/*

 * Copyright (C) 2001-2003 FhG Fokus

 * Copyright (C) 2005-2009 Voice Sistem SRL

 *

 * This file is part of opensips, a free SIP server.

 *

 * opensips is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version

 *

 * opensips is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA

 *

 * History:

 * -------

 *  2001-??-??  created by andrei

 *  ????-??-??  lots of changes by a lot of people

 *  2003-01-23  support for determination of outbound interface added :

 *               get_out_socket (jiri)

 *  2003-01-24  reply to rport support added, contributed by

 *               Maxim Sobolev <sobomax@FreeBSD.org> and modified by andrei

 *  2003-02-11  removed calls to upd_send & tcp_send & replaced them with

 *               calls to msg_send (andrei)

 *  2003-03-19  replaced all mallocs/frees w/ pkg_malloc/pkg_free (andrei)

 *  2003-04-02  fixed get_send_socket for tcp fwd to udp (andrei)

 *  2003-04-03  added su_setport (andrei)

 *  2003-04-04  update_sock_struct_from_via now differentiates between

 *               local replies  & "normal" replies (andrei)

 *  2003-04-12  update_sock_struct_from via uses also FL_FORCE_RPORT for

 *               local replies (andrei)

 *  2003-08-21  check_self properly handles ipv6 addresses & refs   (andrei)

 *  2003-10-21  check_self updated to handle proto (andrei)

 *  2003-10-24  converted to the new socket_info lists (andrei)

 *  2004-10-10  modified check_self to use grep_sock_info (andrei)

 *  2004-11-08  added force_send_socket support in get_send_socket (andrei)

 *  2006-09-06  added new algorithm for building VIA branch parameter for

 *              stateless requests - it complies to RFC3261 requirement to be

 *              unique through time and space (bogdan)

 */

/*!

 * \file

 * \brief OpenSIPS Stateless forward support

 */

#include <string.h>

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netdb.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include "forward.h"

#include "parser/msg_parser.h"

#include "parser/parse_from.h"

#include "dprint.h"

#include "ut.h"

#include "dset.h"

#include "mem/mem.h"

#include "msg_translator.h"

#include "sr_module.h"

#include "ip_addr.h"

#include "resolve.h"

#include "net/trans.h"

#include "name_alias.h"

#include "socket_info.h"

#include "core_stats.h"

#include "blacklists.h"

#include "msg_callbacks.h"

#include "md5utils.h"

/*! \brief return a socket_info_pointer to the sending socket

 * \note As opposed to

 * get_send_socket(), which returns process's default socket, get_out_socket

 * attempts to determine the outbound interface which will be used;

 * it creates a temporary connected socket to determine it; it will

 * be very likely noticeably slower, but it can deal better with

 * multihomed hosts

 */

const struct socket_info* get_out_socket(const union sockaddr_union* to, int proto)

{

  int temp_sock;

  socklen_t len;

  union sockaddr_union from;

  const struct socket_info* si;

  struct ip_addr ip, ip_dst;

  if (proto!=PROTO_UDP) {

    LM_CRIT("can only be called for UDP\n");

    return 0;

  }

  temp_sock=socket(to->s.sa_family, SOCK_DGRAM, 0 );

  if (temp_sock==-1) {

    LM_ERR("socket() failed: %s\n", strerror(errno));

    return 0;

  }

  if (connect(temp_sock, &to->s, sockaddru_len(*to))==-1) {

    LM_ERR("connect failed: %s\n", strerror(errno));

    goto error;

  }

  len=sizeof(from);

  if (getsockname(temp_sock, &from.s, &len)==-1) {

    LM_ERR("getsockname failed: %s\n", strerror(errno));

    goto error;

  }

  su2ip_addr(&ip, &from);

  si=find_si(&ip, 0, proto);

  if (si==0) {

    LM_ERR("outbound IP %s not found as listener\n", ip_addr2a(&ip));

    goto error;

  }

  close(temp_sock);

  LM_DBG("socket determined: %p\n", si );

  return si;

error:

  su2ip_addr( &ip_dst, to);

  LM_ERR("failed to find route to %s\n", ip_addr2a(&ip_dst));

  close(temp_sock);

  return 0;

}

/*! \brief returns a socket_info pointer to the sending socket or 0 on error

 * \param msg SIP message (can be null)

 * \param to  destination socket_union pointer

 * \param proto protocol

 *

 * \note if msg!=null and msg->force_send_socket, the force_send_socket will be used

 */

const struct socket_info* get_send_socket(struct sip_msg *msg,

                    const union sockaddr_union* to, int proto)

{

  const struct socket_info* send_sock;

  /* check if send interface is not forced */

  if (msg && msg->force_send_socket){

    if (msg->force_send_socket->proto!=proto){

      LM_DBG("force_send_socket of different proto (%d)!\n", proto);

      msg->force_send_socket=find_si(&(msg->force_send_socket->address),

                      msg->force_send_socket->port_no,

                      proto);

    }

    if (msg->force_send_socket && (msg->force_send_socket->socket!=-1))

      return msg->force_send_socket;

    else{

      if (msg->force_send_socket && msg->force_send_socket->socket==-1)

        LM_WARN("not listening on the requested socket, no fork mode?\n");

      else

        LM_WARN("protocol/port mismatch\n");

    }

  };

  if (mhomed && proto==PROTO_UDP){

    send_sock=get_out_socket(to, proto);

    if ((send_sock==0) || (send_sock->socket!=-1))

      return send_sock; /* found or error*/

    else if (send_sock->socket==-1){

      LM_WARN("not listening on the requested socket, no fork mode?\n");

      /* continue: try to use some socket */

    }

  }

  send_sock=0;

  /* check if we need to change the socket (different address families -

   * eg: ipv4 -> ipv6 or ipv6 -> ipv4) */

  switch(proto){

    case PROTO_UDP:

      if (msg && msg->rcv.bind_address &&

      msg->rcv.bind_address->address.af==to->s.sa_family &&

      msg->rcv.bind_address->proto==PROTO_UDP) {

        send_sock = msg->rcv.bind_address;

        break;

      }

      /* default logic for all protos */

    default:

      /* we don't really know the sending address (we can find it out,

       * but we'll need also to see if we listen on it, and if yes on

       * which port -> too complicated*/

      send_sock = (to->s.sa_family==AF_INET) ?

        protos[proto].sendipv4 : protos[proto].sendipv6;

  }

  return send_sock;

}

/*! \brief checks if the proto: host:port is one of the address we listen on

 *

 * if port==0, the  port number is ignored

 * if proto==0 (PROTO_NONE) the protocol is ignored

 * returns 1 if true, 0 if false, -1 on error

 * WARNING: uses str2ip6 so it will overwrite any previous

 *  unsaved result of this function (static buffer)

 */

int check_self(str* host, unsigned short port, unsigned short proto)

{

  if (grep_sock_info(host, port, proto)) goto found;

  /* try to look into the aliases*/

  if (grep_aliases(host->s, host->len, port, proto)==0){

    LM_DBG("host != me\n");

    return 0;

  }

found:

  return 1;

}

static inline int set_sl_branch(struct sip_msg* msg)

{

  struct hdr_field *h_via;

  struct via_body  *b_via;

  str *branch;

  int via_parsed;

  char b_md5[MD5_LEN];

  via_parsed = 0;

  branch = 0;

  /* first VIA header must be parsed */

  for( h_via=msg->h_via1 ; h_via ; h_via=h_via->sibling ) {

    b_via = (struct via_body*)h_via->parsed;

    for( ; b_via ; b_via=b_via->next ) {

      /* check if there is any valid branch param */

      if (b_via->branch==0 || b_via->branch->value.s==0

      || b_via->branch->value.len==0 )

        continue;

      branch = &b_via->branch->value;

      /* check if the branch param has the magic cookie */

      if (branch->len <= (int)MCOOKIE_LEN

      || memcmp( branch->s, MCOOKIE, MCOOKIE_LEN)!=0 )

        continue;

      /* found a statefull branch -> use it */

      goto found;

    }

    if (!via_parsed) {

      if ( parse_headers(msg,HDR_EOH_F,0)<0 ) {

        LM_ERR("failed to parse all hdrs\n");

        return -1;

      }

      via_parsed = 1;

    }

  }

  /* no statefull branch :(.. -> use the branch from the last via */

found:

  if (branch==NULL) {

    /* no branch found :(.. -> try to use the From TAG param as 

     * a value to seed the MD5 - the From TAG is per call, so it gives

     * a bit of uniqueness; if this is empty, as a last resort, use the 

     * FROM URI (it cannot mis) */

    if ( parse_from_header(msg)!=0 )

    {

      LM_ERR("failed to extract FROM header\n");

      return -1;

    }

    if ( get_from(msg)->tag_value.len )

      branch = &get_from(msg)->tag_value;

    else

      branch = &get_from(msg)->uri;

  }

  /* make an MD5 over the found branch, to ensure a controlable 

   * length of the resulting branch */

  MD5StringArray ( b_md5, branch, 1 );

  /* and make a hash over transaction-related values */

  if ( parse_headers(msg, HDR_CALLID_F|HDR_CSEQ_F,0)==-1 ||

    msg->callid==NULL || msg->cseq==NULL )

  {

    LM_ERR("failed to extract CALLID or CSEQ hdr from SIP msg\n");

    return -1;

  }

  /* build the new branch */

  if (branch_builder(

    core_hash( &msg->callid->body, &get_cseq(msg)->number, 1<<16 ),

    0 /*labled - not used here */,

    b_md5,

    0 /*branch - not used here */,

    msg->add_to_branch_s, &msg->add_to_branch_len )==0 )

  {

    LM_ERR("branch_builder failed to construct the branch\n");

    return -1;

  }

  return 0;

}

int forward_request( struct sip_msg* msg, struct proxy_l * p)

{

  union sockaddr_union to;

  str buf;

  const struct socket_info* send_sock;

  const struct socket_info* last_sock;

  buf.s=NULL;

  /* calculate branch for outbound request - if the branch buffer is already

   * set (maybe by an upper level as TM), used it; otherwise computes

   * the branch for stateless fwd. . According to the latest discussions

   * on the topic, you should reuse the latest statefull branch

   * --bogdan */

  if ( msg->add_to_branch_len==0 ) {

    if (set_sl_branch(msg)!=0) {

      LM_ERR("unable to compute and add stateless VIA branch\n");

      goto error;

    }

  }

  msg_callback_process(msg, REQ_PRE_FORWARD, (void *)p);

  hostent2su( &to, &p->host, p->addr_idx, (p->port)?p->port:SIP_PORT);

  last_sock = 0;

  if (getb0flags(msg) & tcp_no_new_conn_bflag)

    tcp_no_new_conn = 1;

  do {

    send_sock=get_send_socket( msg, &to, p->proto);

    if (send_sock==0){

      LM_ERR("cannot forward to af %d, proto %d no corresponding"

        "listening socket\n", to.s.sa_family, p->proto);

      ser_error=E_NO_SOCKET;

      continue;

    }

    if ( last_sock!=send_sock ) {

      if (buf.s)

        pkg_free(buf.s);

      buf.s = build_req_buf_from_sip_req( msg, (unsigned int*)&buf.len,

        send_sock, p->proto, NULL, 0 /*flags*/);

      if (!buf.s){

        LM_ERR("building req buf failed\n");

        tcp_no_new_conn = 0;

        goto error;

      }

      last_sock = send_sock;

    }

    if (check_blacklists( p->proto, &to, buf.s, buf.len)) {

      LM_DBG("blocked by blacklists\n");

      ser_error=E_IP_BLOCKED;

      continue;

    }

    /* send it! */

    LM_DBG("sending:\n%.*s.\n", buf.len, buf.s);

    LM_DBG("orig. len=%d, new_len=%d, proto=%d\n",

      msg->len, buf.len, p->proto );

    if (msg_send(send_sock, p->proto, &to, 0, buf.s, buf.len, msg)<0){

      ser_error=E_SEND;

      continue;

    }

    slcb_run_req_out( msg, &buf, &to, send_sock, p->proto);

    ser_error = 0;

    break;

  }while( get_next_su( p, &to, (ser_error==E_IP_BLOCKED)?0:1)==0 );

  tcp_no_new_conn = 0;

  if (ser_error) {

    update_stat( drp_reqs, 1);

    goto error;

  }

  /* sent requests stats */

  update_stat( fwd_reqs, 1);

  pkg_free(buf.s);

  /* received_buf & line_buf will be freed in receive_msg by free_lump_list*/

  return 0;

error:

  if (buf.s) pkg_free(buf.s);

  return -1;

}

int update_sock_struct_from_via( union sockaddr_union* to,

                 struct sip_msg* msg,

                 struct via_body* via )

{

  struct hostent* he;

  str* name;

  int err;

  unsigned short port;

  port=0;

  if(via==msg->via1){

    /* _local_ reply, we ignore any rport or received value

     * (but we will send back to the original port if rport is

     *  present) */

    if ((msg->msg_flags&FL_FORCE_RPORT)||(via->rport))

      port=msg->rcv.src_port;

    else port=via->port;

    if(via->maddr)

      name= &(via->maddr->value);

    else

      name=&(via->host); /* received=ip in 1st via is ignored (it's

                not added by us so it's bad) */

  }else{

    /* "normal" reply, we use rport's & received value if present */

    if (via->rport && via->rport->value.s){

      LM_DBG("using 'rport'\n");

      port=str2s(via->rport->value.s, via->rport->value.len, &err);

      if (err){

        LM_NOTICE("bad rport value(%.*s)\n",

          via->rport->value.len,via->rport->value.s);

        port=0;

      }

    }

    if (via->maddr){

      name= &(via->maddr->value);

      if (port==0) port=via->port?via->port:SIP_PORT;

    } else if (via->received){

      LM_DBG("using 'received'\n");

      name=&(via->received->value);

      /* making sure that we won't do SRV lookup on "received" */

      if (port==0) port=via->port?via->port:SIP_PORT;

    }else{

      LM_DBG("using via host\n");

      name=&(via->host);

      if (port==0) port=via->port;

    }

  }

  LM_DBG("trying SRV lookup\n");

  he=sip_resolvehost(name, &port, &via->proto, 0, 0);

  if (he==0){

    LM_NOTICE("resolve_host(%.*s) failure\n", name->len, name->s);

    return -1;

  }

  hostent2su( to, he, 0, port);

  return 1;

}

/*! \brief removes first via & sends msg to the second */

int forward_reply(struct sip_msg* msg)

{

  char* new_buf;

  union sockaddr_union* to;

  unsigned int new_len;

  struct sr_module *mod;

  int proto;

  unsigned int id; /* used only by tcp*/

  const struct socket_info *send_sock;

  char* s;

  int len;

  to=0;

  id=0;

  new_buf=0;

  /*check if first via host = us */

  if (check_via){

    if (check_self(&msg->via1->host,

          msg->via1->port?msg->via1->port:SIP_PORT,

          msg->via1->proto)!=1){

      LM_ERR("host in first via!=me : %.*s:%d\n",

        msg->via1->host.len, msg->via1->host.s, msg->via1->port);

      /* send error msg back? */

      goto error;

    }

  }

  /* quick hack, slower for multiple modules*/

  for (mod=modules;mod;mod=mod->next){

    if ((mod->exports) && (mod->exports->response_f)){

      LM_DBG("found module %s, passing reply to it\n",

          mod->exports->name);

      if (mod->exports->response_f(msg)==0) goto skip;

    }

  }

  /* if stateless fwd was disabled, we cannot have stateless replies here*/

  if (sl_fwd_disabled)

    goto skip;

  /* we have to forward the reply stateless, so we need second via -bogdan*/

  if (parse_headers( msg, HDR_VIA2_F, 0 )==-1

    || (msg->via2==0) || (msg->via2->error!=PARSE_OK))

  {

    /* no second via => error */

    LM_ERR("no 2nd via found in [%.*s] [%.*s] reply from [%s] for callid [%.*s]\n",

      msg->first_line.u.reply.status.len, msg->first_line.u.reply.status.s,

      msg->cseq->body.len, msg->cseq->body.s,

      ip_addr2a(&msg->rcv.src_ip),

      msg->callid->body.len, msg->callid->body.s);

    goto error;

  }

  to=(union sockaddr_union*)pkg_malloc(sizeof(union sockaddr_union));

  if (to==0){

    LM_ERR("out of pkg memory\n");

    goto error;

  }

  proto=msg->via2->proto;

  if (update_sock_struct_from_via( to, msg, msg->via2 )==-1) goto error;

  if (is_tcp_based_proto(proto)){

    /* find id in i param if it exists */

    if (msg->via1->i&&msg->via1->i->value.s){

      s=msg->via1->i->value.s;

      len=msg->via1->i->value.len;

      if (reverse_hex2int(s, len, &id)<0)

        id = 0;

    }

  }

  send_sock = get_send_socket(msg, to, proto);

  new_buf = build_res_buf_from_sip_res( msg, &new_len, send_sock,0);

  if (!new_buf){

    LM_ERR("failed to build rpl from req failed\n");

    goto error;

  }

  if (msg->flags & tcp_no_new_conn_rplflag)

    tcp_no_new_conn = 1;

  if (msg_send(send_sock, proto, to, id, new_buf, new_len, msg)<0) {

    tcp_no_new_conn = 0;

    update_stat( drp_rpls, 1);

    goto error0;

  }

  tcp_no_new_conn = 0;

  update_stat( fwd_rpls, 1);

  /*

   * If no port is specified in the second via, then this

   * message output a wrong port number - zero. Despite that

   * the correct port is choosen in update_sock_struct_from_via,

   * as its visible with su_getport(to); .

   */

  LM_DBG("reply forwarded to %.*s:%d\n", msg->via2->host.len,

    msg->via2->host.s, (unsigned short) msg->via2->port);

  pkg_free(new_buf);

  pkg_free(to);

skip:

  return 0;

error:

  update_stat( err_rpls, 1);

error0:

  if (new_buf) pkg_free(new_buf);

  if (to) pkg_free(to);

  return -1;

}