text: #include "base.h"
  #include "log.h"
  #include "buffer.h"
  
  #include "plugin.h"
  
  #include "inet_ntop_cache.h"
  
  #include <ctype.h>
  #include <stdlib.h>
  #include <string.h>
  
  /**
   * mod_evasive
   *
   * we indent to implement all features the mod_evasive from apache has
   *
   * - limit of connections per IP
   * - provide a list of block-listed ip/networks (no access)
   * - provide a white-list of ips/network which is not affected by the limit
   *   (hmm, conditionals might be enough)
   * - provide a bandwidth limiter per IP
   *
   * started by:
   * - w1zzard@techpowerup.com
   */
  
  typedef struct {
  	unsigned short max_conns;
  	unsigned short silent;
  } plugin_config;
  
  typedef struct {
  	PLUGIN_DATA;
  
  	plugin_config **config_storage;
  
  	plugin_config conf;
  } plugin_data;
  
  INIT_FUNC(mod_evasive_init) {
  	plugin_data *p;
  
  	p = calloc(1, sizeof(*p));
  
  	return p;
  }
  
  FREE_FUNC(mod_evasive_free) {
  	plugin_data *p = p_d;
  
  	UNUSED(srv);
  
  	if (!p) return HANDLER_GO_ON;
  
  	if (p->config_storage) {
  		size_t i;
  		for (i = 0; i < srv->config_context->used; i++) {
  			plugin_config *s = p->config_storage[i];
  
  			if (NULL == s) continue;
  
  			free(s);
  		}
  		free(p->config_storage);
  	}
  
  	free(p);
  
  	return HANDLER_GO_ON;
  }
  
  SETDEFAULTS_FUNC(mod_evasive_set_defaults) {
  	plugin_data *p = p_d;
  	size_t i = 0;
  
  	config_values_t cv[] = {
  		{ "evasive.max-conns-per-ip",    NULL, T_CONFIG_SHORT, T_CONFIG_SCOPE_CONNECTION },   /* 0 */
  		{ "evasive.silent",              NULL, T_CONFIG_BOOLEAN, T_CONFIG_SCOPE_CONNECTION }, /* 1 */
  		{ NULL,                          NULL, T_CONFIG_UNSET, T_CONFIG_SCOPE_UNSET }
  	};
  
  	p->config_storage = calloc(1, srv->config_context->used * sizeof(plugin_config *));
  
  	for (i = 0; i < srv->config_context->used; i++) {
  		data_config const* config = (data_config const*)srv->config_context->data[i];
  		plugin_config *s;
  
  		s = calloc(1, sizeof(plugin_config));
  		s->max_conns       = 0;
  		s->silent          = 0;
  
  		cv[0].destination = &(s->max_conns);
  		cv[1].destination = &(s->silent);
  
  		p->config_storage[i] = s;
  
  		if (0 != config_insert_values_global(srv, config->value, cv, i == 0 ? T_CONFIG_SCOPE_SERVER : T_CONFIG_SCOPE_CONNECTION)) {
  			return HANDLER_ERROR;
  		}
  	}
  
  	return HANDLER_GO_ON;
  }
  
  #define PATCH(x) \
  	p->conf.x = s->x;
  static int mod_evasive_patch_connection(server *srv, connection *con, plugin_data *p) {
  	size_t i, j;
  	plugin_config *s = p->config_storage[0];
  
  	PATCH(max_conns);
  	PATCH(silent);
  
  	/* skip the first, the global context */
  	for (i = 1; i < srv->config_context->used; i++) {
  		data_config *dc = (data_config *)srv->config_context->data[i];
  		s = p->config_storage[i];
  
  		/* condition didn't match */
  		if (!config_check_cond(srv, con, dc)) continue;
  
  		/* merge config */
  		for (j = 0; j < dc->value->used; j++) {
  			data_unset *du = dc->value->data[j];
  
  			if (buffer_is_equal_string(du->key, CONST_STR_LEN("evasive.max-conns-per-ip"))) {
  				PATCH(max_conns);
  			} else if (buffer_is_equal_string(du->key, CONST_STR_LEN("evasive.silent"))) {
  				PATCH(silent);
  			}
  		}
  	}
  
  	return 0;
  }
  #undef PATCH
  
  URIHANDLER_FUNC(mod_evasive_uri_handler) {
  	plugin_data *p = p_d;
  	size_t conns_by_ip = 0;
  	size_t j;
  
  	if (buffer_is_empty(con->uri.path)) return HANDLER_GO_ON;
  
  	mod_evasive_patch_connection(srv, con, p);
  
  	/* no limit set, nothing to block */
  	if (p->conf.max_conns == 0) return HANDLER_GO_ON;
  
  	switch (con->dst_addr.plain.sa_family) {
  		case AF_INET:
  #ifdef HAVE_IPV6
  		case AF_INET6:
  #endif
  			break;
  		default: /* Address family not supported */
  			return HANDLER_GO_ON;
  	};
  
  	for (j = 0; j < srv->conns->used; j++) {
  		connection *c = srv->conns->ptr[j];
  
  		/* check if other connections are already actively serving data for the same IP
  		 * we can only ban connections which are already behind the 'read request' state
  		 * */
  		if (c->dst_addr.plain.sa_family != con->dst_addr.plain.sa_family) continue;
  		if (c->state <= CON_STATE_REQUEST_END) continue;
  
  		switch (con->dst_addr.plain.sa_family) {
  			case AF_INET:
  				if (c->dst_addr.ipv4.sin_addr.s_addr != con->dst_addr.ipv4.sin_addr.s_addr) continue;
  				break;
  #ifdef HAVE_IPV6
  			case AF_INET6:
  				if (0 != memcmp(c->dst_addr.ipv6.sin6_addr.s6_addr, con->dst_addr.ipv6.sin6_addr.s6_addr, 16)) continue;
  				break;
  #endif
  			default: /* Address family not supported, should never be reached */
  				continue;
  		};
  		conns_by_ip++;
  
  		if (conns_by_ip > p->conf.max_conns) {
  			if (!p->conf.silent) {
  				log_error_write(srv, __FILE__, __LINE__, "ss",
  					inet_ntop_cache_get_ip(srv, &(con->dst_addr)),
  					"turned away. Too many connections.");
  			}
  
  			con->http_status = 403;
  			con->mode = DIRECT;
  			return HANDLER_FINISHED;
  		}
  	}
  
  	return HANDLER_GO_ON;
  }
  
  
  int mod_evasive_plugin_init(plugin *p);
  int mod_evasive_plugin_init(plugin *p) {
  	p->version     = LIGHTTPD_VERSION_ID;
  	p->name        = buffer_init_string("evasive");
  
  	p->init        = mod_evasive_init;
  	p->set_defaults = mod_evasive_set_defaults;
  	p->handle_uri_clean  = mod_evasive_uri_handler;
  	p->cleanup     = mod_evasive_free;
  
  	p->data        = NULL;
  
  	return 0;
  }
  