text: 
  /*
   * Copyright (C) Igor Sysoev
   */
  
  
  #include <ngx_config.h>
  #include <ngx_core.h>
  #include <ngx_http.h>
  
  
  #define NGX_HTTP_REALIP_XREALIP  0
  #define NGX_HTTP_REALIP_XFWD     1
  #define NGX_HTTP_REALIP_HEADER   2
  
  
  /* AF_INET only */
  
  typedef struct {
      in_addr_t          mask;
      in_addr_t          addr;
  } ngx_http_realip_from_t;
  
  
  typedef struct {
      ngx_array_t       *from;     /* array of ngx_http_realip_from_t */
      ngx_uint_t         type;
      ngx_uint_t         hash;
      ngx_str_t          header;
  } ngx_http_realip_loc_conf_t;
  
  
  typedef struct {
      ngx_connection_t  *connection;
      in_addr_t          addr;
      ngx_str_t          addr_text;
  } ngx_http_realip_ctx_t;
  
  
  static ngx_int_t ngx_http_realip_handler(ngx_http_request_t *r);
  static void ngx_http_realip_cleanup(void *data);
  static char *ngx_http_realip_from(ngx_conf_t *cf, ngx_command_t *cmd,
      void *conf);
  static char *ngx_http_realip(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
  static void *ngx_http_realip_create_loc_conf(ngx_conf_t *cf);
  static char *ngx_http_realip_merge_loc_conf(ngx_conf_t *cf,
      void *parent, void *child);
  static ngx_int_t ngx_http_realip_init(ngx_conf_t *cf);
  
  
  static ngx_command_t  ngx_http_realip_commands[] = {
  
      { ngx_string("set_real_ip_from"),
        NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
        ngx_http_realip_from,
        NGX_HTTP_LOC_CONF_OFFSET,
        0,
        NULL },
  
      { ngx_string("real_ip_header"),
        NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
        ngx_http_realip,
        NGX_HTTP_LOC_CONF_OFFSET,
        0,
        NULL },
  
        ngx_null_command
  };
  
  
  
  static ngx_http_module_t  ngx_http_realip_module_ctx = {
      NULL,                                  /* preconfiguration */
      ngx_http_realip_init,                  /* postconfiguration */
  
      NULL,                                  /* create main configuration */
      NULL,                                  /* init main configuration */
  
      NULL,                                  /* create server configuration */
      NULL,                                  /* merge server configuration */
  
      ngx_http_realip_create_loc_conf,       /* create location configuration */
      ngx_http_realip_merge_loc_conf         /* merge location configuration */
  };
  
  
  ngx_module_t  ngx_http_realip_module = {
      NGX_MODULE_V1,
      &ngx_http_realip_module_ctx,           /* module context */
      ngx_http_realip_commands,              /* module directives */
      NGX_HTTP_MODULE,                       /* module type */
      NULL,                                  /* init master */
      NULL,                                  /* init module */
      NULL,                                  /* init process */
      NULL,                                  /* init thread */
      NULL,                                  /* exit thread */
      NULL,                                  /* exit process */
      NULL,                                  /* exit master */
      NGX_MODULE_V1_PADDING
  };
  
  
  static ngx_int_t
  ngx_http_realip_handler(ngx_http_request_t *r)
  {
      u_char                      *ip, *p;
      size_t                       len;
      in_addr_t                    addr;
      ngx_uint_t                   i, hash;
      ngx_list_part_t             *part;
      ngx_table_elt_t             *header;
      struct sockaddr_in          *sin;
      ngx_connection_t            *c;
      ngx_pool_cleanup_t          *cln;
      ngx_http_realip_ctx_t       *ctx;
      ngx_http_realip_from_t      *from;
      ngx_http_realip_loc_conf_t  *rlcf;
  
      ctx = ngx_http_get_module_ctx(r, ngx_http_realip_module);
  
      if (ctx) {
          return NGX_DECLINED;
      }
  
      cln = ngx_pool_cleanup_add(r->pool, sizeof(ngx_http_realip_ctx_t));
      if (cln == NULL) {
          return NGX_HTTP_INTERNAL_SERVER_ERROR;
      }
  
      rlcf = ngx_http_get_module_loc_conf(r, ngx_http_realip_module);
  
      if (rlcf->from == NULL) {
          return NGX_DECLINED;
      }
  
      switch (rlcf->type) {
  
      case NGX_HTTP_REALIP_XREALIP:
  
          if (r->headers_in.x_real_ip == NULL) {
              return NGX_DECLINED;
          }
  
          len = r->headers_in.x_real_ip->value.len;
          ip = r->headers_in.x_real_ip->value.data;
  
          break;
  
      case NGX_HTTP_REALIP_XFWD:
  
          if (r->headers_in.x_forwarded_for == NULL) {
              return NGX_DECLINED;
          }
  
          len = r->headers_in.x_forwarded_for->value.len;
          ip = r->headers_in.x_forwarded_for->value.data;
  
          for (p = ip + len - 1; p > ip; p--) {
              if (*p == ' ' || *p == ',') {
                  p++;
                  len -= p - ip;
                  ip = p;
                  break;
              }
          }
  
          break;
  
      default: /* NGX_HTTP_REALIP_HEADER */
  
          part = &r->headers_in.headers.part;
          header = part->elts;
  
          hash = rlcf->hash;
          len = rlcf->header.len;
          p = rlcf->header.data;
  
          for (i = 0; /* void */ ; i++) {
  
              if (i >= part->nelts) {
                  if (part->next == NULL) {
                      break;
                  }
  
                  part = part->next;
                  header = part->elts;
                  i = 0;
              }
  
              if (hash == header[i].hash
                  && len == header[i].key.len
                  && ngx_strncmp(p, header[i].lowcase_key, len) == 0)
              {
                  len = header[i].value.len;
                  ip = header[i].value.data;
  
                  goto found;
              }
          }
  
          return NGX_DECLINED;
      }
  
  found:
  
      c = r->connection;
  
      ngx_log_debug1(NGX_LOG_DEBUG_HTTP, c->log, 0, "realip: \"%s\"", ip);
  
      /* AF_INET only */
  
      sin = (struct sockaddr_in *) c->sockaddr;
  
      from = rlcf->from->elts;
      for (i = 0; i < rlcf->from->nelts; i++) {
  
          ngx_log_debug3(NGX_LOG_DEBUG_HTTP, c->log, 0,
                         "realip: %08XD %08XD %08XD",
                         sin->sin_addr.s_addr, from[i].mask, from[i].addr);
  
          if ((sin->sin_addr.s_addr & from[i].mask) == from[i].addr) {
  
              ctx = cln->data;
  
              ngx_http_set_ctx(r, ctx, ngx_http_realip_module);
  
              addr = inet_addr((char *) ip);
  
              if (addr == INADDR_NONE) {
                  return NGX_DECLINED;
              }
  
              p = ngx_pnalloc(c->pool, len);
              if (p == NULL) {
                  return NGX_HTTP_INTERNAL_SERVER_ERROR;
              }
  
              ngx_memcpy(p, ip, len);
  
              cln->handler = ngx_http_realip_cleanup;
  
              ctx->connection = c;
              ctx->addr = sin->sin_addr.s_addr;
              ctx->addr_text = c->addr_text;
  
              sin->sin_addr.s_addr = addr;
  
              c->addr_text.len = len;
              c->addr_text.data = p;
  
              return NGX_DECLINED;
          }
      }
  
      return NGX_DECLINED;
  }
  
  
  static void
  ngx_http_realip_cleanup(void *data)
  {
      ngx_http_realip_ctx_t *ctx = data;
  
      ngx_connection_t    *c;
      struct sockaddr_in  *sin;
  
      c = ctx->connection;
  
      sin = (struct sockaddr_in *) c->sockaddr;
      sin->sin_addr.s_addr = ctx->addr;
  
      c->addr_text = ctx->addr_text;
  }
  
  
  static char *
  ngx_http_realip_from(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
  {
      ngx_http_realip_loc_conf_t *rlcf = conf;
  
      ngx_int_t                rc;
      ngx_str_t               *value;
      ngx_inet_cidr_t          in_cidr;
      ngx_http_realip_from_t  *from;
  
      if (rlcf->from == NULL) {
          rlcf->from = ngx_array_create(cf->pool, 2,
                                        sizeof(ngx_http_realip_from_t));
          if (rlcf->from == NULL) {
              return NGX_CONF_ERROR;
          }
      }
  
      from = ngx_array_push(rlcf->from);
      if (from == NULL) {
          return NGX_CONF_ERROR;
      }
  
      value = cf->args->elts;
  
      rc = ngx_ptocidr(&value[1], &in_cidr);
  
      if (rc == NGX_ERROR) {
          ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "invalid parameter \"%V\"",
                             &value[1]);
          return NGX_CONF_ERROR;
      }
  
      if (rc == NGX_DONE) {
          ngx_conf_log_error(NGX_LOG_WARN, cf, 0,
                             "low address bits of %V are meaningless", &value[1]);
      }
  
      from->mask = in_cidr.mask;
      from->addr = in_cidr.addr;
  
      return NGX_CONF_OK;
  }
  
  
  static char *
  ngx_http_realip(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
  {
      ngx_http_realip_loc_conf_t *rlcf = conf;
  
      ngx_str_t  *value;
  
      value = cf->args->elts;
  
      if (ngx_strcmp(value[1].data, "X-Real-IP") == 0) {
          rlcf->type = NGX_HTTP_REALIP_XREALIP;
          return NGX_CONF_OK;
      }
  
      if (ngx_strcmp(value[1].data, "X-Forwarded-For") == 0) {
          rlcf->type = NGX_HTTP_REALIP_XFWD;
          return NGX_CONF_OK;
      }
  
      rlcf->type = NGX_HTTP_REALIP_HEADER;
      rlcf->hash = ngx_hash_strlow(value[1].data, value[1].data, value[1].len);
      rlcf->header = value[1];
  
      return NGX_CONF_OK;
  }
  
  
  static void *
  ngx_http_realip_create_loc_conf(ngx_conf_t *cf)
  {
      ngx_http_realip_loc_conf_t  *conf;
  
      conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_realip_loc_conf_t));
      if (conf == NULL) {
          return NGX_CONF_ERROR;
      }
  
      /*
       * set by ngx_pcalloc():
       *
       *     conf->from = NULL;
       *     conf->hash = 0;
       *     conf->header = { 0, NULL };
       */
  
      conf->type = NGX_CONF_UNSET_UINT;
  
      return conf;
  }
  
  
  static char *
  ngx_http_realip_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
  {
      ngx_http_realip_loc_conf_t  *prev = parent;
      ngx_http_realip_loc_conf_t  *conf = child;
  
      if (conf->from == NULL) {
          conf->from = prev->from;
      }
  
      ngx_conf_merge_uint_value(conf->type, prev->type, NGX_HTTP_REALIP_XREALIP);
  
      if (conf->header.len == 0) {
          conf->hash = prev->hash;
          conf->header = prev->header;
      }
  
      return NGX_CONF_OK;
  }
  
  
  static ngx_int_t
  ngx_http_realip_init(ngx_conf_t *cf)
  {
      ngx_http_handler_pt        *h;
      ngx_http_core_main_conf_t  *cmcf;
  
      cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);
  
      h = ngx_array_push(&cmcf->phases[NGX_HTTP_POST_READ_PHASE].handlers);
      if (h == NULL) {
          return NGX_ERROR;
      }
  
      *h = ngx_http_realip_handler;
  
      h = ngx_array_push(&cmcf->phases[NGX_HTTP_PREACCESS_PHASE].handlers);
      if (h == NULL) {
          return NGX_ERROR;
      }
  
      *h = ngx_http_realip_handler;
  
      return NGX_OK;
  }
  