331
 332   mreqn.imr_ifindex = ifindex;
 333   return setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF, (void *)&mreqn, sizeof(mreqn));
 334
 335   /* Example defines for another OS, boilerplate off other code in this
 336      function */
 337   /* #elif  defined(BOGON_NIX) && EXAMPLE_VERSION_CODE > -100000 */
 338   /* Add your favourite OS here! */
 339 #elif defined(HAVE_BSD_STRUCT_IP_MREQ_HACK)
 340   struct in_addr m;
 341
 342 #if !defined __OpenBSD__
 343   m.s_addr = htonl (ifindex);
 344 #else
 345   m.s_addr = if_addr.s_addr;
 346 #endif
 347
 348   return setsockopt (sock, IPPROTO_IP, IP_MULTICAST_IF, (void *)&m, sizeof(m));
 349 #else
 350   #error "Unsupported multicast API"
 351 #endif
 352 }
 353
 354 static int
 355 setsockopt_ipv4_ifindex (int sock, ifindex_t val)
 356 {
 357   int ret;
 358
 359 #if defined (IP_PKTINFO)
 360   if ((ret = setsockopt (sock, IPPROTO_IP, IP_PKTINFO, &val, sizeof (val))) < 0)
 361     zlog_warn ("Can't set IP_PKTINFO option for fd %d to %d: %s",
 362                sock,val,safe_strerror(errno));
 363 #elif defined (IP_RECVIF)
 364   if ((ret = setsockopt (sock, IPPROTO_IP, IP_RECVIF, &val, sizeof (val))) < 0)
 365     zlog_warn ("Can't set IP_RECVIF option for fd %d to %d: %s",
 366                sock,val,safe_strerror(errno));
 367 #else
 368 #warning "Neither IP_PKTINFO nor IP_RECVIF is available."
 369 #warning "Will not be able to receive link info."
 370 #warning "Things might be seriously broken.."
 371   /* XXX Does this ever happen?  Should there be a zlog_warn message here? */
 372   ret = -1;
 373 #endif
 374   return ret;
 375 }
 376
 377 int
 378 setsockopt_ipv4_tos(int sock, int tos)
 379 {
 380   int ret;
 381
 382   ret = setsockopt (sock, IPPROTO_IP, IP_TOS, &tos, sizeof (tos));
 383   if (ret < 0)
 384     zlog_warn ("Can't set IP_TOS option for fd %d to %#x: %s",
 385                sock, tos, safe_strerror(errno));
 386   return ret;
 387 }
 388
 389
 390 int
 391 setsockopt_ifindex (int af, int sock, ifindex_t val)
 392 {
 393   int ret = -1;
 394
 395   switch (af)
 396     {
 397       case AF_INET:
 398         ret = setsockopt_ipv4_ifindex (sock, val);
 399         break;
 400 #ifdef HAVE_IPV6
 401       case AF_INET6:
 402         ret = setsockopt_ipv6_pktinfo (sock, val);
 403         break;
 404 #endif
 405       default:
 406         zlog_warn ("setsockopt_ifindex: unknown address family %d", af);
 407     }
 408   return ret;
 409 }
 410
 411 /*
 412  * Requires: msgh is not NULL and points to a valid struct msghdr, which
 413  * may or may not have control data about the incoming interface.
 414  *
 415  * Returns the interface index (small integer >= 1) if it can be
 416  * determined, or else 0.
 417  */
 418 static ifindex_t
 419 getsockopt_ipv4_ifindex (struct msghdr *msgh)
 420 {
 421   /* XXX: initialize to zero?  (Always overwritten, so just cosmetic.) */
 422   ifindex_t ifindex = -1;
 423
 424 #if defined(IP_PKTINFO)
 425 /* Linux pktinfo based ifindex retrieval */
 426   struct in_pktinfo *pktinfo;
 427
 428   pktinfo =
 429     (struct in_pktinfo *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_PKTINFO);
 430   /* XXX Can pktinfo be NULL?  Clean up post 0.98. */
 431   ifindex = pktinfo->ipi_ifindex;
 432
 433 #elif defined(IP_RECVIF)
 434
 435   /* retrieval based on IP_RECVIF */
 436
 437 #ifndef SUNOS_5
 438   /* BSD systems use a sockaddr_dl as the control message payload. */
 439   struct sockaddr_dl *sdl;
 440 #else
 441   /* SUNOS_5 uses an integer with the index. */
 442   ifindex_t *ifindex_p;
 443 #endif /* SUNOS_5 */
 444
 445 #ifndef SUNOS_5
 446   /* BSD */
 447   sdl =
 448     (struct sockaddr_dl *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_RECVIF);
 449   if (sdl != NULL)
 450     ifindex = sdl->sdl_index;
 451   else
 452     ifindex = 0;
 453 #else
 454   /*
 455    * Solaris.  On Solaris 8, IP_RECVIF is defined, but the call to
 456    * enable it fails with errno=99, and the struct msghdr has
 457    * controllen 0.
 458    */
 459   ifindex_p = (uint_t *)getsockopt_cmsg_data (msgh, IPPROTO_IP, IP_RECVIF);
 460   if (ifindex_p != NULL)
 461     ifindex = *ifindex_p;
 462   else
 463     ifindex = 0;
 464 #endif /* SUNOS_5 */
 465
 466 #else
 467   /*
 468    * Neither IP_PKTINFO nor IP_RECVIF defined - warn at compile time.
 469    * XXX Decide if this is a core service, or if daemons have to cope.
 470    * Since Solaris 8 and OpenBSD seem not to provide it, it seems that
 471    * daemons have to cope.
 472    */
 473 #warning "getsockopt_ipv4_ifindex: Neither IP_PKTINFO nor IP_RECVIF defined."
 474 #warning "Some daemons may fail to operate correctly!"
 475   ifindex = 0;
 476
 477 #endif /* IP_PKTINFO */
 478
 479   return ifindex;
 480 }
 481
 482 /* return ifindex, 0 if none found */
 483 ifindex_t
 484 getsockopt_ifindex (int af, struct msghdr *msgh)
 485 {
 486   switch (af)
 487     {
 488       case AF_INET:
 489         return (getsockopt_ipv4_ifindex (msgh));
 490         break;
 491 #ifdef HAVE_IPV6
 492       case AF_INET6:
 493         return (getsockopt_ipv6_ifindex (msgh));
 494         break;
 495 #endif
 496       default:
 497         zlog_warn ("getsockopt_ifindex: unknown address family %d", af);
 498         return 0;
 499     }
 500 }
 501
 502 /* swab iph between order system uses for IP_HDRINCL and host order */
 503 void
 504 sockopt_iphdrincl_swab_htosys (struct ip *iph)
 505 {
 506   /* BSD and derived take iph in network order, except for
 507    * ip_len and ip_off
 508    */
 509 #ifndef HAVE_IP_HDRINCL_BSD_ORDER
 510   iph->ip_len = htons(iph->ip_len);
 511   iph->ip_off = htons(iph->ip_off);
 512 #endif /* HAVE_IP_HDRINCL_BSD_ORDER */
 513
 514   iph->ip_id = htons(iph->ip_id);
 515 }
 516
 517 void
 518 sockopt_iphdrincl_swab_systoh (struct ip *iph)
 519 {
 520 #ifndef HAVE_IP_HDRINCL_BSD_ORDER
 521   iph->ip_len = ntohs(iph->ip_len);
 522   iph->ip_off = ntohs(iph->ip_off);
 523 #endif /* HAVE_IP_HDRINCL_BSD_ORDER */
 524
 525   iph->ip_id = ntohs(iph->ip_id);
 526 }
 527
 528 int
 529 sockopt_tcp_rtt (int sock)
 530 {
 531 #ifdef TCP_INFO
 532   struct tcp_info ti;
 533   socklen_t len = sizeof(ti);
 534
 535   if (getsockopt (sock, IPPROTO_TCP, TCP_INFO, &ti, &len) != 0)
 536     return 0;
 537
 538   return ti.tcpi_rtt / 1000;
 539 #else
 540   return 0;
 541 #endif
 542 }
 543
 544 int
 545 sockopt_tcp_signature (int sock, union sockunion *su, const char *password)
 546 {
 547 #if defined(HAVE_TCP_MD5_LINUX24) && defined(GNU_LINUX)
 548   /* Support for the old Linux 2.4 TCP-MD5 patch, taken from Hasso Tepper's
 549    * version of the Quagga patch (based on work by Rick Payne, and Bruce
 550    * Simpson)
 551    */
 552 #define TCP_MD5_AUTH 13
 553 #define TCP_MD5_AUTH_ADD 1
 554 #define TCP_MD5_AUTH_DEL 2
 555   struct tcp_rfc2385_cmd {
 556     u_int8_t     command;    /* Command - Add/Delete */
 557     u_int32_t    address;    /* IPV4 address associated */
 558     u_int8_t     keylen;     /* MD5 Key len (do NOT assume 0 terminated ascii) */
 559     void         *key;       /* MD5 Key */
 560   } cmd;
 561   struct in_addr *addr = &su->sin.sin_addr;
 562
 563   cmd.command = (password != NULL ? TCP_MD5_AUTH_ADD : TCP_MD5_AUTH_DEL);
 564   cmd.address = addr->s_addr;
 565   cmd.keylen = (password != NULL ? strlen (password) : 0);
 566   cmd.key = password;
 567
 568   return setsockopt (sock, IPPROTO_TCP, TCP_MD5_AUTH, &cmd, sizeof cmd);
 569
 570 #elif HAVE_DECL_TCP_MD5SIG
 571   int ret;
 572 #ifndef GNU_LINUX
 573   /*
 574    * XXX Need to do PF_KEY operation here to add/remove an SA entry,
 575    * and add/remove an SP entry for this peer's packet flows also.
 576    */
 577   int md5sig = password && *password ? 1 : 0;
 578 #else
 579   int keylen = password ? strlen (password) : 0;
 580   struct tcp_md5sig md5sig;
 581   union sockunion *su2, *susock;
 582
 583   /* Figure out whether the socket and the sockunion are the same family..
 584    * adding AF_INET to AF_INET6 needs to be v4 mapped, you'd think..
 585    */
 586   if (!(susock = sockunion_getsockname (sock)))
 587     return -1;
 588
 589   if (susock->sa.sa_family == su->sa.sa_family)
 590     su2 = su;
 591   else
 592     {
 593       /* oops.. */
 594       su2 = susock;
 595
 596       if (su2->sa.sa_family == AF_INET)
 597         {
 598           sockunion_free (susock);
 599           return 0;
 600         }
 601
 602 #ifdef HAVE_IPV6
 603       /* If this does not work, then all users of this sockopt will need to
 604        * differentiate between IPv4 and IPv6, and keep seperate sockets for
 605        * each.
 606        *
 607        * Sadly, it doesn't seem to work at present. It's unknown whether
 608        * this is a bug or not.
 609        */
 610       if (su2->sa.sa_family == AF_INET6
 611           && su->sa.sa_family == AF_INET)
 612         {
 613            su2->sin6.sin6_family = AF_INET6;
 614            /* V4Map the address */
 615            memset (&su2->sin6.sin6_addr, 0, sizeof (struct in6_addr));
 616            su2->sin6.sin6_addr.s6_addr32[2] = htonl(0xffff);
 617            memcpy (&su2->sin6.sin6_addr.s6_addr32[3], &su->sin.sin_addr, 4);
 618         }
 619 #endif
 620     }
 621
 622   memset (&md5sig, 0, sizeof (md5sig));
 623   memcpy (&md5sig.tcpm_addr, su2, sizeof (*su2));
 624   md5sig.tcpm_keylen = keylen;
 625   if (keylen)
 626     memcpy (md5sig.tcpm_key, password, keylen);
 627   sockunion_free (susock);
 628 #endif /* GNU_LINUX */
 629   if ((ret = setsockopt (sock, IPPROTO_TCP, TCP_MD5SIG, &md5sig, sizeof md5sig)) < 0)
 630     {
 631       /* ENOENT is harmless.  It is returned when we clear a password for which
 632          one was not previously set. */
 633       if (ENOENT == errno)
 634         ret = 0;
 635       else
 636         zlog_err ("sockopt_tcp_signature: setsockopt(%d): %s",
 637                   sock, safe_strerror(errno));
 638     }
 639   return ret;
 640 #else /* HAVE_TCP_MD5SIG */
 641   return -2;
 642 #endif /* !HAVE_TCP_MD5SIG */
 643 }