#include <net-snmp/net-snmp-config.h>

#include <stdio.h>
#include <sys/types.h>
#include <errno.h>

#if HAVE_STRING_H
#include <string.h>
#else
#include <strings.h>
#endif
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#if HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#if HAVE_FCNTL_H
#include <fcntl.h>
#endif

#if HAVE_WINSOCK_H
#include <winsock2.h>
#include <ws2tcpip.h>
#endif

#if HAVE_DMALLOC_H
#include <dmalloc.h>
#endif

#include <net-snmp/types.h>
#include <net-snmp/output_api.h>

#include <net-snmp/library/snmp_transport.h>
#include <net-snmp/library/snmpUDPDomain.h>
#include <net-snmp/library/snmpTCPDomain.h>

/* Copied from snmpUDPDomain.c */
typedef struct netsnmp_udp_addr_pair_s {
    struct sockaddr_in remote_addr;
    struct in_addr local_addr;
} netsnmp_udp_addr_pair;

oid netsnmp_snmpTCPDomain[] = { TRANSPORT_DOMAIN_TCP_IP };
static netsnmp_tdomain tcpDomain;

/*
 * Not static since it is needed here as well as in snmpUDPDomain, but not
 * public either
 */
int
netsnmp_sockaddr_in2(struct sockaddr_in *addr,
                     const char *inpeername, const char *default_target);

/*
 * Return a string representing the address in data, or else the "far end"
 * address if data is NULL.  
 */

static char *
netsnmp_tcp_fmtaddr(netsnmp_transport *t, void *data, int len)
{
    netsnmp_udp_addr_pair *addr_pair = NULL;

    if (data != NULL && len == sizeof(netsnmp_udp_addr_pair)) {
	addr_pair = (netsnmp_udp_addr_pair *) data;
    } else if (t != NULL && t->data != NULL) {
	addr_pair = (netsnmp_udp_addr_pair *) t->data;
    }

    if (addr_pair == NULL) {
        return strdup("TCP: unknown");
    } else {
        struct sockaddr_in *to = NULL;
	char tmp[64];
        to = (struct sockaddr_in *) &(addr_pair->remote_addr);
        if (to == NULL) {
            return strdup("TCP: unknown");
        }

        sprintf(tmp, "TCP: [%s]:%hu",
                inet_ntoa(to->sin_addr), ntohs(to->sin_port));
        return strdup(tmp);
    }
}


/*
 * You can write something into opaque that will subsequently get passed back 
 * to your send function if you like.  For instance, you might want to
 * remember where a PDU came from, so that you can send a reply there...  
 */

static int
netsnmp_tcp_recv(netsnmp_transport *t, void *buf, int size,
		 void **opaque, int *olength)
{
    int rc = -1;

    if (t != NULL && t->sock >= 0) {
	while (rc < 0) {
	    rc = recvfrom(t->sock, buf, size, 0, NULL, NULL);
	    if (rc < 0 && errno != EINTR) {
		DEBUGMSGTL(("netsnmp_tcp", "recv fd %d err %d (\"%s\")\n",
			    t->sock, errno, strerror(errno)));
		break;
	    }
	    DEBUGMSGTL(("netsnmp_tcp", "recv fd %d got %d bytes\n",
			t->sock, rc));
	}
    } else {
        return -1;
    }

    if (opaque != NULL && olength != NULL) {
        if (t->data_length > 0) {
            if ((*opaque = malloc(t->data_length)) != NULL) {
                memcpy(*opaque, t->data, t->data_length);
                *olength = t->data_length;
            } else {
                *olength = 0;
            }
        } else {
            *opaque = NULL;
            *olength = 0;
        }
    }

    return rc;
}


static int
netsnmp_tcp_send(netsnmp_transport *t, void *buf, int size,
		 void **opaque, int *olength)
{
    int rc = -1;

    if (t != NULL && t->sock >= 0) {
	while (rc < 0) {
	    rc = sendto(t->sock, buf, size, 0, NULL, 0);
	    if (rc < 0 && errno != EINTR) {
		break;
	    }
	}
    }
    return rc;
}


static int
netsnmp_tcp_close(netsnmp_transport *t)
{
    int rc = -1;
    if (t != NULL && t->sock >= 0) {
        DEBUGMSGTL(("netsnmp_tcp", "close fd %d\n", t->sock));
#ifndef HAVE_CLOSESOCKET
        rc = close(t->sock);
#else
        rc = closesocket(t->sock);
#endif
        t->sock = -1;
    }
    return rc;
}


static int
netsnmp_tcp_accept(netsnmp_transport *t)
{
    struct sockaddr *farend = NULL;
    netsnmp_udp_addr_pair *addr_pair = NULL;
    int             newsock = -1;
#ifdef WIN32
    u_long          ioctlsocket_opt;
#else
    int             sockflags;
#endif
    socklen_t       farendlen = sizeof(struct sockaddr_in);
    char           *str = NULL;

    addr_pair = (netsnmp_udp_addr_pair *)malloc(sizeof(netsnmp_udp_addr_pair));

    if (addr_pair == NULL) {
        /*
         * Indicate that the acceptance of this socket failed.  
         */
        DEBUGMSGTL(("netsnmp_tcp", "accept: malloc failed\n"));
        return -1;
    }
    farend = (struct sockaddr *) &(addr_pair->remote_addr);

    if (t != NULL && t->sock >= 0) {
        newsock = accept(t->sock, farend, &farendlen);

        if (newsock < 0) {
            DEBUGMSGTL(("netsnmp_tcp", "accept failed rc %d errno %d \"%s\"\n",
			newsock, errno, strerror(errno)));
            free(farend);
            return newsock;
        }

        if (t->data != NULL) {
            free(t->data);
        }

        t->data = addr_pair;
        t->data_length = sizeof(netsnmp_udp_addr_pair);
        str = netsnmp_tcp_fmtaddr(NULL, farend, farendlen);
        DEBUGMSGTL(("netsnmp_tcp", "accept succeeded (from %s)\n", str));
        free(str);

        /*
         * Try to make the new socket blocking.  
         */

#ifdef WIN32
        ioctlsocket_opt = 0;
        ioctlsocket(newsock, FIONBIO, &ioctlsocket_opt);
#else
        if ((sockflags = fcntl(newsock, F_GETFL, 0)) >= 0) {
            fcntl(newsock, F_SETFL, (sockflags & ~O_NONBLOCK));
        } else {
            DEBUGMSGTL(("netsnmp_tcp", "couldn't f_getfl of fd %d\n",newsock));
        }
#endif

        /*
         * Allow user to override the send and receive buffers. Default is
         * to use os default.  Don't worry too much about errors --
         * just plough on regardless.  
         */
        netsnmp_sock_buffer_set(newsock, SO_SNDBUF, 1, 0);
        netsnmp_sock_buffer_set(newsock, SO_RCVBUF, 1, 0);

        return newsock;
    } else {
        free(farend);
        return -1;
    }
}


/*
 * Open a TCP-based transport for SNMP.  Local is TRUE if addr is the local
 * address to bind to (i.e. this is a server-type session); otherwise addr is 
 * the remote address to send things to.  
 */

netsnmp_transport *
netsnmp_tcp_transport(struct sockaddr_in *addr, int local)
{
    netsnmp_transport *t = NULL;
    netsnmp_udp_addr_pair *addr_pair = NULL;
    int rc = 0;


    if (addr == NULL || addr->sin_family != AF_INET) {
        return NULL;
    }

    t = (netsnmp_transport *) malloc(sizeof(netsnmp_transport));
    if (t == NULL) {
        return NULL;
    }
    memset(t, 0, sizeof(netsnmp_transport));

    addr_pair = (netsnmp_udp_addr_pair *)malloc(sizeof(netsnmp_udp_addr_pair));
    if (addr_pair == NULL) {
        netsnmp_transport_free(t);
        return NULL;
    }
    t->data = addr_pair;
    t->data_length = sizeof(netsnmp_udp_addr_pair);
    memcpy(&(addr_pair->remote_addr), addr, sizeof(struct sockaddr_in));

    t->domain = netsnmp_snmpTCPDomain;
    t->domain_length =
        sizeof(netsnmp_snmpTCPDomain) / sizeof(netsnmp_snmpTCPDomain[0]);

    t->sock = socket(PF_INET, SOCK_STREAM, 0);
    if (t->sock < 0) {
        netsnmp_transport_free(t);
        return NULL;
    }

    t->flags = NETSNMP_TRANSPORT_FLAG_STREAM;

    if (local) {
#ifdef WIN32
        u_long ioctlsocket_opt = 1;
#else
        int sockflags = 0;
#endif
        int opt = 1;

        /*
         * This session is inteneded as a server, so we must bind to the given 
         * IP address (which may include an interface address, or could be
         * INADDR_ANY, but will always include a port number.  
         */

        t->flags |= NETSNMP_TRANSPORT_FLAG_LISTEN;
        t->local = (u_char *)malloc(6);
        if (t->local == NULL) {
            netsnmp_tcp_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }
        memcpy(t->local, (u_char *) & (addr->sin_addr.s_addr), 4);
        t->local[4] = (htons(addr->sin_port) & 0xff00) >> 8;
        t->local[5] = (htons(addr->sin_port) & 0x00ff) >> 0;
        t->local_length = 6;

        /*
         * We should set SO_REUSEADDR too.  
         */

        setsockopt(t->sock, SOL_SOCKET, SO_REUSEADDR, (void *)&opt,
		   sizeof(opt));

        rc = bind(t->sock, (struct sockaddr *)addr, sizeof(struct sockaddr));
        if (rc != 0) {
            netsnmp_tcp_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }

        /*
         * Since we are going to be letting select() tell us when connections
         * are ready to be accept()ed, we need to make the socket n0n-blocking
         * to avoid the race condition described in W. R. Stevens, ``Unix
         * Network Programming Volume I Second Edition'', pp. 422--4, which
         * could otherwise wedge the agent.
         */

#ifdef WIN32
        ioctlsocket_opt = 1;
        ioctlsocket(t->sock, FIONBIO, &ioctlsocket_opt);
#else
        sockflags = fcntl(t->sock, F_GETFL, 0);
        fcntl(t->sock, F_SETFL, sockflags | O_NONBLOCK);
#endif

        /*
         * Now sit here and wait for connections to arrive.  
         */

        rc = listen(t->sock, NETSNMP_STREAM_QUEUE_LEN);
        if (rc != 0) {
            netsnmp_tcp_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }
        
        /*
         * no buffer size on listen socket - doesn't make sense
         */

    } else {
      t->remote = (u_char *)malloc(6);
        if (t->remote == NULL) {
            netsnmp_tcp_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }
        memcpy(t->remote, (u_char *) & (addr->sin_addr.s_addr), 4);
        t->remote[4] = (htons(addr->sin_port) & 0xff00) >> 8;
        t->remote[5] = (htons(addr->sin_port) & 0x00ff) >> 0;
        t->remote_length = 6;

        /*
         * This is a client-type session, so attempt to connect to the far
         * end.  We don't go non-blocking here because it's not obvious what
         * you'd then do if you tried to do snmp_sends before the connection
         * had completed.  So this can block.
         */

        rc = connect(t->sock, (struct sockaddr *)addr,
		     sizeof(struct sockaddr));

        if (rc < 0) {
            netsnmp_tcp_close(t);
            netsnmp_transport_free(t);
            return NULL;
        }

        /*
         * Allow user to override the send and receive buffers. Default is
         * to use os default.  Don't worry too much about errors --
         * just plough on regardless.  
         */
        netsnmp_sock_buffer_set(t->sock, SO_SNDBUF, local, 0);
        netsnmp_sock_buffer_set(t->sock, SO_RCVBUF, local, 0);
    }

    /*
     * Message size is not limited by this transport (hence msgMaxSize
     * is equal to the maximum legal size of an SNMP message).  
     */

    t->msgMaxSize = 0x7fffffff;
    t->f_recv     = netsnmp_tcp_recv;
    t->f_send     = netsnmp_tcp_send;
    t->f_close    = netsnmp_tcp_close;
    t->f_accept   = netsnmp_tcp_accept;
    t->f_fmtaddr  = netsnmp_tcp_fmtaddr;

    return t;
}


netsnmp_transport *
netsnmp_tcp_create_tstring(const char *str, int local,
			   const char *default_target)
{
    struct sockaddr_in addr;

    if (netsnmp_sockaddr_in2(&addr, str, default_target)) {
        return netsnmp_tcp_transport(&addr, local);
    } else {
        return NULL;
    }
}


netsnmp_transport *
netsnmp_tcp_create_ostring(const u_char * o, size_t o_len, int local)
{
    struct sockaddr_in addr;

    if (o_len == 6) {
        unsigned short porttmp = (o[4] << 8) + o[5];
        addr.sin_family = AF_INET;
        memcpy((u_char *) & (addr.sin_addr.s_addr), o, 4);
        addr.sin_port = htons(porttmp);
        return netsnmp_tcp_transport(&addr, local);
    }
    return NULL;
}


void
netsnmp_tcp_ctor(void)
{
    tcpDomain.name = netsnmp_snmpTCPDomain;
    tcpDomain.name_length = sizeof(netsnmp_snmpTCPDomain) / sizeof(oid);
    tcpDomain.prefix = (const char **)calloc(2, sizeof(char *));
    tcpDomain.prefix[0] = "tcp";

    tcpDomain.f_create_from_tstring     = NULL;
    tcpDomain.f_create_from_tstring_new = netsnmp_tcp_create_tstring;
    tcpDomain.f_create_from_ostring     = netsnmp_tcp_create_ostring;

    netsnmp_tdomain_register(&tcpDomain);
}