src/openvpn/socket.h

/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2022 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program 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.
 */

#ifndef SOCKET_H
#define SOCKET_H

#include "buffer.h"
#include "common.h"
#include "error.h"
#include "proto.h"
#include "mtu.h"
#include "win32.h"
#include "event.h"
#include "proxy.h"
#include "socks.h"
#include "misc.h"

/*
 * OpenVPN's default port number as assigned by IANA.
 */
#define OPENVPN_PORT "1194"

/*
 * Number of seconds that "resolv-retry infinite"
 * represents.
 */
#define RESOLV_RETRY_INFINITE 1000000000

/*
 * packet_size_type is used to communicate packet size
 * over the wire when stream oriented protocols are
 * being used
 */

typedef uint16_t packet_size_type;

/* convert a packet_size_type from host to network order */
#define htonps(x) htons(x)

/* convert a packet_size_type from network to host order */
#define ntohps(x) ntohs(x)

/* OpenVPN sockaddr struct */
struct openvpn_sockaddr
{
    /*int dummy;*/ /* add offset to force a bug if sa not explicitly dereferenced */
    union {
        struct sockaddr sa;
        struct sockaddr_in in4;
        struct sockaddr_in6 in6;
    } addr;
};

/* struct to hold preresolved host names */
struct cached_dns_entry {
    const char *hostname;
    const char *servname;
    int ai_family;
    int flags;
    struct addrinfo *ai;
    struct cached_dns_entry *next;
};

/* actual address of remote, based on source address of received packets */
struct link_socket_actual
{
    /*int dummy;*/ /* add offset to force a bug if dest not explicitly dereferenced */

    struct openvpn_sockaddr dest;
#if ENABLE_IP_PKTINFO
    union {
#if defined(HAVE_IN_PKTINFO) && defined(HAVE_IPI_SPEC_DST)
        struct in_pktinfo in4;
#elif defined(IP_RECVDSTADDR)
        struct in_addr in4;
#endif
        struct in6_pktinfo in6;
    } pi;
#endif
};

/* IP addresses which are persistent across SIGUSR1s */
struct link_socket_addr
{
    struct addrinfo *bind_local;
    struct addrinfo *remote_list; /* complete remote list */
    struct addrinfo *current_remote; /* remote used in the
                                      * current connection attempt */
    struct link_socket_actual actual; /* reply to this address */
};

struct link_socket_info
{
    struct link_socket_addr *lsa;
    bool connection_established;
    const char *ipchange_command;
    const struct plugin_list *plugins;
    bool remote_float;
    int proto;                  /* Protocol (PROTO_x defined below) */
    sa_family_t af;                     /* Address family like AF_INET, AF_INET6 or AF_UNSPEC*/
    bool bind_ipv6_only;
    int mtu_changed;            /* Set to true when mtu value is changed */
};

/*
 * Used to extract packets encapsulated in streams into a buffer,
 * in this case IP packets embedded in a TCP stream.
 */
struct stream_buf
{
    struct buffer buf_init;
    struct buffer residual;
    int maxlen;
    bool residual_fully_formed;

    struct buffer buf;
    struct buffer next;
    int len;   /* -1 if not yet known */

    bool error; /* if true, fatal TCP error has occurred,
                 *  requiring that connection be restarted */
#if PORT_SHARE
#define PS_DISABLED 0
#define PS_ENABLED  1
#define PS_FOREIGN  2
    int port_share_state;
#endif
};

/*
 * Used to set socket buffer sizes
 */
struct socket_buffer_size
{
    int rcvbuf;
    int sndbuf;
};

/*
 * This is the main socket structure used by OpenVPN.  The SOCKET_
 * defines try to abstract away our implementation differences between
 * using sockets on Posix vs. Win32.
 */
struct link_socket
{
    struct link_socket_info info;

    socket_descriptor_t sd;
    socket_descriptor_t ctrl_sd; /* only used for UDP over Socks */

#ifdef _WIN32
    struct overlapped_io reads;
    struct overlapped_io writes;
    struct rw_handle rw_handle;
    struct rw_handle listen_handle; /* For listening on TCP socket in server mode */
#endif

    /* used for printing status info only */
    unsigned int rwflags_debug;

    /* used for long-term queueing of pre-accepted socket listen */
    bool listen_persistent_queued;

    const char *remote_host;
    const char *remote_port;
    const char *local_host;
    const char *local_port;
    struct cached_dns_entry *dns_cache;
    bool bind_local;

#define INETD_NONE   0
#define INETD_WAIT   1
#define INETD_NOWAIT 2
    int inetd;

#define LS_MODE_DEFAULT           0
#define LS_MODE_TCP_LISTEN        1
#define LS_MODE_TCP_ACCEPT_FROM   2
    int mode;

    int resolve_retry_seconds;
    int mtu_discover_type;

    struct socket_buffer_size socket_buffer_sizes;

    int mtu;                    /* OS discovered MTU, or 0 if unknown */

#define SF_USE_IP_PKTINFO (1<<0)
#define SF_TCP_NODELAY (1<<1)
#define SF_PORT_SHARE (1<<2)
#define SF_HOST_RANDOMIZE (1<<3)
#define SF_GETADDRINFO_DGRAM (1<<4)
    unsigned int sockflags;
    int mark;
    const char *bind_dev;

    /* for stream sockets */
    struct stream_buf stream_buf;
    struct buffer stream_buf_data;
    bool stream_reset;

    /* HTTP proxy */
    struct http_proxy_info *http_proxy;

    /* Socks proxy */
    struct socks_proxy_info *socks_proxy;
    struct link_socket_actual socks_relay; /* Socks UDP relay address */

    /* The OpenVPN server we will use the proxy to connect to */
    const char *proxy_dest_host;
    const char *proxy_dest_port;

    /* Pointer to the server-poll to trigger the timeout in function which have
     * their own loop instead of using the main oop */
    struct event_timeout *server_poll_timeout;

#if PASSTOS_CAPABILITY
    /* used to get/set TOS. */
#if defined(TARGET_LINUX)
    uint8_t ptos;
#else /* all the BSDs, Solaris, MacOS use plain "int" -> see "man ip" there */
    int ptos;
#endif
    bool ptos_defined;
#endif

#ifdef ENABLE_DEBUG
    int gremlin; /* --gremlin bits */
#endif
};

/*
 * Some Posix/Win32 differences.
 */

#ifndef MSG_NOSIGNAL
#define MSG_NOSIGNAL 0
#endif

#ifdef _WIN32

#define openvpn_close_socket(s) closesocket(s)

int socket_recv_queue(struct link_socket *sock, int maxsize);

int socket_send_queue(struct link_socket *sock,
                      struct buffer *buf,
                      const struct link_socket_actual *to);

int socket_finalize(
    SOCKET s,
    struct overlapped_io *io,
    struct buffer *buf,
    struct link_socket_actual *from);

#else  /* ifdef _WIN32 */

#define openvpn_close_socket(s) close(s)

#endif

struct link_socket *link_socket_new(void);

void socket_bind(socket_descriptor_t sd,
                 struct addrinfo *local,
                 int af_family,
                 const char *prefix,
                 bool ipv6only);

int openvpn_connect(socket_descriptor_t sd,
                    const struct sockaddr *remote,
                    int connect_timeout,
                    volatile int *signal_received);


/*
 * Initialize link_socket object.
 */
/* *INDENT-OFF* uncrustify misparses this function declarion because of
 * embedded #if/#endif tell it to skip this section */
void
link_socket_init_phase1(struct link_socket *sock,
                        const char *local_host,
                        const char *local_port,
                        const char *remote_host,
                        const char *remote_port,
                        struct cached_dns_entry *dns_cache,
                        int proto,
                        sa_family_t af,
                        bool bind_ipv6_only,
                        int mode,
                        const struct link_socket *accept_from,
                        struct http_proxy_info *http_proxy,
                        struct socks_proxy_info *socks_proxy,
#ifdef ENABLE_DEBUG
                        int gremlin,
#endif
                        bool bind_local,
                        bool remote_float,
                        int inetd,
                        struct link_socket_addr *lsa,
                        const char *ipchange_command,
                        const struct plugin_list *plugins,
                        int resolve_retry_seconds,
                        int mtu_discover_type,
                        int rcvbuf,
                        int sndbuf,
                        int mark,
                        const char *bind_dev,
                        struct event_timeout *server_poll_timeout,
                        unsigned int sockflags);
/* Reenable uncrustify *INDENT-ON* */

void link_socket_init_phase2(struct link_socket *sock,
                             const struct frame *frame,
                             struct signal_info *sig_info);

void do_preresolve(struct context *c);

void socket_adjust_frame_parameters(struct frame *frame, int proto);

void frame_adjust_path_mtu(struct frame *frame, int pmtu, int proto);

void link_socket_close(struct link_socket *sock);

void sd_close(socket_descriptor_t *sd);

#define PS_SHOW_PORT_IF_DEFINED (1<<0)
#define PS_SHOW_PORT            (1<<1)
#define PS_SHOW_PKTINFO         (1<<2)
#define PS_DONT_SHOW_ADDR       (1<<3)
#define PS_DONT_SHOW_FAMILY     (1<<4)

const char *print_sockaddr_ex(const struct sockaddr *addr,
                              const char *separator,
                              const unsigned int flags,
                              struct gc_arena *gc);

static inline
const char *
print_openvpn_sockaddr_ex(const struct openvpn_sockaddr *addr,
                          const char *separator,
                          const unsigned int flags,
                          struct gc_arena *gc)
{
    return print_sockaddr_ex(&addr->addr.sa, separator, flags, gc);
}

static inline
const char *
print_openvpn_sockaddr(const struct openvpn_sockaddr *addr,
                       struct gc_arena *gc)
{
    return print_sockaddr_ex(&addr->addr.sa, ":", PS_SHOW_PORT, gc);
}

static inline
const char *
print_sockaddr(const struct sockaddr *addr,
               struct gc_arena *gc)
{
    return print_sockaddr_ex(addr, ":", PS_SHOW_PORT, gc);
}


const char *print_link_socket_actual_ex(const struct link_socket_actual *act,
                                        const char *separator,
                                        const unsigned int flags,
                                        struct gc_arena *gc);

const char *print_link_socket_actual(const struct link_socket_actual *act,
                                     struct gc_arena *gc);


#define IA_EMPTY_IF_UNDEF (1<<0)
#define IA_NET_ORDER      (1<<1)
const char *print_in_addr_t(in_addr_t addr, unsigned int flags, struct gc_arena *gc);

const char *print_in6_addr(struct in6_addr addr6, unsigned int flags, struct gc_arena *gc);

struct in6_addr add_in6_addr( struct in6_addr base, uint32_t add );

#define SA_IP_PORT        (1<<0)
#define SA_SET_IF_NONZERO (1<<1)
void setenv_sockaddr(struct env_set *es,
                     const char *name_prefix,
                     const struct openvpn_sockaddr *addr,
                     const unsigned int flags);

void setenv_in_addr_t(struct env_set *es,
                      const char *name_prefix,
                      in_addr_t addr,
                      const unsigned int flags);

void setenv_in6_addr(struct env_set *es,
                     const char *name_prefix,
                     const struct in6_addr *addr,
                     const unsigned int flags);

void setenv_link_socket_actual(struct env_set *es,
                               const char *name_prefix,
                               const struct link_socket_actual *act,
                               const unsigned int flags);

void bad_address_length(int actual, int expected);

/* IPV4_INVALID_ADDR: returned by link_socket_current_remote()
 * to ease redirect-gateway logic for ipv4 tunnels on ipv6 endpoints
 */
#define IPV4_INVALID_ADDR 0xffffffff
in_addr_t link_socket_current_remote(const struct link_socket_info *info);

const struct in6_addr *link_socket_current_remote_ipv6
    (const struct link_socket_info *info);

void link_socket_connection_initiated(struct link_socket_info *info,
                                      const struct link_socket_actual *addr,
                                      const char *common_name,
                                      struct env_set *es);

void link_socket_bad_incoming_addr(struct buffer *buf,
                                   const struct link_socket_info *info,
                                   const struct link_socket_actual *from_addr);

void set_actual_address(struct link_socket_actual *actual,
                        struct addrinfo *ai);

void link_socket_bad_outgoing_addr(void);

void setenv_trusted(struct env_set *es, const struct link_socket_info *info);

bool link_socket_update_flags(struct link_socket *ls, unsigned int sockflags);

void link_socket_update_buffer_sizes(struct link_socket *ls, int rcvbuf, int sndbuf);

/*
 * Low-level functions
 */

/* return values of openvpn_inet_aton */
#define OIA_HOSTNAME   0
#define OIA_IP         1
#define OIA_ERROR     -1
int openvpn_inet_aton(const char *dotted_quad, struct in_addr *addr);

/* integrity validation on pulled options */
bool ip_addr_dotted_quad_safe(const char *dotted_quad);

bool ip_or_dns_addr_safe(const char *addr, const bool allow_fqdn);

bool mac_addr_safe(const char *mac_addr);

bool ipv6_addr_safe(const char *ipv6_text_addr);

socket_descriptor_t create_socket_tcp(struct addrinfo *);

socket_descriptor_t socket_do_accept(socket_descriptor_t sd,
                                     struct link_socket_actual *act,
                                     const bool nowait);

/*
 * proto related
 */
bool proto_is_net(int proto);

bool proto_is_dgram(int proto);

bool proto_is_udp(int proto);

bool proto_is_tcp(int proto);


#if UNIX_SOCK_SUPPORT

socket_descriptor_t create_socket_unix(void);

void socket_bind_unix(socket_descriptor_t sd,
                      struct sockaddr_un *local,
                      const char *prefix);

socket_descriptor_t socket_accept_unix(socket_descriptor_t sd,
                                       struct sockaddr_un *remote);

int socket_connect_unix(socket_descriptor_t sd,
                        struct sockaddr_un *remote);

void sockaddr_unix_init(struct sockaddr_un *local, const char *path);

const char *sockaddr_unix_name(const struct sockaddr_un *local, const char *null);

void socket_delete_unix(const struct sockaddr_un *local);

bool unix_socket_get_peer_uid_gid(const socket_descriptor_t sd, int *uid, int *gid);

#endif /* if UNIX_SOCK_SUPPORT */

/*
 * DNS resolution
 */

#define GETADDR_RESOLVE               (1<<0)
#define GETADDR_FATAL                 (1<<1)
#define GETADDR_HOST_ORDER            (1<<2)
#define GETADDR_MENTION_RESOLVE_RETRY (1<<3)
#define GETADDR_FATAL_ON_SIGNAL       (1<<4)
#define GETADDR_WARN_ON_SIGNAL        (1<<5)
#define GETADDR_MSG_VIRT_OUT          (1<<6)
#define GETADDR_TRY_ONCE              (1<<7)
#define GETADDR_UPDATE_MANAGEMENT_STATE (1<<8)
#define GETADDR_RANDOMIZE             (1<<9)
#define GETADDR_PASSIVE               (1<<10)
#define GETADDR_DATAGRAM              (1<<11)

#define GETADDR_CACHE_MASK              (GETADDR_DATAGRAM|GETADDR_PASSIVE)

/**
 * Translate an IPv4 addr or hostname from string form to in_addr_t
 *
 * In case of resolve error, it will try again for
 * resolve_retry_seconds seconds.
 */
in_addr_t getaddr(unsigned int flags,
                  const char *hostname,
                  int resolve_retry_seconds,
                  bool *succeeded,
                  volatile int *signal_received);

/**
 * Translate an IPv6 addr or hostname from string form to in6_addr
 */
bool get_ipv6_addr(const char *hostname, struct in6_addr *network,
                   unsigned int *netbits, int msglevel);

int openvpn_getaddrinfo(unsigned int flags,
                        const char *hostname,
                        const char *servname,
                        int resolve_retry_seconds,
                        volatile int *signal_received,
                        int ai_family,
                        struct addrinfo **res);

/*
 * Transport protocol naming and other details.
 */

/*
 * Use enum's instead of #define to allow for easier
 * optional proto support
 */
enum proto_num {
    PROTO_NONE,     /* catch for uninitialized */
    PROTO_UDP,
    PROTO_TCP,
    PROTO_TCP_SERVER,
    PROTO_TCP_CLIENT,
    PROTO_N
};

int ascii2proto(const char *proto_name);

sa_family_t ascii2af(const char *proto_name);

const char *proto2ascii(int proto, sa_family_t af, bool display_form);

const char *proto2ascii_all(struct gc_arena *gc);

const char *proto_remote(int proto, bool remote);

const char *addr_family_name(int af);

/*
 * Overhead added to packets by various protocols.
 */
#define IPv4_UDP_HEADER_SIZE              28
#define IPv4_TCP_HEADER_SIZE              40
#define IPv6_UDP_HEADER_SIZE              48
#define IPv6_TCP_HEADER_SIZE              60

extern const int proto_overhead[];

static inline int
datagram_overhead(int proto)
{
    ASSERT(proto >= 0 && proto < PROTO_N);
    return proto_overhead [proto];
}

/*
 * Misc inline functions
 */

static inline bool
link_socket_proto_connection_oriented(int proto)
{
    return !proto_is_dgram(proto);
}

static inline bool
link_socket_connection_oriented(const struct link_socket *sock)
{
    if (sock)
    {
        return link_socket_proto_connection_oriented(sock->info.proto);
    }
    else
    {
        return false;
    }
}

static inline bool
addr_defined(const struct openvpn_sockaddr *addr)
{
    if (!addr)
    {
        return 0;
    }
    switch (addr->addr.sa.sa_family)
    {
        case AF_INET: return addr->addr.in4.sin_addr.s_addr != 0;

        case AF_INET6: return !IN6_IS_ADDR_UNSPECIFIED(&addr->addr.in6.sin6_addr);

        default: return 0;
    }
}

static inline bool
addr_local(const struct sockaddr *addr)
{
    if (!addr)
    {
        return false;
    }
    switch (addr->sa_family)
    {
        case AF_INET:
            return ((const struct sockaddr_in *)addr)->sin_addr.s_addr == htonl(INADDR_LOOPBACK);

        case AF_INET6:
            return IN6_IS_ADDR_LOOPBACK(&((const struct sockaddr_in6 *)addr)->sin6_addr);

        default:
            return false;
    }
}


static inline bool
addr_defined_ipi(const struct link_socket_actual *lsa)
{
#if ENABLE_IP_PKTINFO
    if (!lsa)
    {
        return 0;
    }
    switch (lsa->dest.addr.sa.sa_family)
    {
#if defined(HAVE_IN_PKTINFO) && defined(HAVE_IPI_SPEC_DST)
        case AF_INET: return lsa->pi.in4.ipi_spec_dst.s_addr != 0;

#elif defined(IP_RECVDSTADDR)
        case AF_INET: return lsa->pi.in4.s_addr != 0;

#endif
        case AF_INET6: return !IN6_IS_ADDR_UNSPECIFIED(&lsa->pi.in6.ipi6_addr);

        default: return 0;
    }
#else  /* if ENABLE_IP_PKTINFO */
    ASSERT(0);
#endif
    return false;
}

static inline bool
link_socket_actual_defined(const struct link_socket_actual *act)
{
    return act && addr_defined(&act->dest);
}

static inline bool
addr_match(const struct openvpn_sockaddr *a1, const struct openvpn_sockaddr *a2)
{
    switch (a1->addr.sa.sa_family)
    {
        case AF_INET:
            return a1->addr.in4.sin_addr.s_addr == a2->addr.in4.sin_addr.s_addr;

        case AF_INET6:
            return IN6_ARE_ADDR_EQUAL(&a1->addr.in6.sin6_addr, &a2->addr.in6.sin6_addr);
    }
    ASSERT(0);
    return false;
}

static inline bool
addrlist_match(const struct openvpn_sockaddr *a1, const struct addrinfo *addrlist)
{
    const struct addrinfo *curele;
    for (curele = addrlist; curele; curele = curele->ai_next)
    {
        switch (a1->addr.sa.sa_family)
        {
            case AF_INET:
                if (a1->addr.in4.sin_addr.s_addr == ((struct sockaddr_in *)curele->ai_addr)->sin_addr.s_addr)
                {
                    return true;
                }
                break;

            case AF_INET6:
                if (IN6_ARE_ADDR_EQUAL(&a1->addr.in6.sin6_addr, &((struct sockaddr_in6 *) curele->ai_addr)->sin6_addr))
                {
                    return true;
                }
                break;

            default:
                ASSERT(0);
        }
    }
    return false;
}

static inline in_addr_t
addr_host(const struct openvpn_sockaddr *addr)
{
    /*
     * "public" addr returned is checked against ifconfig for
     * possible clash: non sense for now given
     * that we do ifconfig only IPv4
     */
    if (addr->addr.sa.sa_family != AF_INET)
    {
        return 0;
    }
    return ntohl(addr->addr.in4.sin_addr.s_addr);
}


static inline bool
addrlist_port_match(const struct openvpn_sockaddr *a1, const struct addrinfo *a2)
{
    const struct addrinfo *curele;
    for (curele = a2; curele; curele = curele->ai_next)
    {
        switch (a1->addr.sa.sa_family)
        {
            case AF_INET:
                if (curele->ai_family == AF_INET
                    && a1->addr.in4.sin_addr.s_addr == ((struct sockaddr_in *)curele->ai_addr)->sin_addr.s_addr
                    && a1->addr.in4.sin_port == ((struct sockaddr_in *)curele->ai_addr)->sin_port)
                {
                    return true;
                }
                break;

            case AF_INET6:
                if (curele->ai_family == AF_INET6
                    && IN6_ARE_ADDR_EQUAL(&a1->addr.in6.sin6_addr, &((struct sockaddr_in6 *) curele->ai_addr)->sin6_addr)
                    && a1->addr.in6.sin6_port == ((struct sockaddr_in6 *) curele->ai_addr)->sin6_port)
                {
                    return true;
                }
                break;

            default:
                ASSERT(0);
        }
    }
    return false;
}


static inline bool
addr_port_match(const struct openvpn_sockaddr *a1, const struct openvpn_sockaddr *a2)
{
    switch (a1->addr.sa.sa_family)
    {
        case AF_INET:
            return a1->addr.in4.sin_addr.s_addr == a2->addr.in4.sin_addr.s_addr
                   && a1->addr.in4.sin_port == a2->addr.in4.sin_port;

        case AF_INET6:
            return IN6_ARE_ADDR_EQUAL(&a1->addr.in6.sin6_addr, &a2->addr.in6.sin6_addr)
                   && a1->addr.in6.sin6_port == a2->addr.in6.sin6_port;
    }
    ASSERT(0);
    return false;
}

static inline bool
addr_match_proto(const struct openvpn_sockaddr *a1,
                 const struct openvpn_sockaddr *a2,
                 const int proto)
{
    return link_socket_proto_connection_oriented(proto)
           ? addr_match(a1, a2)
           : addr_port_match(a1, a2);
}


static inline bool
addrlist_match_proto(const struct openvpn_sockaddr *a1,
                     struct addrinfo *addr_list,
                     const int proto)
{
    return link_socket_proto_connection_oriented(proto)
           ? addrlist_match(a1, addr_list)
           : addrlist_port_match(a1, addr_list);
}

static inline void
addr_zero_host(struct openvpn_sockaddr *addr)
{
    switch (addr->addr.sa.sa_family)
    {
        case AF_INET:
            addr->addr.in4.sin_addr.s_addr = 0;
            break;

        case AF_INET6:
            memset(&addr->addr.in6.sin6_addr, 0, sizeof(struct in6_addr));
            break;
    }
}

static inline void
addr_copy_sa(struct openvpn_sockaddr *dst, const struct openvpn_sockaddr *src)
{
    dst->addr = src->addr;
}

static inline bool
addr_inet4or6(struct sockaddr *addr)
{
    return addr->sa_family == AF_INET || addr->sa_family == AF_INET6;
}

int addr_guess_family(sa_family_t af,const char *name);

static inline int
af_addr_size(sa_family_t af)
{
    switch (af)
    {
        case AF_INET: return sizeof(struct sockaddr_in);

        case AF_INET6: return sizeof(struct sockaddr_in6);

        default:
#if 0
            /* could be called from socket_do_accept() with empty addr */
            msg(M_ERR, "Bad address family: %d\n", af);
            ASSERT(0);
#endif
            return 0;
    }
}

static inline bool
link_socket_actual_match(const struct link_socket_actual *a1, const struct link_socket_actual *a2)
{
    return addr_port_match(&a1->dest, &a2->dest);
}

#if PORT_SHARE

static inline bool
socket_foreign_protocol_detected(const struct link_socket *sock)
{
    return link_socket_connection_oriented(sock)
           && sock->stream_buf.port_share_state == PS_FOREIGN;
}

static inline const struct buffer *
socket_foreign_protocol_head(const struct link_socket *sock)
{
    return &sock->stream_buf.buf;
}

static inline int
socket_foreign_protocol_sd(const struct link_socket *sock)
{
    return sock->sd;
}

#endif /* if PORT_SHARE */

static inline bool
socket_connection_reset(const struct link_socket *sock, int status)
{
    if (link_socket_connection_oriented(sock))
    {
        if (sock->stream_reset || sock->stream_buf.error)
        {
            return true;
        }
        else if (status < 0)
        {
            const int err = openvpn_errno();
#ifdef _WIN32
            return err == WSAECONNRESET || err == WSAECONNABORTED;
#else
            return err == ECONNRESET;
#endif
        }
    }
    return false;
}

static inline bool
link_socket_verify_incoming_addr(struct buffer *buf,
                                 const struct link_socket_info *info,
                                 const struct link_socket_actual *from_addr)
{
    if (buf->len > 0)
    {
        switch (from_addr->dest.addr.sa.sa_family)
        {
            case AF_INET6:
            case AF_INET:
                if (!link_socket_actual_defined(from_addr))
                {
                    return false;
                }
                if (info->remote_float || (!info->lsa->remote_list))
                {
                    return true;
                }
                if (addrlist_match_proto(&from_addr->dest, info->lsa->remote_list, info->proto))
                {
                    return true;
                }
        }
    }
    return false;
}

static inline void
link_socket_get_outgoing_addr(struct buffer *buf,
                              const struct link_socket_info *info,
                              struct link_socket_actual **act)
{
    if (buf->len > 0)
    {
        struct link_socket_addr *lsa = info->lsa;
        if (link_socket_actual_defined(&lsa->actual))
        {
            *act = &lsa->actual;
        }
        else
        {
            link_socket_bad_outgoing_addr();
            buf->len = 0;
            *act = NULL;
        }
    }
}

static inline void
link_socket_set_outgoing_addr(struct link_socket_info *info,
                              const struct link_socket_actual *act,
                              const char *common_name,
                              struct env_set *es)
{
    struct link_socket_addr *lsa = info->lsa;
    if (
        /* new or changed address? */
        (!info->connection_established
         || !addr_match_proto(&act->dest, &lsa->actual.dest, info->proto)
        )
        &&
        /* address undef or address == remote or --float */
        (info->remote_float
         || (!lsa->remote_list || addrlist_match_proto(&act->dest, lsa->remote_list, info->proto))
        )
        )
    {
        link_socket_connection_initiated(info, act, common_name, es);
    }
}

bool stream_buf_read_setup_dowork(struct link_socket *sock);

static inline bool
stream_buf_read_setup(struct link_socket *sock)
{
    if (link_socket_connection_oriented(sock))
    {
        return stream_buf_read_setup_dowork(sock);
    }
    else
    {
        return true;
    }
}

/*
 * Socket Read Routines
 */

int link_socket_read_tcp(struct link_socket *sock,
                         struct buffer *buf);

#ifdef _WIN32

static inline int
link_socket_read_udp_win32(struct link_socket *sock,
                           struct buffer *buf,
                           struct link_socket_actual *from)
{
    return socket_finalize(sock->sd, &sock->reads, buf, from);
}

#else  /* ifdef _WIN32 */

int link_socket_read_udp_posix(struct link_socket *sock,
                               struct buffer *buf,
                               struct link_socket_actual *from);

#endif

/* read a TCP or UDP packet from link */
static inline int
link_socket_read(struct link_socket *sock,
                 struct buffer *buf,
                 struct link_socket_actual *from)
{
    if (proto_is_udp(sock->info.proto)) /* unified UDPv4 and UDPv6 */
    {
        int res;

#ifdef _WIN32
        res = link_socket_read_udp_win32(sock, buf, from);
#else
        res = link_socket_read_udp_posix(sock, buf, from);
#endif
        return res;
    }
    else if (proto_is_tcp(sock->info.proto)) /* unified TCPv4 and TCPv6 */
    {
        /* from address was returned by accept */
        addr_copy_sa(&from->dest, &sock->info.lsa->actual.dest);
        return link_socket_read_tcp(sock, buf);
    }
    else
    {
        ASSERT(0);
        return -1; /* NOTREACHED */
    }
}

/*
 * Socket Write routines
 */

int link_socket_write_tcp(struct link_socket *sock,
                          struct buffer *buf,
                          struct link_socket_actual *to);

#ifdef _WIN32

static inline int
link_socket_write_win32(struct link_socket *sock,
                        struct buffer *buf,
                        struct link_socket_actual *to)
{
    int err = 0;
    int status = 0;
    if (overlapped_io_active(&sock->writes))
    {
        status = socket_finalize(sock->sd, &sock->writes, NULL, NULL);
        if (status < 0)
        {
            err = WSAGetLastError();
        }
    }
    socket_send_queue(sock, buf, to);
    if (status < 0)
    {
        WSASetLastError(err);
        return status;
    }
    else
    {
        return BLEN(buf);
    }
}

#else  /* ifdef _WIN32 */

size_t link_socket_write_udp_posix_sendmsg(struct link_socket *sock,
                                           struct buffer *buf,
                                           struct link_socket_actual *to);


static inline size_t
link_socket_write_udp_posix(struct link_socket *sock,
                            struct buffer *buf,
                            struct link_socket_actual *to)
{
#if ENABLE_IP_PKTINFO
    if (proto_is_udp(sock->info.proto) && (sock->sockflags & SF_USE_IP_PKTINFO)
        && addr_defined_ipi(to))
    {
        return link_socket_write_udp_posix_sendmsg(sock, buf, to);
    }
    else
#endif
    return sendto(sock->sd, BPTR(buf), BLEN(buf), 0,
                  (struct sockaddr *) &to->dest.addr.sa,
                  (socklen_t) af_addr_size(to->dest.addr.sa.sa_family));
}

static inline size_t
link_socket_write_tcp_posix(struct link_socket *sock,
                            struct buffer *buf,
                            struct link_socket_actual *to)
{
    return send(sock->sd, BPTR(buf), BLEN(buf), MSG_NOSIGNAL);
}

#endif /* ifdef _WIN32 */

static inline size_t
link_socket_write_udp(struct link_socket *sock,
                      struct buffer *buf,
                      struct link_socket_actual *to)
{
#ifdef _WIN32
    return link_socket_write_win32(sock, buf, to);
#else
    return link_socket_write_udp_posix(sock, buf, to);
#endif
}

/* write a TCP or UDP packet to link */
static inline int
link_socket_write(struct link_socket *sock,
                  struct buffer *buf,
                  struct link_socket_actual *to)
{
    if (proto_is_udp(sock->info.proto)) /* unified UDPv4 and UDPv6 */
    {
        return link_socket_write_udp(sock, buf, to);
    }
    else if (proto_is_tcp(sock->info.proto)) /* unified TCPv4 and TCPv6 */
    {
        return link_socket_write_tcp(sock, buf, to);
    }
    else
    {
        ASSERT(0);
        return -1; /* NOTREACHED */
    }
}

#if PASSTOS_CAPABILITY

/*
 * Extract TOS bits.  Assumes that ipbuf is a valid IPv4 packet.
 */
static inline void
link_socket_extract_tos(struct link_socket *ls, const struct buffer *ipbuf)
{
    if (ls && ipbuf)
    {
        struct openvpn_iphdr *iph = (struct openvpn_iphdr *) BPTR(ipbuf);
        ls->ptos = iph->tos;
        ls->ptos_defined = true;
    }
}

/*
 * Set socket properties to reflect TOS bits which were extracted
 * from tunnel packet.
 */
static inline void
link_socket_set_tos(struct link_socket *ls)
{
    if (ls && ls->ptos_defined)
    {
        setsockopt(ls->sd, IPPROTO_IP, IP_TOS, (const void *)&ls->ptos, sizeof(ls->ptos));
    }
}

#endif /* if PASSTOS_CAPABILITY */

/*
 * Socket I/O wait functions
 */

static inline bool
socket_read_residual(const struct link_socket *s)
{
    return s && s->stream_buf.residual_fully_formed;
}

static inline event_t
socket_event_handle(const struct link_socket *s)
{
#ifdef _WIN32
    return &s->rw_handle;
#else
    return s->sd;
#endif
}

event_t socket_listen_event_handle(struct link_socket *s);

unsigned int
socket_set(struct link_socket *s,
           struct event_set *es,
           unsigned int rwflags,
           void *arg,
           unsigned int *persistent);

static inline void
socket_set_listen_persistent(struct link_socket *s,
                             struct event_set *es,
                             void *arg)
{
    if (s && !s->listen_persistent_queued)
    {
        event_ctl(es, socket_listen_event_handle(s), EVENT_READ, arg);
        s->listen_persistent_queued = true;
    }
}

static inline void
socket_reset_listen_persistent(struct link_socket *s)
{
#ifdef _WIN32
    reset_net_event_win32(&s->listen_handle, s->sd);
#endif
}

const char *socket_stat(const struct link_socket *s, unsigned int rwflags, struct gc_arena *gc);

#endif /* SOCKET_H */