src/lib-dict/dict-memcached.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING memcached */

#include "lib.h"
#include "array.h"
#include "str.h"
#include "istream.h"
#include "ostream.h"
#include "connection.h"
#include "dict-private.h"

#define MEMCACHED_DEFAULT_PORT 11211
#define MEMCACHED_DEFAULT_LOOKUP_TIMEOUT_MSECS (1000*30)

/* we need only very limited memcached functionality, so just define the binary
   protocol ourself instead requiring protocol_binary.h */
#define MEMCACHED_REQUEST_HDR_MAGIC 0x80
#define MEMCACHED_REPLY_HDR_MAGIC 0x81

#define MEMCACHED_REQUEST_HDR_LENGTH 24
#define MEMCACHED_REPLY_HDR_LENGTH 24

#define MEMCACHED_CMD_GET 0x00

#define MEMCACHED_DATA_TYPE_RAW 0x00

enum memcached_response {
    MEMCACHED_RESPONSE_OK       = 0x0000,
    MEMCACHED_RESPONSE_NOTFOUND = 0x0001,
    MEMCACHED_RESPONSE_INTERNALERROR= 0x0084,
    MEMCACHED_RESPONSE_BUSY     = 0x0085,
    MEMCACHED_RESPONSE_TEMPFAILURE  = 0x0086,
};

struct memcached_connection {
    struct connection conn;
    struct memcached_dict *dict;

    buffer_t *cmd;
    struct {
        const unsigned char *value;
        size_t value_len;
        uint16_t status; /* enum memcached_response */
        bool reply_received;
    } reply;
};

struct memcached_dict {
    struct dict dict;
    struct ip_addr ip;
    char *key_prefix;
    in_port_t port;
    unsigned int timeout_msecs;

    struct ioloop *ioloop;
    struct memcached_connection conn;

    bool connected;
};

static struct connection_list *memcached_connections;

static void memcached_conn_destroy(struct connection *_conn)
{
    struct memcached_connection *conn = (struct memcached_connection *)_conn;

    conn->dict->connected = FALSE;
    connection_disconnect(_conn);

    if (conn->dict->ioloop != NULL)
        io_loop_stop(conn->dict->ioloop);
}

static int memcached_input_get(struct memcached_connection *conn)
{
    const unsigned char *data;
    size_t size;
    uint32_t body_len, value_pos;
    uint16_t key_len, key_pos, status;
    uint8_t extras_len, data_type;

    data = i_stream_get_data(conn->conn.input, &size);
    if (size < MEMCACHED_REPLY_HDR_LENGTH)
        return 0;

    if (data[0] != MEMCACHED_REPLY_HDR_MAGIC) {
        i_error("memcached: Invalid reply magic: %u != %u",
            data[0], MEMCACHED_REPLY_HDR_MAGIC);
        return -1;
    }
    memcpy(&body_len, data+8, 4); body_len = ntohl(body_len);
    body_len += MEMCACHED_REPLY_HDR_LENGTH;
    if (size < body_len) {
        /* we haven't read the whole response yet */
        return 0;
    }

    memcpy(&key_len, data+2, 2); key_len = ntohs(key_len);
    extras_len = data[4];
    data_type = data[5];
    memcpy(&status, data+6, 2); status = ntohs(status);
    if (data_type != MEMCACHED_DATA_TYPE_RAW) {
        i_error("memcached: Unsupported data type: %u != %u",
            data[0], MEMCACHED_DATA_TYPE_RAW);
        return -1;
    }

    key_pos = MEMCACHED_REPLY_HDR_LENGTH + extras_len;
    value_pos = key_pos + key_len;
    if (value_pos > body_len) {
        i_error("memcached: Invalid key/extras lengths");
        return -1;
    }
    conn->reply.value = data + value_pos;
    conn->reply.value_len = body_len - value_pos;
    conn->reply.status = status;

    i_stream_skip(conn->conn.input, body_len);
    conn->reply.reply_received = TRUE;

    if (conn->dict->ioloop != NULL)
        io_loop_stop(conn->dict->ioloop);
    return 1;
}

static void memcached_conn_input(struct connection *_conn)
{
    struct memcached_connection *conn = (struct memcached_connection *)_conn;

    switch (i_stream_read(_conn->input)) {
    case 0:
        return;
    case -1:
        memcached_conn_destroy(_conn);
        return;
    default:
        break;
    }

    if (memcached_input_get(conn) < 0)
        memcached_conn_destroy(_conn);
}

static void memcached_conn_connected(struct connection *_conn, bool success)
{
    struct memcached_connection *conn =
        (struct memcached_connection *)_conn;

    if (!success) {
        i_error("memcached: connect(%s, %u) failed: %m",
            net_ip2addr(&conn->dict->ip), conn->dict->port);
    } else {
        conn->dict->connected = TRUE;
    }
    if (conn->dict->ioloop != NULL)
        io_loop_stop(conn->dict->ioloop);
}

static const struct connection_settings memcached_conn_set = {
    .input_max_size = (size_t)-1,
    .output_max_size = (size_t)-1,
    .client = TRUE
};

static const struct connection_vfuncs memcached_conn_vfuncs = {
    .destroy = memcached_conn_destroy,
    .input = memcached_conn_input,
    .client_connected = memcached_conn_connected
};

static int
memcached_dict_init(struct dict *driver, const char *uri,
            const struct dict_settings *set ATTR_UNUSED,
            struct dict **dict_r, const char **error_r)
{
    struct memcached_dict *dict;
    const char *const *args;
    int ret = 0;

    if (memcached_connections == NULL) {
        memcached_connections =
            connection_list_init(&memcached_conn_set,
                         &memcached_conn_vfuncs);
    }

    dict = i_new(struct memcached_dict, 1);
    if (net_addr2ip("127.0.0.1", &dict->ip) < 0)
        i_unreached();
    dict->port = MEMCACHED_DEFAULT_PORT;
    dict->timeout_msecs = MEMCACHED_DEFAULT_LOOKUP_TIMEOUT_MSECS;
    dict->key_prefix = i_strdup("");

    args = t_strsplit(uri, ":");
    for (; *args != NULL; args++) {
        if (strncmp(*args, "host=", 5) == 0) {
            if (net_addr2ip(*args+5, &dict->ip) < 0) {
                *error_r = t_strdup_printf("Invalid IP: %s",
                               *args+5);
                ret = -1;
            }
        } else if (strncmp(*args, "port=", 5) == 0) {
            if (net_str2port(*args+5, &dict->port) < 0) {
                *error_r = t_strdup_printf("Invalid port: %s",
                               *args+5);
                ret = -1;
            }
        } else if (strncmp(*args, "prefix=", 7) == 0) {
            i_free(dict->key_prefix);
            dict->key_prefix = i_strdup(*args + 7);
        } else if (strncmp(*args, "timeout_msecs=", 14) == 0) {
            if (str_to_uint(*args+14, &dict->timeout_msecs) < 0) {
                *error_r = t_strdup_printf(
                    "Invalid timeout_msecs: %s", *args+14);
                ret = -1;
            }
        } else {
            *error_r = t_strdup_printf("Unknown parameter: %s",
                           *args);
            ret = -1;
        }
    }
    if (ret < 0) {
        i_free(dict->key_prefix);
        i_free(dict);
        return -1;
    }

    connection_init_client_ip(memcached_connections, &dict->conn.conn,
                  &dict->ip, dict->port);
    dict->dict = *driver;
    dict->conn.cmd = buffer_create_dynamic(default_pool, 256);
    dict->conn.dict = dict;
    *dict_r = &dict->dict;
    return 0;
}

static void memcached_dict_deinit(struct dict *_dict)
{
    struct memcached_dict *dict = (struct memcached_dict *)_dict;

    connection_deinit(&dict->conn.conn);
    buffer_free(&dict->conn.cmd);
    i_free(dict->key_prefix);
    i_free(dict);

    if (memcached_connections->connections == NULL)
        connection_list_deinit(&memcached_connections);
}

static void memcached_dict_lookup_timeout(struct memcached_dict *dict)
{
    i_error("memcached: Lookup timed out in %u.%03u secs",
        dict->timeout_msecs/1000, dict->timeout_msecs%1000);
    io_loop_stop(dict->ioloop);
}

static void memcached_add_header(buffer_t *buf, unsigned int key_len)
{
    uint32_t body_len = htonl(key_len);

    i_assert(key_len <= 0xffff);

    buffer_append_c(buf, MEMCACHED_REQUEST_HDR_MAGIC);
    buffer_append_c(buf, MEMCACHED_CMD_GET);
    buffer_append_c(buf, (key_len >> 8) & 0xff);
    buffer_append_c(buf, key_len & 0xff);
    buffer_append_c(buf, 0); /* extras length */
    buffer_append_c(buf, MEMCACHED_DATA_TYPE_RAW);
    buffer_append_zero(buf, 2); /* vbucket id - we probably don't care? */
    buffer_append(buf, &body_len, sizeof(body_len));
    buffer_append_zero(buf, 4+8); /* opaque + cas */
    i_assert(buf->used == MEMCACHED_REQUEST_HDR_LENGTH);
}

static int
memcached_dict_lookup(struct dict *_dict, pool_t pool, const char *key,
              const char **value_r, const char **error_r)
{
    struct memcached_dict *dict = (struct memcached_dict *)_dict;
    struct ioloop *prev_ioloop = current_ioloop;
    struct timeout *to;
    size_t key_len;

    if (strncmp(key, DICT_PATH_SHARED, strlen(DICT_PATH_SHARED)) == 0)
        key += strlen(DICT_PATH_SHARED);
    else {
        *error_r = t_strdup_printf("memcached: Only shared keys supported currently");
        return -1;
    }
    if (*dict->key_prefix != '\0')
        key = t_strconcat(dict->key_prefix, key, NULL);
    key_len = strlen(key);
    if (key_len > 0xffff) {
        *error_r = t_strdup_printf(
            "memcached: Key is too long (%"PRIuSIZE_T" bytes): %s", key_len, key);
        return -1;
    }

    i_assert(dict->ioloop == NULL);

    dict->ioloop = io_loop_create();
    connection_switch_ioloop(&dict->conn.conn);

    if (dict->conn.conn.fd_in == -1 &&
        connection_client_connect(&dict->conn.conn) < 0) {
        i_error("memcached: Couldn't connect to %s:%u",
            net_ip2addr(&dict->ip), dict->port);
    } else {
        to = timeout_add(dict->timeout_msecs,
                 memcached_dict_lookup_timeout, dict);
        if (!dict->connected) {
            /* wait for connection */
            io_loop_run(dict->ioloop);
        }

        if (dict->connected) {
            buffer_set_used_size(dict->conn.cmd, 0);
            memcached_add_header(dict->conn.cmd, key_len);
            buffer_append(dict->conn.cmd, key, key_len);

            o_stream_nsend(dict->conn.conn.output,
                       dict->conn.cmd->data,
                       dict->conn.cmd->used);

            i_zero(&dict->conn.reply);
            io_loop_run(dict->ioloop);
        }
        timeout_remove(&to);
    }

    io_loop_set_current(prev_ioloop);
    connection_switch_ioloop(&dict->conn.conn);
    io_loop_set_current(dict->ioloop);
    io_loop_destroy(&dict->ioloop);

    if (!dict->conn.reply.reply_received) {
        /* we failed in some way. make sure we disconnect since the
           connection state isn't known anymore */
        memcached_conn_destroy(&dict->conn.conn);
        *error_r = "memcached: Communication failure";
        return -1;
    }
    switch (dict->conn.reply.status) {
    case MEMCACHED_RESPONSE_OK:
        *value_r = p_strndup(pool, dict->conn.reply.value,
                     dict->conn.reply.value_len);
        return 1;
    case MEMCACHED_RESPONSE_NOTFOUND:
        return 0;
    case MEMCACHED_RESPONSE_INTERNALERROR:
        *error_r = "memcached: Lookup failed: Internal error";
        return -1;
    case MEMCACHED_RESPONSE_BUSY:
        *error_r = "memcached: Lookup failed: Busy";
        return -1;
    case MEMCACHED_RESPONSE_TEMPFAILURE:
        *error_r = "memcached: Lookup failed: Temporary failure";
        return -1;
    }

    *error_r = t_strdup_printf("memcached: Lookup failed: Error code=%u",
                   dict->conn.reply.status);
    return -1;
}

struct dict dict_driver_memcached = {
    .name = "memcached",
    {
        .init = memcached_dict_init,
        .deinit = memcached_dict_deinit,
        .lookup = memcached_dict_lookup,
    }
};