new file mode 100644
--- /dev/null
+++ b/src/http/modules/ngx_http_userid_filter.c
@@ -0,0 +1,588 @@
+
+/*
+ * Copyright (C) Igor Sysoev
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_http.h>
+
+
+#define NGX_HTTP_USERID_OFF   0
+#define NGX_HTTP_USERID_LOG   1
+#define NGX_HTTP_USERID_V1    2
+#define NGX_HTTP_USERID_ON    3
+
+/* 31 Dec 2037 23:55:55 GMT */
+#define NGX_HTTP_USERID_MAX_EXPIRES  2145916555
+
+
+typedef struct {
+    ngx_flag_t  enable;
+
+    ngx_int_t   service;
+
+    ngx_str_t   name;
+    ngx_str_t   domain;
+    ngx_str_t   path;
+    time_t      expires;
+
+    ngx_int_t   p3p;
+    ngx_str_t   p3p_string;
+} ngx_http_userid_conf_t;
+
+
+typedef struct {
+    uint32_t          uid_got[4];
+    uint32_t          uid_set[4];
+} ngx_http_userid_ctx_t;
+
+
+static ngx_int_t ngx_http_userid_get_uid(ngx_http_request_t *r,
+                                         ngx_http_userid_ctx_t *ctx,
+                                         ngx_http_userid_conf_t *conf);
+static ngx_int_t ngx_http_userid_set_uid(ngx_http_request_t *r,
+                                         ngx_http_userid_ctx_t *ctx,
+                                         ngx_http_userid_conf_t *conf);
+
+static u_char *ngx_http_userid_log_uid_got(ngx_http_request_t *r, u_char *buf,
+                                           uintptr_t data);
+static u_char *ngx_http_userid_log_uid_set(ngx_http_request_t *r, u_char *buf,
+                                           uintptr_t data);
+
+static ngx_int_t ngx_http_userid_init(ngx_cycle_t *cycle);
+static ngx_int_t ngx_http_userid_pre_conf(ngx_conf_t *cf);
+static void *ngx_http_userid_create_conf(ngx_conf_t *cf);
+static char *ngx_http_userid_merge_conf(ngx_conf_t *cf, void *parent,
+                                        void *child);
+char *ngx_conf_check_domain(ngx_conf_t *cf, void *post, void *data);
+char *ngx_http_userid_expires(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
+
+
+static uint32_t  sequencer_v1 = 1;
+static uint32_t  sequencer_v2 = 0x03030302;
+
+
+static u_char expires[] = "; expires=Thu, 31-Dec-37 23:55:55 GMT";
+
+
+static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
+
+
+static ngx_conf_enum_t  ngx_http_userid_state[] = {
+    { ngx_string("off"), NGX_HTTP_USERID_OFF },
+    { ngx_string("log"), NGX_HTTP_USERID_LOG },
+    { ngx_string("v1"), NGX_HTTP_USERID_V1 },
+    { ngx_string("on"), NGX_HTTP_USERID_ON },
+    { ngx_null_string, 0 }
+};
+
+
+static ngx_conf_post_handler_pt  ngx_conf_check_domain_p =
+                                                         ngx_conf_check_domain;
+
+
+static ngx_command_t  ngx_http_userid_commands[] = {
+
+    { ngx_string("userid"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_conf_set_enum_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_userid_conf_t, enable),
+      ngx_http_userid_state },
+
+    { ngx_string("userid_service"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_num_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_userid_conf_t, service),
+      NULL },
+
+    { ngx_string("userid_name"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_str_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_userid_conf_t, name),
+      NULL },
+
+    { ngx_string("userid_domain"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_str_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_userid_conf_t, domain),
+      &ngx_conf_check_domain_p },
+
+    { ngx_string("userid_path"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
+      ngx_conf_set_str_slot,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      offsetof(ngx_http_userid_conf_t, path),
+      NULL },
+
+    { ngx_string("userid_expires"),
+      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
+      ngx_http_userid_expires,
+      NGX_HTTP_LOC_CONF_OFFSET,
+      0,
+      NULL },
+
+    ngx_null_command
+};
+
+
+ngx_http_module_t  ngx_http_userid_filter_module_ctx = {
+    ngx_http_userid_pre_conf,              /* pre conf */
+
+    NULL,                                  /* create main configuration */
+    NULL,                                  /* init main configuration */
+
+    NULL,                                  /* create server configuration */
+    NULL,                                  /* merge server configuration */
+
+    ngx_http_userid_create_conf,           /* create location configration */
+    ngx_http_userid_merge_conf             /* merge location configration */
+};
+
+
+ngx_module_t  ngx_http_userid_filter_module = {
+    NGX_MODULE,
+    &ngx_http_userid_filter_module_ctx,    /* module context */
+    ngx_http_userid_commands,              /* module directives */
+    NGX_HTTP_MODULE,                       /* module type */
+    ngx_http_userid_init,                  /* init module */
+    NULL                                   /* init process */
+};
+
+
+static ngx_http_log_op_name_t ngx_http_userid_log_fmt_ops[] = {
+    { ngx_string("uid_got"), 0, ngx_http_userid_log_uid_got },
+    { ngx_string("uid_set"), 0, ngx_http_userid_log_uid_set },
+    { ngx_null_string, 0, NULL }
+};
+
+
+static ngx_int_t ngx_http_userid_filter(ngx_http_request_t *r)
+{
+    ngx_int_t                rc;
+    ngx_http_userid_ctx_t   *ctx;
+    ngx_http_userid_conf_t  *conf;
+
+    conf = ngx_http_get_module_loc_conf(r, ngx_http_userid_filter_module);
+
+    if (conf->enable == NGX_HTTP_USERID_OFF) {
+        return ngx_http_next_header_filter(r);
+    }
+
+    ngx_http_create_ctx(r, ctx, ngx_http_userid_filter_module,
+                        sizeof(ngx_http_userid_ctx_t), NGX_ERROR);
+
+    rc = ngx_http_userid_get_uid(r, ctx, conf);
+
+    if (rc != NGX_OK) {
+        return rc;
+    }
+
+    if (conf->enable == NGX_HTTP_USERID_LOG || ctx->uid_got[3] != 0) {
+        return ngx_http_next_header_filter(r);
+    }
+
+    rc = ngx_http_userid_set_uid(r, ctx, conf);
+
+    if (rc != NGX_OK) {
+        return rc;
+    }
+
+    return ngx_http_next_header_filter(r);
+}
+
+
+static ngx_int_t ngx_http_userid_get_uid(ngx_http_request_t *r,
+                                         ngx_http_userid_ctx_t *ctx,
+                                         ngx_http_userid_conf_t *conf)
+{
+    u_char            *start, *last, *end;
+    ngx_uint_t         i;
+    ngx_str_t          src, dst;
+    ngx_table_elt_t  **cookies;
+
+    cookies = r->headers_in.cookies.elts;
+
+    for (i = 0; i < r->headers_in.cookies.nelts; i++) {
+        ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                       "cookie: \"%s\"", cookies[i]->value.data);
+
+        end = cookies[i]->value.data + cookies[i]->value.len;
+
+        for (start = cookies[i]->value.data; start < end; /* void */) {
+
+            if (conf->name.len >= cookies[i]->value.len
+                || ngx_strncmp(start, conf->name.data, conf->name.len) != 0)
+            {
+                start += conf->name.len;
+                while (start < end && *start++ != ';') { /* void */ }
+
+                for (/* void */; start < end && *start == ' '; start++) { /**/ }
+
+                continue;
+            }
+
+            for (start += conf->name.len; start < end && *start == ' '; start++)
+            {
+                /* void */
+            }
+
+            if (*start != '=') {
+                break;
+            }
+
+            for (start++; start < end && *start == ' '; start++) { /* void */ }
+
+            for (last = start; last < end && *last != ';'; last++) { /**/ }
+
+            if (last - start < 22) {
+                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                              "client sent too short userid cookie \"%s\"",
+                              cookies[i]->value.data);
+                break;
+            }
+
+            /*
+             * we have to limit encoded string to 22 characters
+             * because there are already the millions cookies with a garbage
+             * instead of the correct base64 trail "=="
+             */
+
+            src.len = 22;
+            src.data = start;
+            dst.data = (u_char *) ctx->uid_got;
+
+            if (ngx_decode_base64(&src, &dst) == NGX_ERROR) {
+                ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
+                              "client sent invalid userid cookie \"%s\"",
+                              cookies[i]->value.data);
+                break;
+            }
+
+            ngx_log_debug4(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                           "uid: %08X%08X%08X%08X",
+                           ctx->uid_got[0], ctx->uid_got[1],
+                           ctx->uid_got[2], ctx->uid_got[3]);
+
+            return NGX_OK;
+        }
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t ngx_http_userid_set_uid(ngx_http_request_t *r,
+                                         ngx_http_userid_ctx_t *ctx,
+                                         ngx_http_userid_conf_t *conf)
+
+{
+    u_char              *cookie, *p;
+    size_t               len;
+    socklen_t            slen;
+    struct sockaddr_in   addr_in;
+    ngx_str_t            src, dst;
+    ngx_table_elt_t     *set_cookie;
+
+    /* TODO: mutex for sequencers */
+
+    if (conf->enable == NGX_HTTP_USERID_V1) {
+        if (conf->service == NGX_CONF_UNSET) {
+            ctx->uid_set[0] = 0;
+        } else {
+            ctx->uid_set[0] = htonl(conf->service);
+        }
+
+        ctx->uid_set[1] = ngx_time();
+        ctx->uid_set[2] = ngx_pid;
+        ctx->uid_set[3] = sequencer_v1;
+        sequencer_v1 += 0x100;
+
+    } else {
+        if (conf->service == NGX_CONF_UNSET) {
+            if (r->in_addr == 0) {
+                slen = sizeof(struct sockaddr_in);
+                if (getsockname(r->connection->fd,
+                                (struct sockaddr *) &addr_in, &slen) == -1)
+                {
+                    ngx_log_error(NGX_LOG_CRIT, r->connection->log,
+                                  ngx_socket_errno,
+                                  "getsockname() failed");
+                }
+
+                r->in_addr = addr_in.sin_addr.s_addr;
+            }
+
+            ctx->uid_set[0] = htonl(r->in_addr);
+
+        } else {
+            ctx->uid_set[0] = htonl(conf->service);
+        }
+
+        ctx->uid_set[1] = htonl(ngx_time());
+        ctx->uid_set[2] = htonl(ngx_pid);
+        ctx->uid_set[3] = htonl(sequencer_v2);
+        sequencer_v2 += 0x100;
+        if (sequencer_v2 < 0x03030302) {
+            sequencer_v2 = 0x03030302;
+        }
+    }
+
+    len = conf->name.len + 1 + ngx_base64_encoded_length(16) + 1;
+
+    if (conf->expires) {
+        len += sizeof(expires) - 1 + 2;
+    }
+
+    if (conf->domain.len > 1) {
+        len += sizeof("; domain=") - 1 + conf->domain.len;
+    }
+
+    if (conf->path.len) {
+        len += sizeof("; path=") - 1 + conf->path.len;
+    }
+
+    if (!(cookie = ngx_palloc(r->pool, len))) {
+        return NGX_ERROR;
+    }
+
+    p = ngx_cpymem(cookie, conf->name.data, conf->name.len);
+    *p++ = '=';
+
+    src.len = 16;
+    src.data = (u_char *) ctx->uid_set;
+    dst.data = p;
+
+    ngx_encode_base64(&src, &dst);
+
+    p += dst.len;
+
+    if (conf->expires == NGX_HTTP_USERID_MAX_EXPIRES) {
+        p = ngx_cpymem(p, expires, sizeof(expires) - 1);
+
+    } else if (conf->expires) {
+        p = ngx_cpymem(p, expires, sizeof("; expires=") - 1);
+        p += ngx_http_cookie_time(p, ngx_time() + conf->expires);
+    }
+
+    if (conf->domain.len > 1) {
+        p = ngx_cpymem(p, "; domain=", sizeof("; domain=") - 1);
+        p = ngx_cpymem(p, conf->domain.data, conf->domain.len);
+    }
+
+    if (conf->path.len) {
+        p = ngx_cpymem(p, "; path=", sizeof("; path=") - 1);
+        p = ngx_cpymem(p, conf->path.data, conf->path.len);
+    }
+
+    *p = '\0';
+
+    ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
+                   "uid cookie: \"%s\"", cookie);
+
+    if (!(set_cookie = ngx_list_push(&r->headers_out.headers))) {
+        return NGX_ERROR;
+    }
+
+    set_cookie->key.len = sizeof("Set-Cookie") - 1;
+    set_cookie->key.data = (u_char *) "Set-Cookie";
+    set_cookie->value.len = p - cookie;
+    set_cookie->value.data = cookie;
+
+    return NGX_OK;
+}
+
+
+static u_char *ngx_http_userid_log_uid_got(ngx_http_request_t *r, u_char *buf,
+                                           uintptr_t data)
+{
+    ngx_http_userid_ctx_t   *ctx;
+    ngx_http_userid_conf_t  *conf;
+
+    ctx = ngx_http_get_module_ctx(r, ngx_http_userid_filter_module);
+
+    if (ctx == NULL || ctx->uid_got[3] == 0) {
+        if (buf == NULL) {
+            return (u_char *) 1;
+        }
+
+        *buf = '-';
+        return buf + 1;
+    }
+
+    conf = ngx_http_get_module_loc_conf(r, ngx_http_userid_filter_module);
+
+    if (buf == NULL) {
+        return (u_char *) (conf->name.len + 1 + 32);
+    }
+
+    buf = ngx_cpymem(buf, conf->name.data, conf->name.len);
+
+    *buf++ = '=';
+
+    return buf + ngx_snprintf((char *) buf, 33, "%08X%08X%08X%08X",
+                              ctx->uid_got[0], ctx->uid_got[1],
+                              ctx->uid_got[2], ctx->uid_got[3]);
+}
+
+
+static u_char *ngx_http_userid_log_uid_set(ngx_http_request_t *r, u_char *buf,
+                                           uintptr_t data)
+{
+    ngx_http_userid_ctx_t   *ctx;
+    ngx_http_userid_conf_t  *conf;
+
+    ctx = ngx_http_get_module_ctx(r, ngx_http_userid_filter_module);
+
+    if (ctx == NULL || ctx->uid_set[3] == 0) {
+        if (buf == NULL) {
+            return (u_char *) 1;
+        }
+
+        *buf = '-';
+        return buf + 1;
+    }
+
+    conf = ngx_http_get_module_loc_conf(r, ngx_http_userid_filter_module);
+
+    if (buf == NULL) {
+        return (u_char *) (conf->name.len + 1 + 32);
+    }
+
+    buf = ngx_cpymem(buf, conf->name.data, conf->name.len);
+
+    *buf++ = '=';
+
+    return buf + ngx_snprintf((char *) buf, 33, "%08X%08X%08X%08X",
+                              ctx->uid_set[0], ctx->uid_set[1],
+                              ctx->uid_set[2], ctx->uid_set[3]);
+}
+
+
+static ngx_int_t ngx_http_userid_init(ngx_cycle_t *cycle)
+{
+    ngx_http_next_header_filter = ngx_http_top_header_filter;
+    ngx_http_top_header_filter = ngx_http_userid_filter;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t ngx_http_userid_pre_conf(ngx_conf_t *cf)
+{
+    ngx_http_log_op_name_t  *op;
+
+    for (op = ngx_http_userid_log_fmt_ops; op->name.len; op++) { /* void */ }
+    op->op = NULL;
+
+    op = ngx_http_log_fmt_ops;
+
+    for (op = ngx_http_log_fmt_ops; op->op; op++) {
+        if (op->name.len == 0) {
+            op = (ngx_http_log_op_name_t *) op->op;
+        }
+    }
+
+    op->op = (ngx_http_log_op_pt) ngx_http_userid_log_fmt_ops;
+
+    return NGX_OK;
+}
+
+
+static void *ngx_http_userid_create_conf(ngx_conf_t *cf)
+{   
+    ngx_http_userid_conf_t  *conf;
+
+    if (!(conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_userid_conf_t)))) {
+        return NGX_CONF_ERROR;
+    }
+
+    /* set by ngx_pcalloc():
+
+    conf->name.len = 0;
+    conf->name.date = NULL;
+    conf->domain.len = 0;
+    conf->domain.date = NULL;
+    conf->path.len = 0;
+    conf->path.date = NULL;
+
+    */
+
+    conf->enable = NGX_CONF_UNSET;
+    conf->service = NGX_CONF_UNSET;
+    conf->expires = NGX_CONF_UNSET;
+
+    return conf;
+}   
+
+
+static char *ngx_http_userid_merge_conf(ngx_conf_t *cf, void *parent,
+                                        void *child)
+{
+    ngx_http_userid_conf_t *prev = parent;
+    ngx_http_userid_conf_t *conf = child;
+
+    ngx_conf_merge_value(conf->enable, prev->enable, NGX_HTTP_USERID_OFF);
+
+    ngx_conf_merge_str_value(conf->name, prev->name, "uid");
+    ngx_conf_merge_str_value(conf->domain, prev->domain, ".");
+    ngx_conf_merge_str_value(conf->path, prev->path, "/");
+
+    ngx_conf_merge_value(conf->service, prev->service, NGX_CONF_UNSET);
+    ngx_conf_merge_sec_value(conf->expires, prev->expires, 0);
+
+    return NGX_CONF_OK;
+}
+
+
+char *ngx_conf_check_domain(ngx_conf_t *cf, void *post, void *data)
+{
+    ngx_str_t  *domain = data;
+
+    if (domain->len == 4 && ngx_strcmp(domain->data, "none") == 0) {
+        domain->len = 1;
+        domain->data = (u_char *) ".";
+    }
+
+    return NGX_CONF_OK;
+}
+
+
+char *ngx_http_userid_expires(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
+{
+    ngx_http_userid_conf_t *ucf = conf;
+
+    ngx_str_t   *value;
+
+    if (ucf->expires != NGX_CONF_UNSET) {
+        return "is duplicate";
+    }
+
+    value = cf->args->elts;
+
+    if (ngx_strcmp(value[1].data, "max") == 0) {
+        ucf->expires = NGX_HTTP_USERID_MAX_EXPIRES;
+        return NGX_CONF_OK;
+    }
+
+    if (ngx_strcmp(value[1].data, "off") == 0) {
+        ucf->expires = 0;
+        return NGX_CONF_OK;
+    }
+
+    ucf->expires = ngx_parse_time(&value[1], 1);
+    if (ucf->expires == NGX_ERROR) {
+        return "invalid value";
+    }
+
+    if (ucf->expires == NGX_PARSE_LARGE_TIME) {
+        return "value must be less than 68 years";
+    }
+
+    return NGX_CONF_OK;
+}