/*
* cachedb/redis.c - cachedb redis module
*
* Copyright (c) 2018, NLnet Labs. All rights reserved.
*
* This software is open source.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the NLNET LABS nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* \file
*
* This file contains a module that uses the redis database to cache
* dns responses.
*/
#include "config.h"
#ifdef USE_CACHEDB
#include "cachedb/redis.h"
#include "cachedb/cachedb.h"
#include "util/alloc.h"
#include "util/config_file.h"
#include "sldns/sbuffer.h"
#ifdef USE_REDIS
#include "hiredis/hiredis.h"
struct redis_moddata {
redisContext** ctxs; /* thread-specific redis contexts */
int numctxs; /* number of ctx entries */
const char* server_host; /* server's IP address or host name */
int server_port; /* server's TCP port */
struct timeval timeout; /* timeout for connection setup and commands */
};
static redisContext*
redis_connect(const struct redis_moddata* moddata)
{
redisContext* ctx;
ctx = redisConnectWithTimeout(moddata->server_host,
moddata->server_port, moddata->timeout);
if(!ctx || ctx->err) {
const char *errstr = "out of memory";
if(ctx)
errstr = ctx->errstr;
log_err("failed to connect to redis server: %s", errstr);
goto fail;
}
if(redisSetTimeout(ctx, moddata->timeout) != REDIS_OK) {
log_err("failed to set redis timeout");
goto fail;
}
return ctx;
fail:
if(ctx)
redisFree(ctx);
return NULL;
}
static int
redis_init(struct module_env* env, struct cachedb_env* cachedb_env)
{
int i;
struct redis_moddata* moddata = NULL;
verbose(VERB_ALGO, "redis_init");
moddata = calloc(1, sizeof(struct redis_moddata));
if(!moddata) {
log_err("out of memory");
return 0;
}
moddata->numctxs = env->cfg->num_threads;
moddata->ctxs = calloc(env->cfg->num_threads, sizeof(redisContext*));
if(!moddata->ctxs) {
log_err("out of memory");
free(moddata);
return 0;
}
/* note: server_host is a shallow reference to configured string.
* we don't have to free it in this module. */
moddata->server_host = env->cfg->redis_server_host;
moddata->server_port = env->cfg->redis_server_port;
moddata->timeout.tv_sec = env->cfg->redis_timeout / 1000;
moddata->timeout.tv_usec = (env->cfg->redis_timeout % 1000) * 1000;
for(i = 0; i < moddata->numctxs; i++)
moddata->ctxs[i] = redis_connect(moddata);
cachedb_env->backend_data = moddata;
return 1;
}
static void
redis_deinit(struct module_env* env, struct cachedb_env* cachedb_env)
{
struct redis_moddata* moddata = (struct redis_moddata*)
cachedb_env->backend_data;
(void)env;
verbose(VERB_ALGO, "redis_deinit");
if(!moddata)
return;
if(moddata->ctxs) {
int i;
for(i = 0; i < moddata->numctxs; i++) {
if(moddata->ctxs[i])
redisFree(moddata->ctxs[i]);
}
free(moddata->ctxs);
}
free(moddata);
}
/*
* Send a redis command and get a reply. Unified so that it can be used for
* both SET and GET. If 'data' is non-NULL the command is supposed to be
* SET and GET otherwise, but the implementation of this function is agnostic
* about the semantics (except for logging): 'command', 'data', and 'data_len'
* are opaquely passed to redisCommand().
* This function first checks whether a connection with a redis server has
* been established; if not it tries to set up a new one.
* It returns redisReply returned from redisCommand() or NULL if some low
* level error happens. The caller is responsible to check the return value,
* if it's non-NULL, it has to free it with freeReplyObject().
*/
static redisReply*
redis_command(struct module_env* env, struct cachedb_env* cachedb_env,
const char* command, const uint8_t* data, size_t data_len)
{
redisContext* ctx;
redisReply* rep;
struct redis_moddata* d = (struct redis_moddata*)
cachedb_env->backend_data;
/* We assume env->alloc->thread_num is a unique ID for each thread
* in [0, num-of-threads). We could treat it as an error condition
* if the assumption didn't hold, but it seems to be a fundamental
* assumption throughout the unbound architecture, so we simply assert
* it. */
log_assert(env->alloc->thread_num < d->numctxs);
ctx = d->ctxs[env->alloc->thread_num];
/* If we've not established a connection to the server or we've closed
* it on a failure, try to re-establish a new one. Failures will be
* logged in redis_connect(). */
if(!ctx) {
ctx = redis_connect(d);
d->ctxs[env->alloc->thread_num] = ctx;
}
if(!ctx)
return NULL;
/* Send the command and get a reply, synchronously. */
rep = (redisReply*)redisCommand(ctx, command, data, data_len);
if(!rep) {
/* Once an error as a NULL-reply is returned the context cannot
* be reused and we'll need to set up a new connection. */
log_err("redis_command: failed to receive a reply, "
"closing connection: %s", ctx->errstr);
redisFree(ctx);
d->ctxs[env->alloc->thread_num] = NULL;
return NULL;
}
/* Check error in reply to unify logging in that case.
* The caller may perform context-dependent checks and logging. */
if(rep->type == REDIS_REPLY_ERROR)
log_err("redis: %s resulted in an error: %s",
data ? "set" : "get", rep->str);
return rep;
}
static int
redis_lookup(struct module_env* env, struct cachedb_env* cachedb_env,
char* key, struct sldns_buffer* result_buffer)
{
redisReply* rep;
char cmdbuf[4+(CACHEDB_HASHSIZE/8)*2+1]; /* "GET " + key */
int n;
int ret = 0;
verbose(VERB_ALGO, "redis_lookup of %s", key);
n = snprintf(cmdbuf, sizeof(cmdbuf), "GET %s", key);
if(n < 0 || n >= (int)sizeof(cmdbuf)) {
log_err("redis_lookup: unexpected failure to build command");
return 0;
}
rep = redis_command(env, cachedb_env, cmdbuf, NULL, 0);
if(!rep)
return 0;
switch (rep->type) {
case REDIS_REPLY_NIL:
verbose(VERB_ALGO, "redis_lookup: no data cached");
break;
case REDIS_REPLY_STRING:
verbose(VERB_ALGO, "redis_lookup found %d bytes",
(int)rep->len);
if((size_t)rep->len > sldns_buffer_capacity(result_buffer)) {
log_err("redis_lookup: replied data too long: %lu",
(size_t)rep->len);
break;
}
sldns_buffer_clear(result_buffer);
sldns_buffer_write(result_buffer, rep->str, rep->len);
sldns_buffer_flip(result_buffer);
ret = 1;
break;
case REDIS_REPLY_ERROR:
break; /* already logged */
default:
log_err("redis_lookup: unexpected type of reply for (%d)",
rep->type);
break;
}
freeReplyObject(rep);
return ret;
}
static void
redis_store(struct module_env* env, struct cachedb_env* cachedb_env,
char* key, uint8_t* data, size_t data_len)
{
redisReply* rep;
char cmdbuf[4+(CACHEDB_HASHSIZE/8)*2+3+1]; /* "SET " + key + " %b" */
int n;
verbose(VERB_ALGO, "redis_store %s (%d bytes)", key, (int)data_len);
/* build command to set to a binary safe string */
n = snprintf(cmdbuf, sizeof(cmdbuf), "SET %s %%b", key);
if(n < 0 || n >= (int)sizeof(cmdbuf)) {
log_err("redis_store: unexpected failure to build command");
return;
}
rep = redis_command(env, cachedb_env, cmdbuf, data, data_len);
if(rep) {
verbose(VERB_ALGO, "redis_store set completed");
if(rep->type != REDIS_REPLY_STATUS &&
rep->type != REDIS_REPLY_ERROR) {
log_err("redis_store: unexpected type of reply (%d)",
rep->type);
}
freeReplyObject(rep);
}
}
struct cachedb_backend redis_backend = { "redis",
redis_init, redis_deinit, redis_lookup, redis_store
};
#endif /* USE_REDIS */
#endif /* USE_CACHEDB */