/*
 * $Id: dns_internal.c,v 1.34.2.2 2001/01/12 00:51:47 wessels Exp $
 *
 * DEBUG: section 78    DNS lookups; interacts with lib/rfc1035.c
 * AUTHOR: Duane Wessels
 *
 * SQUID Web Proxy Cache          http://www.squid-cache.org/
 * ----------------------------------------------------------
 *
 *  Squid is the result of efforts by numerous individuals from
 *  the Internet community; see the CONTRIBUTORS file for full
 *  details.   Many organizations have provided support for Squid's
 *  development; see the SPONSORS file for full details.  Squid is
 *  Copyrighted (C) 2001 by the Regents of the University of
 *  California; see the COPYRIGHT file for full details.  Squid
 *  incorporates software developed and/or copyrighted by other
 *  sources; see the CREDITS file for full details.
 *
 *  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.
 *  
 *  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., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
 *
 */

#include "squid.h"

#ifndef _PATH_RESOLV_CONF
#define _PATH_RESOLV_CONF "/etc/resolv.conf"
#endif
#ifndef DOMAIN_PORT
#define DOMAIN_PORT 53
#endif

#define IDNS_MAX_TRIES 20
#define MAX_RCODE 6
#define MAX_ATTEMPT 3
static int RcodeMatrix[MAX_RCODE][MAX_ATTEMPT];

typedef struct _idns_query idns_query;
typedef struct _ns ns;

struct _idns_query {
    char buf[512];
    size_t sz;
    unsigned short id;
    int nsends;
    struct timeval start_t;
    struct timeval sent_t;
    dlink_node lru;
    IDNSCB *callback;
    void *callback_data;
    int attempt;
};

struct _ns {
    struct sockaddr_in S;
    int nqueries;
    int nreplies;
    int large_pkts;
};

static ns *nameservers = NULL;
static int nns = 0;
static int nns_alloc = 0;
static dlink_list lru_list;
static int event_queued = 0;

static OBJH idnsStats;
static void idnsAddNameserver(const char *buf);
static void idnsFreeNameservers(void);
static void idnsParseNameservers(void);
static void idnsParseResolvConf(void);
static void idnsSendQuery(idns_query * q);
static int idnsFromKnownNameserver(struct sockaddr_in *from);
static idns_query *idnsFindQuery(unsigned short id);
static void idnsGrokReply(const char *buf, size_t sz);
static PF idnsRead;
static EVH idnsCheckQueue;
static void idnsTickleQueue(void);
static void idnsRcodeCount(int, int);

static void
idnsAddNameserver(const char *buf)
{
    struct in_addr A;
    if (!safe_inet_addr(buf, &A)) {
	debug(78, 0) ("WARNING: rejecting '%s' as a name server, because it is not a numeric IP address\n", buf);
	return;
    }
    if (nns == nns_alloc) {
	int oldalloc = nns_alloc;
	ns *oldptr = nameservers;
	if (nns_alloc == 0)
	    nns_alloc = 2;
	else
	    nns_alloc <<= 1;
	nameservers = xcalloc(nns_alloc, sizeof(*nameservers));
	if (oldptr && oldalloc)
	    xmemcpy(nameservers, oldptr, oldalloc * sizeof(*nameservers));
	if (oldptr)
	    safe_free(oldptr);
    }
    assert(nns < nns_alloc);
    nameservers[nns].S.sin_family = AF_INET;
    nameservers[nns].S.sin_port = htons(DOMAIN_PORT);
    nameservers[nns].S.sin_addr.s_addr = A.s_addr;
    debug(78, 3) ("idnsAddNameserver: Added nameserver #%d: %s\n",
	nns, inet_ntoa(nameservers[nns].S.sin_addr));
    nns++;
}

static void
idnsFreeNameservers(void)
{
    safe_free(nameservers);
    nns = nns_alloc = 0;
}

static void
idnsParseNameservers(void)
{
    wordlist *w;
    for (w = Config.dns_nameservers; w; w = w->next) {
	debug(78, 1) ("Adding nameserver %s from squid.conf\n", w->key);
	idnsAddNameserver(w->key);
    }
}

static void
idnsParseResolvConf(void)
{
    FILE *fp;
    char buf[512];
    char *t;
    fp = fopen(_PATH_RESOLV_CONF, "r");
    if (fp == NULL) {
	debug(78, 1) ("%s: %s\n", _PATH_RESOLV_CONF, xstrerror());
	return;
    }
#if defined(_SQUID_CYGWIN_)
    setmode(fileno(fp), O_TEXT);
#endif
    while (fgets(buf, 512, fp)) {
	t = strtok(buf, w_space);
	if (NULL == t)
	    continue;
	if (strcasecmp(t, "nameserver"))
	    continue;
	t = strtok(NULL, w_space);
	if (t == NULL)
	    continue;
	debug(78, 1) ("Adding nameserver %s from %s\n", t, _PATH_RESOLV_CONF);
	idnsAddNameserver(t);
    }
    fclose(fp);
}

static void
idnsStats(StoreEntry * sentry)
{
    dlink_node *n;
    idns_query *q;
    int i;
    int j;
    storeAppendPrintf(sentry, "Internal DNS Statistics:\n");
    storeAppendPrintf(sentry, "\nThe Queue:\n");
    storeAppendPrintf(sentry, "                       DELAY SINCE\n");
    storeAppendPrintf(sentry, "  ID   SIZE SENDS FIRST SEND LAST SEND\n");
    storeAppendPrintf(sentry, "------ ---- ----- ---------- ---------\n");
    for (n = lru_list.head; n; n = n->next) {
	q = n->data;
	storeAppendPrintf(sentry, "%#06x %4d %5d %10.3f %9.3f\n",
	    (int) q->id, q->sz, q->nsends,
	    tvSubDsec(q->start_t, current_time),
	    tvSubDsec(q->sent_t, current_time));
    }
    storeAppendPrintf(sentry, "\nNameservers:\n");
    storeAppendPrintf(sentry, "IP ADDRESS      # QUERIES # REPLIES\n");
    storeAppendPrintf(sentry, "--------------- --------- ---------\n");
    for (i = 0; i < nns; i++) {
	storeAppendPrintf(sentry, "%-15s %9d %9d\n",
	    inet_ntoa(nameservers[i].S.sin_addr),
	    nameservers[i].nqueries,
	    nameservers[i].nreplies);
    }
    storeAppendPrintf(sentry, "\nRcode Matrix:\n");
    storeAppendPrintf(sentry, "RCODE");
    for (i = 0; i < MAX_ATTEMPT; i++)
	storeAppendPrintf(sentry, " ATTEMPT%d", i + 1);
    storeAppendPrintf(sentry, "\n");
    for (j = 0; j < MAX_RCODE; j++) {
	storeAppendPrintf(sentry, "%5d", j);
	for (i = 0; i < MAX_ATTEMPT; i++)
	    storeAppendPrintf(sentry, " %8d", RcodeMatrix[j][i]);
	storeAppendPrintf(sentry, "\n");
    }
}

static void
idnsTickleQueue(void)
{
    if (event_queued)
	return;
    if (NULL == lru_list.tail)
	return;
    eventAdd("idnsCheckQueue", idnsCheckQueue, NULL, 1.0, 1);
    event_queued = 1;
}

static void
idnsSendQuery(idns_query * q)
{
    int x;
    int ns;
    if (DnsSocket < 0) {
	debug(78, 1) ("idnsSendQuery: Can't send query, no DNS socket!\n");
	return;
    }
    /* XXX Select nameserver */
    assert(nns > 0);
    assert(q->lru.next == NULL);
    assert(q->lru.prev == NULL);
  try_again:
    ns = q->nsends % nns;
    x = comm_udp_sendto(DnsSocket,
	&nameservers[ns].S,
	sizeof(nameservers[ns].S),
	q->buf,
	q->sz);
    q->nsends++;
    q->sent_t = current_time;
    if (x < 0) {
	debug(50, 1) ("idnsSendQuery: FD %d: sendto: %s\n",
	    DnsSocket, xstrerror());
	if (q->nsends % nns != 0)
	    goto try_again;
    } else {
	fd_bytes(DnsSocket, x, FD_WRITE);
	commSetSelect(DnsSocket, COMM_SELECT_READ, idnsRead, NULL, 0);
    }
    nameservers[ns].nqueries++;
    dlinkAdd(q, &q->lru, &lru_list);
    idnsTickleQueue();
}

static int
idnsFromKnownNameserver(struct sockaddr_in *from)
{
    int i;
    for (i = 0; i < nns; i++) {
	if (nameservers[i].S.sin_addr.s_addr != from->sin_addr.s_addr)
	    continue;
	if (nameservers[i].S.sin_port != from->sin_port)
	    continue;
	return i;
    }
    return -1;
}

static idns_query *
idnsFindQuery(unsigned short id)
{
    dlink_node *n;
    idns_query *q;
    for (n = lru_list.tail; n; n = n->prev) {
	q = n->data;
	if (q->id == id)
	    return q;
    }
    return NULL;
}

static void
idnsGrokReply(const char *buf, size_t sz)
{
    int n;
    int valid;
    rfc1035_rr *answers = NULL;
    unsigned short rid = 0xFFFF;
    idns_query *q;
    n = rfc1035AnswersUnpack(buf,
	sz,
	&answers,
	&rid);
    debug(78, 3) ("idnsGrokReply: ID %#hx, %d answers\n", rid, n);
    if (rid == 0xFFFF) {
	debug(78, 1) ("idnsGrokReply: Unknown error\n");
	/* XXX leak answers? */
	return;
    }
    q = idnsFindQuery(rid);
    if (q == NULL) {
	debug(78, 3) ("idnsGrokReply: Late response\n");
	rfc1035RRDestroy(answers, n);
	return;
    }
    dlinkDelete(&q->lru, &lru_list);
    idnsRcodeCount(n, q->attempt);
    if (n < 0) {
	debug(78, 3) ("idnsGrokReply: error %d\n", rfc1035_errno);
	if (-2 == n && ++q->attempt < MAX_ATTEMPT) {
	    /*
	     * RCODE 2 is "Server failure - The name server was
	     * unable to process this query due to a problem with
	     * the name server."
	     */
	    assert(NULL == answers);
	    q->start_t = current_time;
	    q->id = rfc1035RetryQuery(q->buf);
	    idnsSendQuery(q);
	    return;
	}
    }
    valid = cbdataValid(q->callback_data);
    cbdataUnlock(q->callback_data);
    if (valid)
	q->callback(q->callback_data, answers, n);
    rfc1035RRDestroy(answers, n);
    memFree(q, MEM_IDNS_QUERY);
}

static void
idnsRead(int fd, void *data)
{
    int *N = data;
    ssize_t len;
    struct sockaddr_in from;
    socklen_t from_len;
    int max = INCOMING_DNS_MAX;
    static char rbuf[SQUID_UDP_SO_RCVBUF];
    int ns;
    while (max--) {
	from_len = sizeof(from);
	memset(&from, '\0', from_len);
	statCounter.syscalls.sock.recvfroms++;
	len = recvfrom(fd, rbuf, 512, 0, (struct sockaddr *) &from, &from_len);
	if (len == 0)
	    break;
	if (len < 0) {
	    if (ignoreErrno(errno))
		break;
#ifdef _SQUID_LINUX_
	    /* Some Linux systems seem to set the FD for reading and then
	     * return ECONNREFUSED when sendto() fails and generates an ICMP
	     * port unreachable message. */
	    /* or maybe an EHOSTUNREACH "No route to host" message */
	    if (errno != ECONNREFUSED && errno != EHOSTUNREACH)
#endif
		debug(50, 1) ("idnsRead: FD %d recvfrom: %s\n",
		    fd, xstrerror());
	    break;
	}
	fd_bytes(DnsSocket, len, FD_READ);
	assert(N);
	(*N)++;
	debug(78, 3) ("idnsRead: FD %d: received %d bytes from %s.\n",
	    fd,
	    len,
	    inet_ntoa(from.sin_addr));
	ns = idnsFromKnownNameserver(&from);
	if (ns >= 0) {
	    nameservers[ns].nreplies++;
	} else if (Config.onoff.ignore_unknown_nameservers) {
	    static time_t last_warning = 0;
	    if (squid_curtime - last_warning > 60) {
		debug(78, 1) ("WARNING: Reply from unknown nameserver [%s]\n",
		    inet_ntoa(from.sin_addr));
		last_warning = squid_curtime;
	    }
	    continue;
	}
	if (len > 512) {
	    /*
	     * Check for non-conforming replies.  RFC 1035 says
	     * DNS/UDP messages must be 512 octets or less.  If we
	     * get one that is too large, we generate a warning
	     * and then pretend that we only got 512 octets.  This
	     * should prevent the rfc1035.c code from reading past
	     * the end of our buffer.
	     */
	    static int other_large_pkts = 0;
	    int x;
	    x = (ns < 0) ? ++other_large_pkts : ++nameservers[ns].large_pkts;
	    if (isPowTen(x))
		debug(78, 1) ("WARNING: Got %d large DNS replies from %s\n",
		    x, inet_ntoa(from.sin_addr));
	    len = 512;
	}
	idnsGrokReply(rbuf, len);
    }
    if (lru_list.head)
	commSetSelect(DnsSocket, COMM_SELECT_READ, idnsRead, NULL, 0);
}

static void
idnsCheckQueue(void *unused)
{
    dlink_node *n;
    dlink_node *p = NULL;
    idns_query *q;
    event_queued = 0;
    for (n = lru_list.tail; n; n = p) {
	if (0 == nns)
	    /* name servers went away; reconfiguring or shutting down */
	    break;
	q = n->data;
	if (tvSubDsec(q->sent_t, current_time) < Config.Timeout.idns_retransmit * (1 << q->nsends % nns))
	    break;
	debug(78, 3) ("idnsCheckQueue: ID %#04x timeout\n",
	    q->id);
	p = n->prev;
	dlinkDelete(&q->lru, &lru_list);
	if (tvSubDsec(q->start_t, current_time) < Config.Timeout.idns_query) {
	    idnsSendQuery(q);
	} else {
	    int v = cbdataValid(q->callback_data);
	    debug(78, 1) ("idnsCheckQueue: ID %x: giving up after %d tries and %5.1f seconds\n",
		(int) q->id, q->nsends,
		tvSubDsec(q->start_t, current_time));
	    cbdataUnlock(q->callback_data);
	    if (v)
		q->callback(q->callback_data, NULL, 0);
	    memFree(q, MEM_IDNS_QUERY);
	}
    }
    idnsTickleQueue();
}

/*
 * rcode < 0 indicates an error, rocde >= 0 indicates success
 */
static void
idnsRcodeCount(int rcode, int attempt)
{
    if (rcode > 0)
	rcode = 0;
    else if (rcode < 0)
	rcode = -rcode;
    if (rcode < MAX_RCODE)
	if (attempt < MAX_ATTEMPT)
	    RcodeMatrix[rcode][attempt]++;
}

/* ====================================================================== */

void
idnsInit(void)
{
    static int init = 0;
    if (DnsSocket < 0) {
	DnsSocket = comm_open(SOCK_DGRAM,
	    0,
	    Config.Addrs.udp_outgoing,
	    0,
	    COMM_NONBLOCKING,
	    "DNS Socket");
	if (DnsSocket < 0)
	    fatal("Could not create a DNS socket");
	debug(78, 1) ("DNS Socket created on FD %d\n", DnsSocket);
    }
    assert(0 == nns);
    idnsParseNameservers();
    if (0 == nns)
	idnsParseResolvConf();
    if (0 == nns)
	fatal("Could not find any nameservers.\n"
	    "       Please check your /etc/resolv.conf file\n"
	    "       or use the 'dns_nameservers' option in squid.conf.");
    if (!init) {
	memDataInit(MEM_IDNS_QUERY, "idns_query", sizeof(idns_query), 0);
	cachemgrRegister("idns",
	    "Internal DNS Statistics",
	    idnsStats, 0, 1);
	memset(RcodeMatrix, '\0', sizeof(RcodeMatrix));
	init++;
    }
}

void
idnsShutdown(void)
{
    if (DnsSocket < 0)
	return;
    comm_close(DnsSocket);
    DnsSocket = -1;
    idnsFreeNameservers();
}

void
idnsALookup(const char *name, IDNSCB * callback, void *data)
{
    idns_query *q = memAllocate(MEM_IDNS_QUERY);
    q->sz = sizeof(q->buf);
    q->id = rfc1035BuildAQuery(name, q->buf, &q->sz);
    if (0 == q->id) {
	/* problem with query data -- query not sent */
	callback(data, NULL, 0);
	memFree(q, MEM_IDNS_QUERY);
	return;
    }
    debug(78, 3) ("idnsALookup: buf is %d bytes for %s, id = %#hx\n",
	(int) q->sz, name, q->id);
    q->callback = callback;
    q->callback_data = data;
    cbdataLock(q->callback_data);
    q->start_t = current_time;
    idnsSendQuery(q);
}

void
idnsPTRLookup(const struct in_addr addr, IDNSCB * callback, void *data)
{
    idns_query *q = memAllocate(MEM_IDNS_QUERY);
    q->sz = sizeof(q->buf);
    q->id = rfc1035BuildPTRQuery(addr, q->buf, &q->sz);
    debug(78, 3) ("idnsPTRLookup: buf is %d bytes for %s, id = %#hx\n",
	(int) q->sz, inet_ntoa(addr), q->id);
    q->callback = callback;
    q->callback_data = data;
    cbdataLock(q->callback_data);
    q->start_t = current_time;
    idnsSendQuery(q);
}

#ifdef SQUID_SNMP
/*
 * The function to return the DNS via SNMP
 */
variable_list *
snmp_netIdnsFn(variable_list * Var, snint * ErrP)
{
    int i, n = 0;
    variable_list *Answer = NULL;
    debug(49, 5) ("snmp_netDnsFn: Processing request:\n", Var->name[LEN_SQ_NET + 1]);
    snmpDebugOid(5, Var->name, Var->name_length);
    *ErrP = SNMP_ERR_NOERROR;
    switch (Var->name[LEN_SQ_NET + 1]) {
    case DNS_REQ:
	for (i = 0; i < nns; i++)
	    n += nameservers[i].nqueries;
	Answer = snmp_var_new_integer(Var->name, Var->name_length,
	    n,
	    SMI_COUNTER32);
	break;
    case DNS_REP:
	for (i = 0; i < nns; i++)
	    n += nameservers[i].nreplies;
	Answer = snmp_var_new_integer(Var->name, Var->name_length,
	    n,
	    SMI_COUNTER32);
	break;
    case DNS_SERVERS:
	Answer = snmp_var_new_integer(Var->name, Var->name_length,
	    0,
	    SMI_COUNTER32);
	break;
    default:
	*ErrP = SNMP_ERR_NOSUCHNAME;
	break;
    }
    return Answer;
}
#endif /*SQUID_SNMP */