test

/* *    Connect to a remote host. There is regrettably still a little *    TCP 'magic' in here. */int inet_stream_connect(struct socket *sock, struct sockaddr *uaddr,            int addr_len, int flags){    struct sock *sk = sock->sk;    int err;    long timeo;    lock_sock(sk);    if (uaddr->sa_family == AF_UNSPEC) {        err = sk->sk_prot->disconnect(sk, flags);        sock->state = err ? SS_DISCONNECTING : SS_UNCONNECTED;        goto out;    }    switch (sock->state) {    default:        err = -EINVAL;        goto out;    case SS_CONNECTED:        err = -EISCONN;        goto out;    case SS_CONNECTING:        err = -EALREADY;        /* Fall out of switch with err, set for this state */        break;    /* sock->state在inet_create时被设置为SS_UNCONNECTED */    case SS_UNCONNECTED:        err = -EISCONN;        /* 在inet_create中调用的sock_init_data函数中sk->sk_state被初始化为TCP_CLOSE */        /* 在inet_create中sk->sk_prot->init中同样会被初始化为TCP_CLOSE，init对应了tcp_v4_init_sock函数，初始化的动作重复了 */                if (sk->sk_state != TCP_CLOSE)            goto out;        /* 对应tcp_prot.connect，即tcp_v4_connect */        err = sk->sk_prot->connect(sk, uaddr, addr_len);        if (err < 0)            goto out;                /× 更新当前状态为SS_CONNECTING ×/        sock->state = SS_CONNECTING;        /* Just entered SS_CONNECTING state; the only         * difference is that return value in non-blocking         * case is EINPROGRESS, rather than EALREADY.         */        err = -EINPROGRESS;        break;    }       timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);    if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {        /* Error code is set above */        if (!timeo || !inet_wait_for_connect(sk, timeo))            goto out;        err = sock_intr_errno(timeo);        if (signal_pending(current))            goto out;    }    /* Connection was closed by RST, timeout, ICMP error     * or another process disconnected us.     */    if (sk->sk_state == TCP_CLOSE)        goto sock_error;    /* sk->sk_err may be not zero now, if RECVERR was ordered by user     * and error was received after socket entered established state.     * Hence, it is handled normally after connect() return successfully.     */    sock->state = SS_CONNECTED;    err = 0;out:    release_sock(sk);    return err;sock_error:    err = sock_error(sk) ? : -ECONNABORTED;    sock->state = SS_UNCONNECTED;    if (sk->sk_prot->disconnect(sk, flags))        sock->state = SS_DISCONNECTING;    goto out;

/* This will initiate an outgoing connection. */int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len){    struct inet_sock *inet = inet_sk(sk);    struct tcp_sock *tp = tcp_sk(sk);    struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;    struct rtable *rt;    __be32 daddr, nexthop;    int tmp;    int err;    struct ip_options *inet_opt;        /* 检查一下地址长度和协议族类型 */    if (addr_len < sizeof(struct sockaddr_in))        return -EINVAL;    if (usin->sin_family != AF_INET)        return -EAFNOSUPPORT;    /× 将nexthop和daddr暂时初始化为目标地址 ×/    nexthop = daddr = usin->sin_addr.s_addr;    inet_opt = rcu_dereference(inet->opt);    /× 如果指定了源路由选项,则按照指定的下一跳进行处理 ×/    if (inet_opt && inet_opt->srr) {        if (!daddr)            return -EINVAL;        nexthop = inet_opt->faddr;    }    /× 本地发包需要确认源IP地址和源端口，如果没有提供源IP地址会通过路由查找过程中的inet_select_addr来选择源地址 ×/    /× 路由查找成功后会生成路由缓存项，可以加速后续报文的发送，下面函数返回路由缓存项，包含源IP地址 ×/    tmp = ip_route_connect(&rt, nexthop, inet->saddr,             RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,             IPPROTO_TCP,             inet->sport, usin->sin_port, sk, 1);    if (tmp < 0) {        if (tmp == -ENETUNREACH)            IP_INC_STATS_BH(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);        return tmp;    }    /× 正常TCP连接查找到的都是单播路由 ×/    if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {        ip_rt_put(rt);        return -ENETUNREACH;    }    /* 使用查完路由后的目的地址更新临时daddr,有可能与用户传入的目的地址不同 */    if (!inet_opt || !inet_opt->srr)        daddr = rt->rt_dst;    /* 如果没有指定源地址,则使用路由选择的源地址 */    if (!inet->saddr)        inet->saddr = rt->rt_src;    inet->rcv_saddr = inet->saddr;        if (tp->rx_opt.ts_recent_stamp && inet->daddr != daddr) {        /* Reset inherited state */        tp->rx_opt.ts_recent     = 0;        tp->rx_opt.ts_recent_stamp = 0;        tp->write_seq         = 0;    }    if (tcp_death_row.sysctl_tw_recycle &&     !tp->rx_opt.ts_recent_stamp && rt->rt_dst == daddr) {        struct inet_peer *peer = rt_get_peer(rt);        /*         * VJ's idea. We save last timestamp seen from         * the destination in peer table, when entering state         * TIME-WAIT * and initialize rx_opt.ts_recent from it,         * when trying new connection.         */        if (peer != NULL &&         peer->tcp_ts_stamp + TCP_PAWS_MSL >= get_seconds()) {            tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;            tp->rx_opt.ts_recent = peer->tcp_ts;        }    }    /* 记录目的端口和目的IP */    inet->dport = usin->sin_port;    inet->daddr = daddr;    /× 设置IP选项的长度 ×/    inet_csk(sk)->icsk_ext_hdr_len = 0;    if (inet_opt)        inet_csk(sk)->icsk_ext_hdr_len = inet_opt->optlen;    /× 允许的最小MSS ×/    tp->rx_opt.mss_clamp = 536;    /* Socket identity is still unknown (sport may be zero).     * However we set state to SYN-SENT and not releasing socket     * lock select source port, enter ourselves into the hash tables and     * complete initialization after this.     */    /× 马上要发送SYN了，所以可以更新sk->sk_state状态值了 ×/    tcp_set_state(sk, TCP_SYN_SENT);    /× 进行端口选择，并与sk绑定，下面会重点分析一下 ×/    err = inet_hash_connect(&tcp_death_row, sk);    if (err)        goto failure;    /×  使用sport更新路由缓存表 ×/    err = ip_route_newports(&rt, IPPROTO_TCP,                inet->sport, inet->dport, sk);    if (err)        goto failure;    /* OK, now commit destination to socket. */    /× 更新sock的路由缓存项，设置gso标签 ×/    sk->sk_gso_type = SKB_GSO_TCPV4;    sk_setup_caps(sk, &rt->u.dst);        /× 计算发送第一个报文的初始化序列号 ×/    if (!tp->write_seq)        tp->write_seq = secure_tcp_sequence_number(inet->saddr,                             inet->daddr,                             inet->sport,                             usin->sin_port);    /× 计算IP报文ID ×/    inet->id = tp->write_seq ^ jiffies;    /× 发送SYN报文 ×/     err = tcp_connect(sk);    rt = NULL;    if (err)        goto failure;    return 0;failure:    /*     * This unhashes the socket and releases the local port,     * if necessary.     */    tcp_set_state(sk, TCP_CLOSE);    ip_rt_put(rt);    sk->sk_route_caps = 0;    inet->dport = 0;    return err;}

/* This will initiate an outgoing connection. */int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len){    struct inet_sock *inet = inet_sk(sk);    struct tcp_sock *tp = tcp_sk(sk);    struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;    struct rtable *rt;    __be32 daddr, nexthop;    int tmp;    int err;    struct ip_options *inet_opt;        /* 检查一下地址长度和协议族类型 */    if (addr_len < sizeof(struct sockaddr_in))        return -EINVAL;    if (usin->sin_family != AF_INET)        return -EAFNOSUPPORT;    /* 将nexthop和daddr暂时初始化为目标地址 */    nexthop = daddr = usin->sin_addr.s_addr;    inet_opt = rcu_dereference(inet->opt);    /* 如果指定了源路由选项,则按照指定的下一跳进行处理 */    if (inet_opt && inet_opt->srr) {        if (!daddr)            return -EINVAL;        nexthop = inet_opt->faddr;    }    /* 本地发包需要确认源IP地址和源端口，如果没有提供源IP地址会通过路由查找过程中的inet_select_addr来选择源地址 */    /* 路由查找成功后会生成路由缓存项，可以加速后续报文的发送，下面函数返回路由缓存项，包含源IP地址 */    tmp = ip_route_connect(&rt, nexthop, inet->saddr,             RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,             IPPROTO_TCP,             inet->sport, usin->sin_port, sk, 1);    if (tmp < 0) {        if (tmp == -ENETUNREACH)            IP_INC_STATS_BH(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);        return tmp;    }    /* 正常TCP连接查找到的都是单播路由 */    if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {        ip_rt_put(rt);        return -ENETUNREACH;    }    /* 使用查完路由后的目的地址更新临时daddr,有可能与用户传入的目的地址不同 */    if (!inet_opt || !inet_opt->srr)        daddr = rt->rt_dst;    /* 如果没有指定源地址,则使用路由选择的源地址 */    if (!inet->saddr)        inet->saddr = rt->rt_src;    inet->rcv_saddr = inet->saddr;        if (tp->rx_opt.ts_recent_stamp && inet->daddr != daddr) {        /* Reset inherited state */        tp->rx_opt.ts_recent     = 0;        tp->rx_opt.ts_recent_stamp = 0;        tp->write_seq         = 0;    }    if (tcp_death_row.sysctl_tw_recycle &&     !tp->rx_opt.ts_recent_stamp && rt->rt_dst == daddr) {        struct inet_peer *peer = rt_get_peer(rt);        /*         * VJ's idea. We save last timestamp seen from         * the destination in peer table, when entering state         * TIME-WAIT * and initialize rx_opt.ts_recent from it,         * when trying new connection.         */        if (peer != NULL &&         peer->tcp_ts_stamp + TCP_PAWS_MSL >= get_seconds()) {            tp->rx_opt.ts_recent_stamp = peer->tcp_ts_stamp;            tp->rx_opt.ts_recent = peer->tcp_ts;        }    }    /* 记录目的端口和目的IP */    inet->dport = usin->sin_port;    inet->daddr = daddr;    /* 设置IP选项的长度 */    inet_csk(sk)->icsk_ext_hdr_len = 0;    if (inet_opt)        inet_csk(sk)->icsk_ext_hdr_len = inet_opt->optlen;    /* 允许的最小MSS */    tp->rx_opt.mss_clamp = 536;    /* Socket identity is still unknown (sport may be zero).     * However we set state to SYN-SENT and not releasing socket     * lock select source port, enter ourselves into the hash tables and     * complete initialization after this.     */    /* 马上要发送SYN了，所以可以更新sk->sk_state状态值了 */    tcp_set_state(sk, TCP_SYN_SENT);    /* 进行端口选择，并与sk绑定，下面会重点分析一下 */    err = inet_hash_connect(&tcp_death_row, sk);    if (err)        goto failure;    /*  使用sport更新路由缓存表 */    err = ip_route_newports(&rt, IPPROTO_TCP,                inet->sport, inet->dport, sk);    if (err)        goto failure;    /* OK, now commit destination to socket. */    /* 更新sock的路由缓存项，设置gso标签 */    sk->sk_gso_type = SKB_GSO_TCPV4;    sk_setup_caps(sk, &rt->u.dst);        /* 计算发送第一个报文的初始化序列号 */    if (!tp->write_seq)        tp->write_seq = secure_tcp_sequence_number(inet->saddr,                             inet->daddr,                             inet->sport,                             usin->sin_port);    /* 计算IP报文ID */    inet->id = tp->write_seq ^ jiffies;    /* 发送SYN报文 */     err = tcp_connect(sk);    rt = NULL;    if (err)        goto failure;    return 0;failure:    /*     * This unhashes the socket and releases the local port,     * if necessary.     */    tcp_set_state(sk, TCP_CLOSE);    ip_rt_put(rt);    sk->sk_route_caps = 0;    inet->dport = 0;    return err;}