fqdncache.cc

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/*
 * Copyright (C) 1996-2021 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
/* DEBUG: section 35    FQDN Cache */
 
#include "squid.h"
#include "cbdata.h"
#include "dns/forward.h"
#include "dns/LookupDetails.h"
#include "dns/rfc1035.h"
#include "event.h"
#include "fqdncache.h"
#include "helper.h"
#include "mgr/Registration.h"
#include "snmp_agent.h"
#include "SquidConfig.h"
#include "SquidTime.h"
#include "StatCounters.h"
#include "Store.h"
#include "util.h"
 
#if SQUID_SNMP
#include "snmp_core.h"
#endif
 
#define FQDN_LOW_WATER       90
 
#define FQDN_HIGH_WATER      95
 
class fqdncache_entry
{
    MEMPROXY_CLASS(fqdncache_entry);
 
public:
    fqdncache_entry(const char *name);
    ~fqdncache_entry();
 
    hash_link hash;     /* must be first */
    time_t lastref;
    time_t expires;
    unsigned char name_count;
    char *names[FQDN_MAX_NAMES + 1];
    FQDNH *handler;
    void *handlerData;
    char *error_message;
 
    struct timeval request_time;
    dlink_node lru;
    unsigned short locks;
 
    struct Flags {
        Flags() : negcached(false), fromhosts(false) {}
 
        bool negcached;
        bool fromhosts;
    } flags;
 
    int age() const; 
};
 
static struct _fqdn_cache_stats {
    int requests;
    int replies;
    int hits;
    int misses;
    int negative_hits;
} FqdncacheStats;
 
static dlink_list lru_list;
 
static IDNSCB fqdncacheHandleReply;
static int fqdncacheParse(fqdncache_entry *, const rfc1035_rr *, int, const char *error_message);
static void fqdncacheRelease(fqdncache_entry *);
static void fqdncacheCallback(fqdncache_entry *, int wait);
static fqdncache_entry *fqdncache_get(const char *);
static int fqdncacheExpiredEntry(const fqdncache_entry *);
static void fqdncacheLockEntry(fqdncache_entry * f);
static void fqdncacheUnlockEntry(fqdncache_entry * f);
static FREE fqdncacheFreeEntry;
static void fqdncacheAddEntry(fqdncache_entry * f);
 
static hash_table *fqdn_table = NULL;
 
static long fqdncache_low = 180;
 
static long fqdncache_high = 200;
 
inline int fqdncacheCount() { return fqdn_table ? fqdn_table->count : 0; }
 
int
fqdncache_entry::age() const
{
    return request_time.tv_sec ? tvSubMsec(request_time, current_time) : -1;
}
 
static void
fqdncacheRelease(fqdncache_entry * f)
{
    hash_remove_link(fqdn_table, (hash_link *) f);
    debugs(35, 5, "fqdncacheRelease: Released FQDN record for '" << hashKeyStr(&f->hash) << "'.");
    dlinkDelete(&f->lru, &lru_list);
    delete f;
}
 
static fqdncache_entry *
fqdncache_get(const char *name)
{
    hash_link *e;
    static fqdncache_entry *f;
    f = NULL;
 
    if (fqdn_table) {
        if ((e = (hash_link *)hash_lookup(fqdn_table, name)) != NULL)
            f = (fqdncache_entry *) e;
    }
 
    return f;
}
 
static int
fqdncacheExpiredEntry(const fqdncache_entry * f)
{
    /* all static entries are locked, so this takes care of them too */
 
    if (f->locks != 0)
        return 0;
 
    if (f->expires > squid_curtime)
        return 0;
 
    return 1;
}
 
void
fqdncache_purgelru(void *)
{
    dlink_node *m;
    dlink_node *prev = NULL;
    fqdncache_entry *f;
    int removed = 0;
    eventAdd("fqdncache_purgelru", fqdncache_purgelru, NULL, 10.0, 1);
 
    for (m = lru_list.tail; m; m = prev) {
        if (fqdncacheCount() < fqdncache_low)
            break;
 
        prev = m->prev;
 
        f = (fqdncache_entry *)m->data;
 
        if (f->locks != 0)
            continue;
 
        fqdncacheRelease(f);
 
        ++removed;
    }
 
    debugs(35, 9, "fqdncache_purgelru: removed " << removed << " entries");
}
 
static void
purge_entries_fromhosts(void)
{
    dlink_node *m = lru_list.head;
    fqdncache_entry *i = NULL;
    fqdncache_entry *t;
 
    while (m) {
        if (i != NULL) {    /* need to delay deletion */
            fqdncacheRelease(i);    /* we just override locks */
            i = NULL;
        }
 
        t = (fqdncache_entry *)m->data;
 
        if (t->flags.fromhosts)
            i = t;
 
        m = m->next;
    }
 
    if (i != NULL)
        fqdncacheRelease(i);
}
 
fqdncache_entry::fqdncache_entry(const char *name) :
    lastref(0),
    expires(squid_curtime + Config.negativeDnsTtl),
    name_count(0),
    handler(nullptr),
    handlerData(nullptr),
    error_message(nullptr),
    locks(0) // XXX: use Lock
{
    hash.key = xstrdup(name);
 
    memset(&request_time, 0, sizeof(request_time));
    memset(&names, 0, sizeof(names));
}
 
static void
fqdncacheAddEntry(fqdncache_entry * f)
{
    hash_link *e = (hash_link *)hash_lookup(fqdn_table, f->hash.key);
 
    if (NULL != e) {
        /* avoid collision */
        fqdncache_entry *q = (fqdncache_entry *) e;
        fqdncacheRelease(q);
    }
 
    hash_join(fqdn_table, &f->hash);
    dlinkAdd(f, &f->lru, &lru_list);
    f->lastref = squid_curtime;
}
 
static void
fqdncacheCallback(fqdncache_entry * f, int wait)
{
    FQDNH *callback;
    void *cbdata;
    f->lastref = squid_curtime;
 
    if (!f->handler)
        return;
 
    fqdncacheLockEntry(f);
 
    callback = f->handler;
 
    f->handler = NULL;
 
    if (cbdataReferenceValidDone(f->handlerData, &cbdata)) {
        const Dns::LookupDetails details(f->error_message, wait);
        callback(f->name_count ? f->names[0] : NULL, details, cbdata);
    }
 
    fqdncacheUnlockEntry(f);
}
 
static int
fqdncacheParse(fqdncache_entry *f, const rfc1035_rr * answers, int nr, const char *error_message)
{
    int k;
    int ttl = 0;
    const char *name = (const char *)f->hash.key;
    f->expires = squid_curtime + Config.negativeDnsTtl;
    f->flags.negcached = true;
 
    if (nr < 0) {
        debugs(35, 3, "fqdncacheParse: Lookup of '" << name << "' failed (" << error_message << ")");
        f->error_message = xstrdup(error_message);
        return -1;
    }
 
    if (nr == 0) {
        debugs(35, 3, "fqdncacheParse: No DNS records for '" << name << "'");
        f->error_message = xstrdup("No DNS records");
        return 0;
    }
 
    debugs(35, 3, "fqdncacheParse: " << nr << " answers for '" << name << "'");
    assert(answers);
 
    for (k = 0; k < nr; ++k) {
        if (answers[k]._class != RFC1035_CLASS_IN)
            continue;
 
        if (answers[k].type == RFC1035_TYPE_PTR) {
            if (!answers[k].rdata[0]) {
                debugs(35, 2, "fqdncacheParse: blank PTR record for '" << name << "'");
                continue;
            }
 
            if (strchr(answers[k].rdata, ' ')) {
                debugs(35, 2, "fqdncacheParse: invalid PTR record '" << answers[k].rdata << "' for '" << name << "'");
                continue;
            }
 
            f->names[f->name_count] = xstrdup(answers[k].rdata);
            ++ f->name_count;
        } else if (answers[k].type != RFC1035_TYPE_CNAME)
            continue;
 
        if (ttl == 0 || (int) answers[k].ttl < ttl)
            ttl = answers[k].ttl;
 
        if (f->name_count >= FQDN_MAX_NAMES)
            break;
    }
 
    if (f->name_count == 0) {
        debugs(35, DBG_IMPORTANT, "fqdncacheParse: No PTR record for '" << name << "'");
        return 0;
    }
 
    if (ttl > Config.positiveDnsTtl)
        ttl = Config.positiveDnsTtl;
 
    if (ttl < Config.negativeDnsTtl)
        ttl = Config.negativeDnsTtl;
 
    f->expires = squid_curtime + ttl;
 
    f->flags.negcached = false;
 
    return f->name_count;
}
 
static void
fqdncacheHandleReply(void *data, const rfc1035_rr * answers, int na, const char *error_message, const bool lastAnswer)
{
    assert(lastAnswer); // reverse DNS lookups do not generate multiple queries
    fqdncache_entry *f;
    static_cast<generic_cbdata *>(data)->unwrap(&f);
    ++FqdncacheStats.replies;
    const int age = f->age();
    statCounter.dns.svcTime.count(age);
    fqdncacheParse(f, answers, na, error_message);
    fqdncacheAddEntry(f);
    fqdncacheCallback(f, age);
}
 
void
fqdncache_nbgethostbyaddr(const Ip::Address &addr, FQDNH * handler, void *handlerData)
{
    fqdncache_entry *f = NULL;
    char name[MAX_IPSTRLEN];
    generic_cbdata *c;
    addr.toStr(name,MAX_IPSTRLEN);
    debugs(35, 4, "fqdncache_nbgethostbyaddr: Name '" << name << "'.");
    ++FqdncacheStats.requests;
 
    if (name[0] == '\0') {
        debugs(35, 4, "fqdncache_nbgethostbyaddr: Invalid name!");
        const Dns::LookupDetails details("Invalid hostname", -1); // error, no lookup
        if (handler)
            handler(NULL, details, handlerData);
        return;
    }
 
    f = fqdncache_get(name);
 
    if (NULL == f) {
        /* miss */
        (void) 0;
    } else if (fqdncacheExpiredEntry(f)) {
        /* hit, but expired -- bummer */
        fqdncacheRelease(f);
        f = NULL;
    } else {
        /* hit */
        debugs(35, 4, "fqdncache_nbgethostbyaddr: HIT for '" << name << "'");
 
        if (f->flags.negcached)
            ++ FqdncacheStats.negative_hits;
        else
            ++ FqdncacheStats.hits;
 
        f->handler = handler;
 
        f->handlerData = cbdataReference(handlerData);
 
        fqdncacheCallback(f, -1); // no lookup
 
        return;
    }
 
    debugs(35, 5, "fqdncache_nbgethostbyaddr: MISS for '" << name << "'");
    ++ FqdncacheStats.misses;
    f = new fqdncache_entry(name);
    f->handler = handler;
    f->handlerData = cbdataReference(handlerData);
    f->request_time = current_time;
    c = new generic_cbdata(f);
    idnsPTRLookup(addr, fqdncacheHandleReply, c);
}
 
const char *
fqdncache_gethostbyaddr(const Ip::Address &addr, int flags)
{
    char name[MAX_IPSTRLEN];
    fqdncache_entry *f = NULL;
 
    if (addr.isAnyAddr() || addr.isNoAddr()) {
        return NULL;
    }
 
    addr.toStr(name,MAX_IPSTRLEN);
    ++ FqdncacheStats.requests;
    f = fqdncache_get(name);
 
    if (NULL == f) {
        (void) 0;
    } else if (fqdncacheExpiredEntry(f)) {
        fqdncacheRelease(f);
        f = NULL;
    } else if (f->flags.negcached) {
        ++ FqdncacheStats.negative_hits;
        // ignore f->error_message: the caller just checks FQDN cache presence
        return NULL;
    } else {
        ++ FqdncacheStats.hits;
        f->lastref = squid_curtime;
        // ignore f->error_message: the caller just checks FQDN cache presence
        return f->names[0];
    }
 
    /* no entry [any more] */
 
    ++ FqdncacheStats.misses;
 
    if (flags & FQDN_LOOKUP_IF_MISS) {
        fqdncache_nbgethostbyaddr(addr, NULL, NULL);
    }
 
    return NULL;
}
 
void
fqdnStats(StoreEntry * sentry)
{
    fqdncache_entry *f = NULL;
    int k;
    int ttl;
 
    if (fqdn_table == NULL)
        return;
 
    storeAppendPrintf(sentry, "FQDN Cache Statistics:\n");
 
    storeAppendPrintf(sentry, "FQDNcache Entries In Use: %d\n",
                      fqdncache_entry::UseCount());
 
    storeAppendPrintf(sentry, "FQDNcache Entries Cached: %d\n",
                      fqdncacheCount());
 
    storeAppendPrintf(sentry, "FQDNcache Requests: %d\n",
                      FqdncacheStats.requests);
 
    storeAppendPrintf(sentry, "FQDNcache Hits: %d\n",
                      FqdncacheStats.hits);
 
    storeAppendPrintf(sentry, "FQDNcache Negative Hits: %d\n",
                      FqdncacheStats.negative_hits);
 
    storeAppendPrintf(sentry, "FQDNcache Misses: %d\n",
                      FqdncacheStats.misses);
 
    storeAppendPrintf(sentry, "FQDN Cache Contents:\n\n");
 
    storeAppendPrintf(sentry, "%-45.45s %3s %3s %3s %s\n",
                      "Address", "Flg", "TTL", "Cnt", "Hostnames");
 
    hash_first(fqdn_table);
 
    while ((f = (fqdncache_entry *) hash_next(fqdn_table))) {
        ttl = (f->flags.fromhosts ? -1 : (f->expires - squid_curtime));
        storeAppendPrintf(sentry, "%-45.45s  %c%c %3.3d % 3d",
                          hashKeyStr(&f->hash),
                          f->flags.negcached ? 'N' : ' ',
                          f->flags.fromhosts ? 'H' : ' ',
                          ttl,
                          (int) f->name_count);
 
        for (k = 0; k < (int) f->name_count; ++k)
            storeAppendPrintf(sentry, " %s", f->names[k]);
 
        storeAppendPrintf(sentry, "\n");
    }
}
 
static void
fqdncacheLockEntry(fqdncache_entry * f)
{
    if (f->locks++ == 0) {
        dlinkDelete(&f->lru, &lru_list);
        dlinkAdd(f, &f->lru, &lru_list);
    }
}
 
static void
fqdncacheUnlockEntry(fqdncache_entry * f)
{
    assert(f->locks > 0);
    -- f->locks;
 
    if (fqdncacheExpiredEntry(f))
        fqdncacheRelease(f);
}
 
static void
fqdncacheFreeEntry(void *data)
{
    fqdncache_entry *f = (fqdncache_entry *)data;
    delete f;
}
 
fqdncache_entry::~fqdncache_entry()
{
    for (int k = 0; k < (int)name_count; ++k)
        xfree(names[k]);
 
    xfree(hash.key);
    xfree(error_message);
}
 
void
fqdncacheFreeMemory(void)
{
    hashFreeItems(fqdn_table, fqdncacheFreeEntry);
    hashFreeMemory(fqdn_table);
    fqdn_table = NULL;
}
 
void
fqdncache_restart(void)
{
    fqdncache_high = (long) (((float) Config.fqdncache.size *
                              (float) FQDN_HIGH_WATER) / (float) 100);
    fqdncache_low = (long) (((float) Config.fqdncache.size *
                             (float) FQDN_LOW_WATER) / (float) 100);
    purge_entries_fromhosts();
}
 
void
fqdncacheAddEntryFromHosts(char *addr, SBufList &hostnames)
{
    fqdncache_entry *fce= fqdncache_get(addr);
    if (fce) {
        if (1 == fce->flags.fromhosts) {
            fqdncacheUnlockEntry(fce);
        } else if (fce->locks > 0) {
            debugs(35, DBG_IMPORTANT, "WARNING: can't add static entry for locked address '" << addr << "'");
            return;
        } else {
            fqdncacheRelease(fce);
        }
    }
 
    fce = new fqdncache_entry(addr);
 
    int j = 0;
    for (auto &h : hostnames) {
        fce->names[j] = xstrdup(h.c_str());
        Tolower(fce->names[j]);
        ++j;
 
        if (j >= FQDN_MAX_NAMES)
            break;
    }
 
    fce->name_count = j;
    fce->names[j] = NULL;   /* it's safe */
    fce->flags.fromhosts = true;
    fqdncacheAddEntry(fce);
    fqdncacheLockEntry(fce);
}
 
static void
fqdncacheRegisterWithCacheManager(void)
{
    Mgr::RegisterAction("fqdncache", "FQDN Cache Stats and Contents",
                        fqdnStats, 0, 1);
 
}
 
void
fqdncache_init(void)
{
    int n;
 
    fqdncacheRegisterWithCacheManager();
 
    if (fqdn_table)
        return;
 
    debugs(35, 3, "Initializing FQDN Cache...");
 
    memset(&FqdncacheStats, '\0', sizeof(FqdncacheStats));
    lru_list = dlink_list();
 
    fqdncache_high = (long) (((float) Config.fqdncache.size *
                              (float) FQDN_HIGH_WATER) / (float) 100);
 
    fqdncache_low = (long) (((float) Config.fqdncache.size *
                             (float) FQDN_LOW_WATER) / (float) 100);
 
    n = hashPrime(fqdncache_high / 4);
 
    fqdn_table = hash_create((HASHCMP *) strcmp, n, hash4);
}
 
#if SQUID_SNMP
 
variable_list *
snmp_netFqdnFn(variable_list * Var, snint * ErrP)
{
    variable_list *Answer = NULL;
    MemBuf tmp;
    debugs(49, 5, "snmp_netFqdnFn: Processing request:" << snmpDebugOid(Var->name, Var->name_length, tmp));
    *ErrP = SNMP_ERR_NOERROR;
 
    switch (Var->name[LEN_SQ_NET + 1]) {
 
    case FQDN_ENT:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      fqdncacheCount(),
                                      SMI_GAUGE32);
        break;
 
    case FQDN_REQ:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      FqdncacheStats.requests,
                                      SMI_COUNTER32);
        break;
 
    case FQDN_HITS:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      FqdncacheStats.hits,
                                      SMI_COUNTER32);
        break;
 
    case FQDN_PENDHIT:
        /* this is now worthless */
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      0,
                                      SMI_GAUGE32);
        break;
 
    case FQDN_NEGHIT:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      FqdncacheStats.negative_hits,
                                      SMI_COUNTER32);
        break;
 
    case FQDN_MISS:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      FqdncacheStats.misses,
                                      SMI_COUNTER32);
        break;
 
    case FQDN_GHBN:
        Answer = snmp_var_new_integer(Var->name, Var->name_length,
                                      0, /* deprecated */
                                      SMI_COUNTER32);
        break;
 
    default:
        *ErrP = SNMP_ERR_NOSUCHNAME;
        break;
    }
 
    return Answer;
}
 
#endif /*SQUID_SNMP */