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ipv4.c

/*
 *  net/dccp/ipv4.c
 *
 *  An implementation of the DCCP protocol
 *  Arnaldo Carvalho de Melo <acme@conectiva.com.br>
 *
 *    This program 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.
 */

#include <linux/dccp.h>
#include <linux/icmp.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/random.h>

#include <net/icmp.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/inet_sock.h>
#include <net/protocol.h>
#include <net/sock.h>
#include <net/timewait_sock.h>
#include <net/tcp_states.h>
#include <net/xfrm.h>

#include "ackvec.h"
#include "ccid.h"
#include "dccp.h"
#include "feat.h"

/*
 * This is the global socket data structure used for responding to
 * the Out-of-the-blue (OOTB) packets. A control sock will be created
 * for this socket at the initialization time.
 */
static struct socket *dccp_v4_ctl_socket;

static int dccp_v4_get_port(struct sock *sk, const unsigned short snum)
{
      return inet_csk_get_port(&dccp_hashinfo, sk, snum,
                         inet_csk_bind_conflict);
}

int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
      struct inet_sock *inet = inet_sk(sk);
      struct dccp_sock *dp = dccp_sk(sk);
      const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
      struct rtable *rt;
      __be32 daddr, nexthop;
      int tmp;
      int err;

      dp->dccps_role = DCCP_ROLE_CLIENT;

      if (addr_len < sizeof(struct sockaddr_in))
            return -EINVAL;

      if (usin->sin_family != AF_INET)
            return -EAFNOSUPPORT;

      nexthop = daddr = usin->sin_addr.s_addr;
      if (inet->opt != NULL && inet->opt->srr) {
            if (daddr == 0)
                  return -EINVAL;
            nexthop = inet->opt->faddr;
      }

      tmp = ip_route_connect(&rt, nexthop, inet->saddr,
                         RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
                         IPPROTO_DCCP,
                         inet->sport, usin->sin_port, sk, 1);
      if (tmp < 0)
            return tmp;

      if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
            ip_rt_put(rt);
            return -ENETUNREACH;
      }

      if (inet->opt == NULL || !inet->opt->srr)
            daddr = rt->rt_dst;

      if (inet->saddr == 0)
            inet->saddr = rt->rt_src;
      inet->rcv_saddr = inet->saddr;

      inet->dport = usin->sin_port;
      inet->daddr = daddr;

      inet_csk(sk)->icsk_ext_hdr_len = 0;
      if (inet->opt != NULL)
            inet_csk(sk)->icsk_ext_hdr_len = inet->opt->optlen;
      /*
       * Socket identity is still unknown (sport may be zero).
       * However we set state to DCCP_REQUESTING and not releasing socket
       * lock select source port, enter ourselves into the hash tables and
       * complete initialization after this.
       */
      dccp_set_state(sk, DCCP_REQUESTING);
      err = inet_hash_connect(&dccp_death_row, sk);
      if (err != 0)
            goto failure;

      err = ip_route_newports(&rt, IPPROTO_DCCP, inet->sport, inet->dport,
                        sk);
      if (err != 0)
            goto failure;

      /* OK, now commit destination to socket.  */
      sk_setup_caps(sk, &rt->u.dst);

      dp->dccps_iss = secure_dccp_sequence_number(inet->saddr, inet->daddr,
                                        inet->sport, inet->dport);
      inet->id = dp->dccps_iss ^ jiffies;

      err = dccp_connect(sk);
      rt = NULL;
      if (err != 0)
            goto failure;
out:
      return err;
failure:
      /*
       * This unhashes the socket and releases the local port, if necessary.
       */
      dccp_set_state(sk, DCCP_CLOSED);
      ip_rt_put(rt);
      sk->sk_route_caps = 0;
      inet->dport = 0;
      goto out;
}

EXPORT_SYMBOL_GPL(dccp_v4_connect);

/*
 * This routine does path mtu discovery as defined in RFC1191.
 */
static inline void dccp_do_pmtu_discovery(struct sock *sk,
                                const struct iphdr *iph,
                                u32 mtu)
{
      struct dst_entry *dst;
      const struct inet_sock *inet = inet_sk(sk);
      const struct dccp_sock *dp = dccp_sk(sk);

      /* We are not interested in DCCP_LISTEN and request_socks (RESPONSEs
       * send out by Linux are always < 576bytes so they should go through
       * unfragmented).
       */
      if (sk->sk_state == DCCP_LISTEN)
            return;

      /* We don't check in the destentry if pmtu discovery is forbidden
       * on this route. We just assume that no packet_to_big packets
       * are send back when pmtu discovery is not active.
       * There is a small race when the user changes this flag in the
       * route, but I think that's acceptable.
       */
      if ((dst = __sk_dst_check(sk, 0)) == NULL)
            return;

      dst->ops->update_pmtu(dst, mtu);

      /* Something is about to be wrong... Remember soft error
       * for the case, if this connection will not able to recover.
       */
      if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
            sk->sk_err_soft = EMSGSIZE;

      mtu = dst_mtu(dst);

      if (inet->pmtudisc != IP_PMTUDISC_DONT &&
          inet_csk(sk)->icsk_pmtu_cookie > mtu) {
            dccp_sync_mss(sk, mtu);

            /*
             * From RFC 4340, sec. 14.1:
             *
             *    DCCP-Sync packets are the best choice for upward
             *    probing, since DCCP-Sync probes do not risk application
             *    data loss.
             */
            dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
      } /* else let the usual retransmit timer handle it */
}

/*
 * This routine is called by the ICMP module when it gets some sort of error
 * condition. If err < 0 then the socket should be closed and the error
 * returned to the user. If err > 0 it's just the icmp type << 8 | icmp code.
 * After adjustment header points to the first 8 bytes of the tcp header. We
 * need to find the appropriate port.
 *
 * The locking strategy used here is very "optimistic". When someone else
 * accesses the socket the ICMP is just dropped and for some paths there is no
 * check at all. A more general error queue to queue errors for later handling
 * is probably better.
 */
static void dccp_v4_err(struct sk_buff *skb, u32 info)
{
      const struct iphdr *iph = (struct iphdr *)skb->data;
      const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data +
                                          (iph->ihl << 2));
      struct dccp_sock *dp;
      struct inet_sock *inet;
      const int type = icmp_hdr(skb)->type;
      const int code = icmp_hdr(skb)->code;
      struct sock *sk;
      __u64 seq;
      int err;

      if (skb->len < (iph->ihl << 2) + 8) {
            ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
            return;
      }

      sk = inet_lookup(&dccp_hashinfo, iph->daddr, dh->dccph_dport,
                   iph->saddr, dh->dccph_sport, inet_iif(skb));
      if (sk == NULL) {
            ICMP_INC_STATS_BH(ICMP_MIB_INERRORS);
            return;
      }

      if (sk->sk_state == DCCP_TIME_WAIT) {
            inet_twsk_put(inet_twsk(sk));
            return;
      }

      bh_lock_sock(sk);
      /* If too many ICMPs get dropped on busy
       * servers this needs to be solved differently.
       */
      if (sock_owned_by_user(sk))
            NET_INC_STATS_BH(LINUX_MIB_LOCKDROPPEDICMPS);

      if (sk->sk_state == DCCP_CLOSED)
            goto out;

      dp = dccp_sk(sk);
      seq = dccp_hdr_seq(dh);
      if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_LISTEN) &&
          !between48(seq, dp->dccps_swl, dp->dccps_swh)) {
            NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
            goto out;
      }

      switch (type) {
      case ICMP_SOURCE_QUENCH:
            /* Just silently ignore these. */
            goto out;
      case ICMP_PARAMETERPROB:
            err = EPROTO;
            break;
      case ICMP_DEST_UNREACH:
            if (code > NR_ICMP_UNREACH)
                  goto out;

            if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
                  if (!sock_owned_by_user(sk))
                        dccp_do_pmtu_discovery(sk, iph, info);
                  goto out;
            }

            err = icmp_err_convert[code].errno;
            break;
      case ICMP_TIME_EXCEEDED:
            err = EHOSTUNREACH;
            break;
      default:
            goto out;
      }

      switch (sk->sk_state) {
            struct request_sock *req , **prev;
      case DCCP_LISTEN:
            if (sock_owned_by_user(sk))
                  goto out;
            req = inet_csk_search_req(sk, &prev, dh->dccph_dport,
                                iph->daddr, iph->saddr);
            if (!req)
                  goto out;

            /*
             * ICMPs are not backlogged, hence we cannot get an established
             * socket here.
             */
            BUG_TRAP(!req->sk);

            if (seq != dccp_rsk(req)->dreq_iss) {
                  NET_INC_STATS_BH(LINUX_MIB_OUTOFWINDOWICMPS);
                  goto out;
            }
            /*
             * Still in RESPOND, just remove it silently.
             * There is no good way to pass the error to the newly
             * created socket, and POSIX does not want network
             * errors returned from accept().
             */
            inet_csk_reqsk_queue_drop(sk, req, prev);
            goto out;

      case DCCP_REQUESTING:
      case DCCP_RESPOND:
            if (!sock_owned_by_user(sk)) {
                  DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
                  sk->sk_err = err;

                  sk->sk_error_report(sk);

                  dccp_done(sk);
            } else
                  sk->sk_err_soft = err;
            goto out;
      }

      /* If we've already connected we will keep trying
       * until we time out, or the user gives up.
       *
       * rfc1122 4.2.3.9 allows to consider as hard errors
       * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
       * but it is obsoleted by pmtu discovery).
       *
       * Note, that in modern internet, where routing is unreliable
       * and in each dark corner broken firewalls sit, sending random
       * errors ordered by their masters even this two messages finally lose
       * their original sense (even Linux sends invalid PORT_UNREACHs)
       *
       * Now we are in compliance with RFCs.
       *                                        --ANK (980905)
       */

      inet = inet_sk(sk);
      if (!sock_owned_by_user(sk) && inet->recverr) {
            sk->sk_err = err;
            sk->sk_error_report(sk);
      } else /* Only an error on timeout */
            sk->sk_err_soft = err;
out:
      bh_unlock_sock(sk);
      sock_put(sk);
}

static inline __sum16 dccp_v4_csum_finish(struct sk_buff *skb,
                              __be32 src, __be32 dst)
{
      return csum_tcpudp_magic(src, dst, skb->len, IPPROTO_DCCP, skb->csum);
}

void dccp_v4_send_check(struct sock *sk, int unused, struct sk_buff *skb)
{
      const struct inet_sock *inet = inet_sk(sk);
      struct dccp_hdr *dh = dccp_hdr(skb);

      dccp_csum_outgoing(skb);
      dh->dccph_checksum = dccp_v4_csum_finish(skb, inet->saddr, inet->daddr);
}

EXPORT_SYMBOL_GPL(dccp_v4_send_check);

static inline u64 dccp_v4_init_sequence(const struct sk_buff *skb)
{
      return secure_dccp_sequence_number(ip_hdr(skb)->daddr,
                                 ip_hdr(skb)->saddr,
                                 dccp_hdr(skb)->dccph_dport,
                                 dccp_hdr(skb)->dccph_sport);
}

/*
 * The three way handshake has completed - we got a valid ACK or DATAACK -
 * now create the new socket.
 *
 * This is the equivalent of TCP's tcp_v4_syn_recv_sock
 */
struct sock *dccp_v4_request_recv_sock(struct sock *sk, struct sk_buff *skb,
                               struct request_sock *req,
                               struct dst_entry *dst)
{
      struct inet_request_sock *ireq;
      struct inet_sock *newinet;
      struct sock *newsk;

      if (sk_acceptq_is_full(sk))
            goto exit_overflow;

      if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
            goto exit;

      newsk = dccp_create_openreq_child(sk, req, skb);
      if (newsk == NULL)
            goto exit;

      sk_setup_caps(newsk, dst);

      newinet              = inet_sk(newsk);
      ireq           = inet_rsk(req);
      newinet->daddr       = ireq->rmt_addr;
      newinet->rcv_saddr = ireq->loc_addr;
      newinet->saddr       = ireq->loc_addr;
      newinet->opt         = ireq->opt;
      ireq->opt      = NULL;
      newinet->mc_index  = inet_iif(skb);
      newinet->mc_ttl      = ip_hdr(skb)->ttl;
      newinet->id    = jiffies;

      dccp_sync_mss(newsk, dst_mtu(dst));

      __inet_hash(&dccp_hashinfo, newsk, 0);
      __inet_inherit_port(&dccp_hashinfo, sk, newsk);

      return newsk;

exit_overflow:
      NET_INC_STATS_BH(LINUX_MIB_LISTENOVERFLOWS);
exit:
      NET_INC_STATS_BH(LINUX_MIB_LISTENDROPS);
      dst_release(dst);
      return NULL;
}

EXPORT_SYMBOL_GPL(dccp_v4_request_recv_sock);

static struct sock *dccp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
{
      const struct dccp_hdr *dh = dccp_hdr(skb);
      const struct iphdr *iph = ip_hdr(skb);
      struct sock *nsk;
      struct request_sock **prev;
      /* Find possible connection requests. */
      struct request_sock *req = inet_csk_search_req(sk, &prev,
                                           dh->dccph_sport,
                                           iph->saddr, iph->daddr);
      if (req != NULL)
            return dccp_check_req(sk, skb, req, prev);

      nsk = inet_lookup_established(&dccp_hashinfo,
                              iph->saddr, dh->dccph_sport,
                              iph->daddr, dh->dccph_dport,
                              inet_iif(skb));
      if (nsk != NULL) {
            if (nsk->sk_state != DCCP_TIME_WAIT) {
                  bh_lock_sock(nsk);
                  return nsk;
            }
            inet_twsk_put(inet_twsk(nsk));
            return NULL;
      }

      return sk;
}

static struct dst_entry* dccp_v4_route_skb(struct sock *sk,
                                 struct sk_buff *skb)
{
      struct rtable *rt;
      struct flowi fl = { .oif = ((struct rtable *)skb->dst)->rt_iif,
                      .nl_u = { .ip4_u =
                              { .daddr = ip_hdr(skb)->saddr,
                              .saddr = ip_hdr(skb)->daddr,
                              .tos = RT_CONN_FLAGS(sk) } },
                      .proto = sk->sk_protocol,
                      .uli_u = { .ports =
                               { .sport = dccp_hdr(skb)->dccph_dport,
                               .dport = dccp_hdr(skb)->dccph_sport }
                             }
                    };

      security_skb_classify_flow(skb, &fl);
      if (ip_route_output_flow(&rt, &fl, sk, 0)) {
            IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
            return NULL;
      }

      return &rt->u.dst;
}

static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
                         struct dst_entry *dst)
{
      int err = -1;
      struct sk_buff *skb;

      /* First, grab a route. */

      if (dst == NULL && (dst = inet_csk_route_req(sk, req)) == NULL)
            goto out;

      skb = dccp_make_response(sk, dst, req);
      if (skb != NULL) {
            const struct inet_request_sock *ireq = inet_rsk(req);
            struct dccp_hdr *dh = dccp_hdr(skb);

            dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
                                                ireq->rmt_addr);
            memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
            err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
                                  ireq->rmt_addr,
                                  ireq->opt);
            err = net_xmit_eval(err);
      }

out:
      dst_release(dst);
      return err;
}

static void dccp_v4_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
{
      int err;
      const struct iphdr *rxiph;
      struct sk_buff *skb;
      struct dst_entry *dst;

      /* Never send a reset in response to a reset. */
      if (dccp_hdr(rxskb)->dccph_type == DCCP_PKT_RESET)
            return;

      if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
            return;

      dst = dccp_v4_route_skb(dccp_v4_ctl_socket->sk, rxskb);
      if (dst == NULL)
            return;

      skb = dccp_ctl_make_reset(dccp_v4_ctl_socket, rxskb);
      if (skb == NULL)
            goto out;

      rxiph = ip_hdr(rxskb);
      dccp_hdr(skb)->dccph_checksum = dccp_v4_csum_finish(skb, rxiph->saddr,
                                                 rxiph->daddr);
      skb->dst = dst_clone(dst);

      bh_lock_sock(dccp_v4_ctl_socket->sk);
      err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
                            rxiph->daddr, rxiph->saddr, NULL);
      bh_unlock_sock(dccp_v4_ctl_socket->sk);

      if (net_xmit_eval(err) == 0) {
            DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
            DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
      }
out:
       dst_release(dst);
}

static void dccp_v4_reqsk_destructor(struct request_sock *req)
{
      kfree(inet_rsk(req)->opt);
}

static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
      .family           = PF_INET,
      .obj_size   = sizeof(struct dccp_request_sock),
      .rtx_syn_ack      = dccp_v4_send_response,
      .send_ack   = dccp_reqsk_send_ack,
      .destructor = dccp_v4_reqsk_destructor,
      .send_reset = dccp_v4_ctl_send_reset,
};

int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
{
      struct inet_request_sock *ireq;
      struct request_sock *req;
      struct dccp_request_sock *dreq;
      const __be32 service = dccp_hdr_request(skb)->dccph_req_service;
      struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);

      /* Never answer to DCCP_PKT_REQUESTs send to broadcast or multicast */
      if (((struct rtable *)skb->dst)->rt_flags &
          (RTCF_BROADCAST | RTCF_MULTICAST))
            return 0;   /* discard, don't send a reset here */

      if (dccp_bad_service_code(sk, service)) {
            dcb->dccpd_reset_code = DCCP_RESET_CODE_BAD_SERVICE_CODE;
            goto drop;
      }
      /*
       * TW buckets are converted to open requests without
       * limitations, they conserve resources and peer is
       * evidently real one.
       */
      dcb->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
      if (inet_csk_reqsk_queue_is_full(sk))
            goto drop;

      /*
       * Accept backlog is full. If we have already queued enough
       * of warm entries in syn queue, drop request. It is better than
       * clogging syn queue with openreqs with exponentially increasing
       * timeout.
       */
      if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1)
            goto drop;

      req = reqsk_alloc(&dccp_request_sock_ops);
      if (req == NULL)
            goto drop;

      if (dccp_parse_options(sk, skb))
            goto drop_and_free;

      dccp_reqsk_init(req, skb);

      if (security_inet_conn_request(sk, skb, req))
            goto drop_and_free;

      ireq = inet_rsk(req);
      ireq->loc_addr = ip_hdr(skb)->daddr;
      ireq->rmt_addr = ip_hdr(skb)->saddr;
      ireq->opt   = NULL;

      /*
       * Step 3: Process LISTEN state
       *
       * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
       *
       * In fact we defer setting S.GSR, S.SWL, S.SWH to
       * dccp_create_openreq_child.
       */
      dreq = dccp_rsk(req);
      dreq->dreq_isr       = dcb->dccpd_seq;
      dreq->dreq_iss       = dccp_v4_init_sequence(skb);
      dreq->dreq_service = service;

      if (dccp_v4_send_response(sk, req, NULL))
            goto drop_and_free;

      inet_csk_reqsk_queue_hash_add(sk, req, DCCP_TIMEOUT_INIT);
      return 0;

drop_and_free:
      reqsk_free(req);
drop:
      DCCP_INC_STATS_BH(DCCP_MIB_ATTEMPTFAILS);
      return -1;
}

EXPORT_SYMBOL_GPL(dccp_v4_conn_request);

int dccp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
{
      struct dccp_hdr *dh = dccp_hdr(skb);

      if (sk->sk_state == DCCP_OPEN) { /* Fast path */
            if (dccp_rcv_established(sk, skb, dh, skb->len))
                  goto reset;
            return 0;
      }

      /*
       *  Step 3: Process LISTEN state
       *     If P.type == Request or P contains a valid Init Cookie option,
       *          (* Must scan the packet's options to check for Init
       *           Cookies.  Only Init Cookies are processed here,
       *           however; other options are processed in Step 8.  This
       *           scan need only be performed if the endpoint uses Init
       *           Cookies *)
       *          (* Generate a new socket and switch to that socket *)
       *          Set S := new socket for this port pair
       *          S.state = RESPOND
       *          Choose S.ISS (initial seqno) or set from Init Cookies
       *          Initialize S.GAR := S.ISS
       *          Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookies
       *          Continue with S.state == RESPOND
       *          (* A Response packet will be generated in Step 11 *)
       *     Otherwise,
       *          Generate Reset(No Connection) unless P.type == Reset
       *          Drop packet and return
       *
       * NOTE: the check for the packet types is done in
       *     dccp_rcv_state_process
       */
      if (sk->sk_state == DCCP_LISTEN) {
            struct sock *nsk = dccp_v4_hnd_req(sk, skb);

            if (nsk == NULL)
                  goto discard;

            if (nsk != sk) {
                  if (dccp_child_process(sk, nsk, skb))
                        goto reset;
                  return 0;
            }
      }

      if (dccp_rcv_state_process(sk, skb, dh, skb->len))
            goto reset;
      return 0;

reset:
      dccp_v4_ctl_send_reset(sk, skb);
discard:
      kfree_skb(skb);
      return 0;
}

EXPORT_SYMBOL_GPL(dccp_v4_do_rcv);

/**
 *    dccp_invalid_packet  -  check for malformed packets
 *    Implements RFC 4340, 8.5:  Step 1: Check header basics
 *    Packets that fail these checks are ignored and do not receive Resets.
 */
int dccp_invalid_packet(struct sk_buff *skb)
{
      const struct dccp_hdr *dh;
      unsigned int cscov;

      if (skb->pkt_type != PACKET_HOST)
            return 1;

      /* If the packet is shorter than 12 bytes, drop packet and return */
      if (!pskb_may_pull(skb, sizeof(struct dccp_hdr))) {
            DCCP_WARN("pskb_may_pull failed\n");
            return 1;
      }

      dh = dccp_hdr(skb);

      /* If P.type is not understood, drop packet and return */
      if (dh->dccph_type >= DCCP_PKT_INVALID) {
            DCCP_WARN("invalid packet type\n");
            return 1;
      }

      /*
       * If P.Data Offset is too small for packet type, drop packet and return
       */
      if (dh->dccph_doff < dccp_hdr_len(skb) / sizeof(u32)) {
            DCCP_WARN("P.Data Offset(%u) too small\n", dh->dccph_doff);
            return 1;
      }
      /*
       * If P.Data Offset is too too large for packet, drop packet and return
       */
      if (!pskb_may_pull(skb, dh->dccph_doff * sizeof(u32))) {
            DCCP_WARN("P.Data Offset(%u) too large\n", dh->dccph_doff);
            return 1;
      }

      /*
       * If P.type is not Data, Ack, or DataAck and P.X == 0 (the packet
       * has short sequence numbers), drop packet and return
       */
      if (dh->dccph_type >= DCCP_PKT_DATA    &&
          dh->dccph_type <= DCCP_PKT_DATAACK && dh->dccph_x == 0)  {
            DCCP_WARN("P.type (%s) not Data || [Data]Ack, while P.X == 0\n",
                    dccp_packet_name(dh->dccph_type));
            return 1;
      }

      /*
       * If P.CsCov is too large for the packet size, drop packet and return.
       * This must come _before_ checksumming (not as RFC 4340 suggests).
       */
      cscov = dccp_csum_coverage(skb);
      if (cscov > skb->len) {
            DCCP_WARN("P.CsCov %u exceeds packet length %d\n",
                    dh->dccph_cscov, skb->len);
            return 1;
      }

      /* If header checksum is incorrect, drop packet and return.
       * (This step is completed in the AF-dependent functions.) */
      skb->csum = skb_checksum(skb, 0, cscov, 0);

      return 0;
}

EXPORT_SYMBOL_GPL(dccp_invalid_packet);

/* this is called when real data arrives */
static int dccp_v4_rcv(struct sk_buff *skb)
{
      const struct dccp_hdr *dh;
      const struct iphdr *iph;
      struct sock *sk;
      int min_cov;

      /* Step 1: Check header basics */

      if (dccp_invalid_packet(skb))
            goto discard_it;

      iph = ip_hdr(skb);
      /* Step 1: If header checksum is incorrect, drop packet and return */
      if (dccp_v4_csum_finish(skb, iph->saddr, iph->daddr)) {
            DCCP_WARN("dropped packet with invalid checksum\n");
            goto discard_it;
      }

      dh = dccp_hdr(skb);

      DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
      DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;

      dccp_pr_debug("%8.8s "
                  "src=%u.%u.%u.%u@%-5d "
                  "dst=%u.%u.%u.%u@%-5d seq=%llu",
                  dccp_packet_name(dh->dccph_type),
                  NIPQUAD(iph->saddr), ntohs(dh->dccph_sport),
                  NIPQUAD(iph->daddr), ntohs(dh->dccph_dport),
                  (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);

      if (dccp_packet_without_ack(skb)) {
            DCCP_SKB_CB(skb)->dccpd_ack_seq = DCCP_PKT_WITHOUT_ACK_SEQ;
            dccp_pr_debug_cat("\n");
      } else {
            DCCP_SKB_CB(skb)->dccpd_ack_seq = dccp_hdr_ack_seq(skb);
            dccp_pr_debug_cat(", ack=%llu\n", (unsigned long long)
                          DCCP_SKB_CB(skb)->dccpd_ack_seq);
      }

      /* Step 2:
       *    Look up flow ID in table and get corresponding socket */
      sk = __inet_lookup(&dccp_hashinfo,
                     iph->saddr, dh->dccph_sport,
                     iph->daddr, dh->dccph_dport, inet_iif(skb));
      /*
       * Step 2:
       *    If no socket ...
       */
      if (sk == NULL) {
            dccp_pr_debug("failed to look up flow ID in table and "
                        "get corresponding socket\n");
            goto no_dccp_socket;
      }

      /*
       * Step 2:
       *    ... or S.state == TIMEWAIT,
       *          Generate Reset(No Connection) unless P.type == Reset
       *          Drop packet and return
       */
      if (sk->sk_state == DCCP_TIME_WAIT) {
            dccp_pr_debug("sk->sk_state == DCCP_TIME_WAIT: do_time_wait\n");
            inet_twsk_put(inet_twsk(sk));
            goto no_dccp_socket;
      }

      /*
       * RFC 4340, sec. 9.2.1: Minimum Checksum Coverage
       *    o if MinCsCov = 0, only packets with CsCov = 0 are accepted
       *    o if MinCsCov > 0, also accept packets with CsCov >= MinCsCov
       */
      min_cov = dccp_sk(sk)->dccps_pcrlen;
      if (dh->dccph_cscov && (min_cov == 0 || dh->dccph_cscov < min_cov))  {
            dccp_pr_debug("Packet CsCov %d does not satisfy MinCsCov %d\n",
                        dh->dccph_cscov, min_cov);
            /* FIXME: "Such packets SHOULD be reported using Data Dropped
             *         options (Section 11.7) with Drop Code 0, Protocol
             *         Constraints."                                     */
            goto discard_and_relse;
      }

      if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
            goto discard_and_relse;
      nf_reset(skb);

      return sk_receive_skb(sk, skb, 1);

no_dccp_socket:
      if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
            goto discard_it;
      /*
       * Step 2:
       *    If no socket ...
       *          Generate Reset(No Connection) unless P.type == Reset
       *          Drop packet and return
       */
      if (dh->dccph_type != DCCP_PKT_RESET) {
            DCCP_SKB_CB(skb)->dccpd_reset_code =
                              DCCP_RESET_CODE_NO_CONNECTION;
            dccp_v4_ctl_send_reset(sk, skb);
      }

discard_it:
      kfree_skb(skb);
      return 0;

discard_and_relse:
      sock_put(sk);
      goto discard_it;
}

static struct inet_connection_sock_af_ops dccp_ipv4_af_ops = {
      .queue_xmit    = ip_queue_xmit,
      .send_check    = dccp_v4_send_check,
      .rebuild_header      = inet_sk_rebuild_header,
      .conn_request        = dccp_v4_conn_request,
      .syn_recv_sock       = dccp_v4_request_recv_sock,
      .net_header_len      = sizeof(struct iphdr),
      .setsockopt    = ip_setsockopt,
      .getsockopt    = ip_getsockopt,
      .addr2sockaddr       = inet_csk_addr2sockaddr,
      .sockaddr_len        = sizeof(struct sockaddr_in),
#ifdef CONFIG_COMPAT
      .compat_setsockopt = compat_ip_setsockopt,
      .compat_getsockopt = compat_ip_getsockopt,
#endif
};

static int dccp_v4_init_sock(struct sock *sk)
{
      static __u8 dccp_v4_ctl_sock_initialized;
      int err = dccp_init_sock(sk, dccp_v4_ctl_sock_initialized);

      if (err == 0) {
            if (unlikely(!dccp_v4_ctl_sock_initialized))
                  dccp_v4_ctl_sock_initialized = 1;
            inet_csk(sk)->icsk_af_ops = &dccp_ipv4_af_ops;
      }

      return err;
}

static struct timewait_sock_ops dccp_timewait_sock_ops = {
      .twsk_obj_size    = sizeof(struct inet_timewait_sock),
};

DEFINE_PROTO_INUSE(dccp_v4)

static struct proto dccp_v4_prot = {
      .name             = "DCCP",
      .owner                  = THIS_MODULE,
      .close                  = dccp_close,
      .connect          = dccp_v4_connect,
      .disconnect       = dccp_disconnect,
      .ioctl                  = dccp_ioctl,
      .init             = dccp_v4_init_sock,
      .setsockopt       = dccp_setsockopt,
      .getsockopt       = dccp_getsockopt,
      .sendmsg          = dccp_sendmsg,
      .recvmsg          = dccp_recvmsg,
      .backlog_rcv            = dccp_v4_do_rcv,
      .hash             = dccp_hash,
      .unhash                 = dccp_unhash,
      .accept                 = inet_csk_accept,
      .get_port         = dccp_v4_get_port,
      .shutdown         = dccp_shutdown,
      .destroy          = dccp_destroy_sock,
      .orphan_count           = &dccp_orphan_count,
      .max_header       = MAX_DCCP_HEADER,
      .obj_size         = sizeof(struct dccp_sock),
      .rsk_prot         = &dccp_request_sock_ops,
      .twsk_prot        = &dccp_timewait_sock_ops,
#ifdef CONFIG_COMPAT
      .compat_setsockopt      = compat_dccp_setsockopt,
      .compat_getsockopt      = compat_dccp_getsockopt,
#endif
      REF_PROTO_INUSE(dccp_v4)
};

static struct net_protocol dccp_v4_protocol = {
      .handler    = dccp_v4_rcv,
      .err_handler      = dccp_v4_err,
      .no_policy  = 1,
};

static const struct proto_ops inet_dccp_ops = {
      .family              = PF_INET,
      .owner               = THIS_MODULE,
      .release       = inet_release,
      .bind          = inet_bind,
      .connect       = inet_stream_connect,
      .socketpair    = sock_no_socketpair,
      .accept              = inet_accept,
      .getname       = inet_getname,
      /* FIXME: work on tcp_poll to rename it to inet_csk_poll */
      .poll          = dccp_poll,
      .ioctl               = inet_ioctl,
      /* FIXME: work on inet_listen to rename it to sock_common_listen */
      .listen              = inet_dccp_listen,
      .shutdown      = inet_shutdown,
      .setsockopt    = sock_common_setsockopt,
      .getsockopt    = sock_common_getsockopt,
      .sendmsg       = inet_sendmsg,
      .recvmsg       = sock_common_recvmsg,
      .mmap          = sock_no_mmap,
      .sendpage      = sock_no_sendpage,
#ifdef CONFIG_COMPAT
      .compat_setsockopt = compat_sock_common_setsockopt,
      .compat_getsockopt = compat_sock_common_getsockopt,
#endif
};

static struct inet_protosw dccp_v4_protosw = {
      .type       = SOCK_DCCP,
      .protocol   = IPPROTO_DCCP,
      .prot       = &dccp_v4_prot,
      .ops        = &inet_dccp_ops,
      .capability = -1,
      .no_check   = 0,
      .flags            = INET_PROTOSW_ICSK,
};

static int __init dccp_v4_init(void)
{
      int err = proto_register(&dccp_v4_prot, 1);

      if (err != 0)
            goto out;

      err = inet_add_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
      if (err != 0)
            goto out_proto_unregister;

      inet_register_protosw(&dccp_v4_protosw);

      err = inet_csk_ctl_sock_create(&dccp_v4_ctl_socket, PF_INET,
                               SOCK_DCCP, IPPROTO_DCCP);
      if (err)
            goto out_unregister_protosw;
out:
      return err;
out_unregister_protosw:
      inet_unregister_protosw(&dccp_v4_protosw);
      inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
out_proto_unregister:
      proto_unregister(&dccp_v4_prot);
      goto out;
}

static void __exit dccp_v4_exit(void)
{
      inet_unregister_protosw(&dccp_v4_protosw);
      inet_del_protocol(&dccp_v4_protocol, IPPROTO_DCCP);
      proto_unregister(&dccp_v4_prot);
}

module_init(dccp_v4_init);
module_exit(dccp_v4_exit);

/*
 * __stringify doesn't likes enums, so use SOCK_DCCP (6) and IPPROTO_DCCP (33)
 * values directly, Also cover the case where the protocol is not specified,
 * i.e. net-pf-PF_INET-proto-0-type-SOCK_DCCP
 */
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 33, 6);
MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 0, 6);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arnaldo Carvalho de Melo <acme@mandriva.com>");
MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");

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