ipv4.c

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/*
 *  net/dccp/ipv4.c
 *
 *  An implementation of the DCCP protocol
 *  Arnaldo Carvalho de Melo <[email protected]>
 *
 *  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/slab.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 <net/secure_seq.h>

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

/*
 * The per-net dccp.v4_ctl_sk socket is used for responding to
 * the Out-of-the-blue (OOTB) packets. A control sock will be created
 * for this socket at the initialization time.
 */

int dccp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
    const struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
    struct inet_sock *inet = inet_sk(sk);
    struct dccp_sock *dp = dccp_sk(sk);
    __be16 orig_sport, orig_dport;
    __be32 daddr, nexthop;
    struct flowi4 *fl4;
    struct rtable *rt;
    int err;
    struct ip_options_rcu *inet_opt;

    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;

    inet_opt = rcu_dereference_protected(inet->inet_opt,
                         sock_owned_by_user(sk));
    if (inet_opt != NULL && inet_opt->opt.srr) {
        if (daddr == 0)
            return -EINVAL;
        nexthop = inet_opt->opt.faddr;
    }

    orig_sport = inet->inet_sport;
    orig_dport = usin->sin_port;
    fl4 = &inet->cork.fl.u.ip4;
    rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
                  RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
                  IPPROTO_DCCP,
                  orig_sport, orig_dport, sk, true);
    if (IS_ERR(rt))
        return PTR_ERR(rt);

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

    if (inet_opt == NULL || !inet_opt->opt.srr)
        daddr = fl4->daddr;

    if (inet->inet_saddr == 0)
        inet->inet_saddr = fl4->saddr;
    inet->inet_rcv_saddr = inet->inet_saddr;

    inet->inet_dport = usin->sin_port;
    inet->inet_daddr = daddr;

    inet_csk(sk)->icsk_ext_hdr_len = 0;
    if (inet_opt)
        inet_csk(sk)->icsk_ext_hdr_len = inet_opt->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;

    rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
                   inet->inet_sport, inet->inet_dport, sk);
    if (IS_ERR(rt)) {
        err = PTR_ERR(rt);
        rt = NULL;
        goto failure;
    }
    /* OK, now commit destination to socket.  */
    sk_setup_caps(sk, &rt->dst);

    dp->dccps_iss = secure_dccp_sequence_number(inet->inet_saddr,
                            inet->inet_daddr,
                            inet->inet_sport,
                            inet->inet_dport);
    inet->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->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;

    dst = inet_csk_update_pmtu(sk, mtu);
    if (!dst)
        return;

    /* 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 */
}

static void dccp_do_redirect(struct sk_buff *skb, struct sock *sk)
{
    struct dst_entry *dst = __sk_dst_check(sk, 0);

    if (dst)
        dst->ops->redirect(dst, sk, skb);
}

/*
 * 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 u8 offset = iph->ihl << 2;
    const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
    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;
    struct net *net = dev_net(skb->dev);

    if (skb->len < offset + sizeof(*dh) ||
        skb->len < offset + __dccp_basic_hdr_len(dh)) {
        ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
        return;
    }

    sk = inet_lookup(net, &dccp_hashinfo,
            iph->daddr, dh->dccph_dport,
            iph->saddr, dh->dccph_sport, inet_iif(skb));
    if (sk == NULL) {
        ICMP_INC_STATS_BH(net, 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(net, 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_awl, dp->dccps_awh)) {
        NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
        goto out;
    }

    switch (type) {
    case ICMP_REDIRECT:
        dccp_do_redirect(skb, sk);
        goto out;
    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.
         */
        WARN_ON(req->sk);

        if (!between48(seq, dccp_rsk(req)->dreq_iss,
                    dccp_rsk(req)->dreq_gss)) {
            NET_INC_STATS_BH(net, 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, 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->inet_saddr,
                         inet->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;

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

    newinet        = inet_sk(newsk);
    ireq           = inet_rsk(req);
    newinet->inet_daddr = ireq->rmt_addr;
    newinet->inet_rcv_saddr = ireq->loc_addr;
    newinet->inet_saddr = ireq->loc_addr;
    newinet->inet_opt   = ireq->opt;
    ireq->opt      = NULL;
    newinet->mc_index  = inet_iif(skb);
    newinet->mc_ttl    = ip_hdr(skb)->ttl;
    newinet->inet_id   = jiffies;

    if (dst == NULL && (dst = inet_csk_route_child_sock(sk, newsk, req)) == NULL)
        goto put_and_exit;

    sk_setup_caps(newsk, dst);

    dccp_sync_mss(newsk, dst_mtu(dst));

    if (__inet_inherit_port(sk, newsk) < 0)
        goto put_and_exit;
    __inet_hash_nolisten(newsk, NULL);

    return newsk;

exit_overflow:
    NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
exit_nonewsk:
    dst_release(dst);
exit:
    NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
    return NULL;
put_and_exit:
    bh_unlock_sock(newsk);
    sock_put(newsk);
    goto exit;
}

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(sock_net(sk), &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 net *net, struct sock *sk,
                       struct sk_buff *skb)
{
    struct rtable *rt;
    const struct iphdr *iph = ip_hdr(skb);
    struct flowi4 fl4 = {
        .flowi4_oif = inet_iif(skb),
        .daddr = iph->saddr,
        .saddr = iph->daddr,
        .flowi4_tos = RT_CONN_FLAGS(sk),
        .flowi4_proto = sk->sk_protocol,
        .fl4_sport = dccp_hdr(skb)->dccph_dport,
        .fl4_dport = dccp_hdr(skb)->dccph_sport,
    };

    security_skb_classify_flow(skb, flowi4_to_flowi(&fl4));
    rt = ip_route_output_flow(net, &fl4, sk);
    if (IS_ERR(rt)) {
        IP_INC_STATS_BH(net, IPSTATS_MIB_OUTNOROUTES);
        return NULL;
    }

    return &rt->dst;
}

static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
                 struct request_values *rv_unused)
{
    int err = -1;
    struct sk_buff *skb;
    struct dst_entry *dst;
    struct flowi4 fl4;

    dst = inet_csk_route_req(sk, &fl4, req);
    if (dst == 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);
        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;
    struct net *net = dev_net(skb_dst(rxskb)->dev);
    struct sock *ctl_sk = net->dccp.v4_ctl_sk;

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

    if (skb_rtable(rxskb)->rt_type != RTN_LOCAL)
        return;

    dst = dccp_v4_route_skb(net, ctl_sk, rxskb);
    if (dst == NULL)
        return;

    skb = dccp_ctl_make_reset(ctl_sk, 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_set(skb, dst_clone(dst));

    bh_lock_sock(ctl_sk);
    err = ip_build_and_send_pkt(skb, ctl_sk,
                    rxiph->daddr, rxiph->saddr, NULL);
    bh_unlock_sock(ctl_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)
{
    dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
    kfree(inet_rsk(req)->opt);
}

void dccp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
{
}
EXPORT_SYMBOL(dccp_syn_ack_timeout);

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,
    .syn_ack_timeout = dccp_syn_ack_timeout,
};

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 (skb_rtable(skb)->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 = inet_reqsk_alloc(&dccp_request_sock_ops);
    if (req == NULL)
        goto drop;

    if (dccp_reqsk_init(req, dccp_sk(sk), skb))
        goto drop_and_free;

    dreq = dccp_rsk(req);
    if (dccp_parse_options(sk, dreq, skb))
        goto drop_and_free;

    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;

    /*
     * Step 3: Process LISTEN state
     *
     * Set S.ISR, S.GSR, S.SWL, S.SWH from packet or Init Cookie
     *
     * Setting S.SWL/S.SWH to is deferred to dccp_create_openreq_child().
     */
    dreq->dreq_isr     = dcb->dccpd_seq;
    dreq->dreq_gsr     = dreq->dreq_isr;
    dreq->dreq_iss     = dccp_v4_init_sequence(skb);
    dreq->dreq_gss     = dreq->dreq_iss;
    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);

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=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
              dccp_packet_name(dh->dccph_type),
              &iph->saddr, ntohs(dh->dccph_sport),
              &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_skb(&dccp_hashinfo, skb,
                   dh->dccph_sport, dh->dccph_dport);
    /*
     * 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 const 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),
    .bind_conflict     = inet_csk_bind_conflict,
#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),
};

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           = inet_hash,
    .unhash         = inet_unhash,
    .accept         = inet_csk_accept,
    .get_port       = inet_csk_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),
    .slab_flags     = SLAB_DESTROY_BY_RCU,
    .rsk_prot       = &dccp_request_sock_ops,
    .twsk_prot      = &dccp_timewait_sock_ops,
    .h.hashinfo     = &dccp_hashinfo,
#ifdef CONFIG_COMPAT
    .compat_setsockopt  = compat_dccp_setsockopt,
    .compat_getsockopt  = compat_dccp_getsockopt,
#endif
};

static const struct net_protocol dccp_v4_protocol = {
    .handler    = dccp_v4_rcv,
    .err_handler    = dccp_v4_err,
    .no_policy  = 1,
    .netns_ok   = 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,
    .no_check   = 0,
    .flags      = INET_PROTOSW_ICSK,
};

static int __net_init dccp_v4_init_net(struct net *net)
{
    if (dccp_hashinfo.bhash == NULL)
        return -ESOCKTNOSUPPORT;

    return inet_ctl_sock_create(&net->dccp.v4_ctl_sk, PF_INET,
                    SOCK_DCCP, IPPROTO_DCCP, net);
}

static void __net_exit dccp_v4_exit_net(struct net *net)
{
    inet_ctl_sock_destroy(net->dccp.v4_ctl_sk);
}

static struct pernet_operations dccp_v4_ops = {
    .init   = dccp_v4_init_net,
    .exit   = dccp_v4_exit_net,
};

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 = register_pernet_subsys(&dccp_v4_ops);
    if (err)
        goto out_destroy_ctl_sock;
out:
    return err;
out_destroy_ctl_sock:
    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)
{
    unregister_pernet_subsys(&dccp_v4_ops);
    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 <[email protected]>");
MODULE_DESCRIPTION("DCCP - Datagram Congestion Controlled Protocol");