new file mode 100644
--- /dev/null
+++ b/src/event/quic/ngx_event_quic_connid.c
@@ -0,0 +1,532 @@
+
+/*
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_event_quic_connection.h>
+
+
+#define NGX_QUIC_MAX_SERVER_IDS   8
+
+
+static ngx_int_t ngx_quic_create_server_id(ngx_connection_t *c, u_char *id);
+#if (NGX_QUIC_BPF)
+static ngx_int_t ngx_quic_bpf_attach_id(ngx_connection_t *c, u_char *id);
+#endif
+static ngx_int_t ngx_quic_retire_connection_id(ngx_connection_t *c,
+    enum ssl_encryption_level_t level, uint64_t seqnum);
+static ngx_quic_server_id_t *ngx_quic_insert_server_id(ngx_connection_t *c,
+    ngx_quic_connection_t *qc, ngx_str_t *id);
+static ngx_quic_client_id_t *ngx_quic_alloc_client_id(ngx_connection_t *c,
+    ngx_quic_connection_t *qc);
+static ngx_quic_server_id_t *ngx_quic_alloc_server_id(ngx_connection_t *c,
+    ngx_quic_connection_t *qc);
+
+
+ngx_int_t
+ngx_quic_setup_connection_ids(ngx_connection_t *c, ngx_quic_connection_t *qc,
+    ngx_quic_header_t *pkt)
+{
+    ngx_quic_server_id_t   *sid, *osid;
+    ngx_quic_client_id_t   *cid;
+
+    /*
+     * qc->nclient_ids = 0
+     * qc->nserver_ids = 0
+     * qc->max_retired_seqnum = 0
+     */
+
+    ngx_queue_init(&qc->client_ids);
+    ngx_queue_init(&qc->server_ids);
+    ngx_queue_init(&qc->free_client_ids);
+    ngx_queue_init(&qc->free_server_ids);
+
+    qc->odcid.len = pkt->odcid.len;
+    qc->odcid.data = ngx_pstrdup(c->pool, &pkt->odcid);
+    if (qc->odcid.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    qc->tp.original_dcid = qc->odcid;
+
+    qc->scid.len = pkt->scid.len;
+    qc->scid.data = ngx_pstrdup(c->pool, &pkt->scid);
+    if (qc->scid.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    qc->dcid.len = NGX_QUIC_SERVER_CID_LEN;
+    qc->dcid.data = ngx_pnalloc(c->pool, qc->dcid.len);
+    if (qc->dcid.data == NULL) {
+        return NGX_ERROR;
+    }
+
+    if (ngx_quic_create_server_id(c, qc->dcid.data) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    qc->tp.initial_scid = qc->dcid;
+
+    cid = ngx_quic_alloc_client_id(c, qc);
+    if (cid == NULL) {
+        return NGX_ERROR;
+    }
+
+    cid->seqnum = 0;
+    cid->len = pkt->scid.len;
+    ngx_memcpy(cid->id, pkt->scid.data, pkt->scid.len);
+
+    ngx_queue_insert_tail(&qc->client_ids, &cid->queue);
+    qc->nclient_ids++;
+    qc->client_seqnum = 0;
+
+    qc->server_seqnum = NGX_QUIC_UNSET_PN;
+
+    osid = ngx_quic_insert_server_id(c, qc, &qc->odcid);
+    if (osid == NULL) {
+        return NGX_ERROR;
+    }
+
+    qc->server_seqnum = 0;
+
+    sid = ngx_quic_insert_server_id(c, qc, &qc->dcid);
+    if (sid == NULL) {
+        ngx_rbtree_delete(&c->listening->rbtree, &osid->udp.node);
+        return NGX_ERROR;
+    }
+
+    c->udp = &sid->udp;
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_quic_create_server_id(ngx_connection_t *c, u_char *id)
+{
+    if (RAND_bytes(id, NGX_QUIC_SERVER_CID_LEN) != 1) {
+        return NGX_ERROR;
+    }
+
+#if (NGX_QUIC_BPF)
+    if (ngx_quic_bpf_attach_id(c, id) != NGX_OK) {
+        ngx_log_error(NGX_LOG_ERR, c->log, 0,
+                      "quic bpf failed to generate socket key");
+        /* ignore error, things still may work */
+    }
+#endif
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic create server id %*xs",
+                   (size_t) NGX_QUIC_SERVER_CID_LEN, id);
+    return NGX_OK;
+}
+
+
+#if (NGX_QUIC_BPF)
+
+static ngx_int_t
+ngx_quic_bpf_attach_id(ngx_connection_t *c, u_char *id)
+{
+    int        fd;
+    uint64_t   cookie;
+    socklen_t  optlen;
+
+    fd = c->listening->fd;
+
+    optlen = sizeof(cookie);
+
+    if (getsockopt(fd, SOL_SOCKET, SO_COOKIE, &cookie, &optlen) == -1) {
+        ngx_log_error(NGX_LOG_ERR, c->log, ngx_socket_errno,
+                      "quic getsockopt(SO_COOKIE) failed");
+
+        return NGX_ERROR;
+    }
+
+    ngx_quic_dcid_encode_key(id, cookie);
+
+    return NGX_OK;
+}
+
+#endif
+
+
+
+
+ngx_int_t
+ngx_quic_handle_new_connection_id_frame(ngx_connection_t *c,
+    ngx_quic_header_t *pkt, ngx_quic_new_conn_id_frame_t *f)
+{
+    ngx_queue_t            *q;
+    ngx_quic_client_id_t   *cid, *item;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    if (f->seqnum < qc->max_retired_seqnum) {
+        /*
+         *  An endpoint that receives a NEW_CONNECTION_ID frame with
+         *  a sequence number smaller than the Retire Prior To field
+         *  of a previously received NEW_CONNECTION_ID frame MUST send
+         *  a corresponding RETIRE_CONNECTION_ID frame that retires
+         *  the newly received connection  ID, unless it has already
+         *  done so for that sequence number.
+         */
+
+        if (ngx_quic_retire_connection_id(c, pkt->level, f->seqnum) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        goto retire;
+    }
+
+    cid = NULL;
+
+    for (q = ngx_queue_head(&qc->client_ids);
+         q != ngx_queue_sentinel(&qc->client_ids);
+         q = ngx_queue_next(q))
+    {
+        item = ngx_queue_data(q, ngx_quic_client_id_t, queue);
+
+        if (item->seqnum == f->seqnum) {
+            cid = item;
+            break;
+        }
+    }
+
+    if (cid) {
+        /*
+         * Transmission errors, timeouts and retransmissions might cause the
+         * same NEW_CONNECTION_ID frame to be received multiple times
+         */
+
+        if (cid->len != f->len
+            || ngx_strncmp(cid->id, f->cid, f->len) != 0
+            || ngx_strncmp(cid->sr_token, f->srt, NGX_QUIC_SR_TOKEN_LEN) != 0)
+        {
+            /*
+             * ..a sequence number is used for different connection IDs,
+             * the endpoint MAY treat that receipt as a connection error
+             * of type PROTOCOL_VIOLATION.
+             */
+            qc->error = NGX_QUIC_ERR_PROTOCOL_VIOLATION;
+            qc->error_reason = "seqnum refers to different connection id/token";
+            return NGX_ERROR;
+        }
+
+    } else {
+
+        cid = ngx_quic_alloc_client_id(c, qc);
+        if (cid == NULL) {
+            return NGX_ERROR;
+        }
+
+        cid->seqnum = f->seqnum;
+        cid->len = f->len;
+        ngx_memcpy(cid->id, f->cid, f->len);
+
+        ngx_memcpy(cid->sr_token, f->srt, NGX_QUIC_SR_TOKEN_LEN);
+
+        ngx_queue_insert_tail(&qc->client_ids, &cid->queue);
+        qc->nclient_ids++;
+
+        /* always use latest available connection id */
+        if (f->seqnum > qc->client_seqnum) {
+            qc->scid.len = cid->len;
+            qc->scid.data = cid->id;
+            qc->client_seqnum = f->seqnum;
+        }
+    }
+
+retire:
+
+    if (qc->max_retired_seqnum && f->retire <= qc->max_retired_seqnum) {
+        /*
+         * Once a sender indicates a Retire Prior To value, smaller values sent
+         * in subsequent NEW_CONNECTION_ID frames have no effect.  A receiver
+         * MUST ignore any Retire Prior To fields that do not increase the
+         * largest received Retire Prior To value.
+         */
+        goto done;
+    }
+
+    qc->max_retired_seqnum = f->retire;
+
+    q = ngx_queue_head(&qc->client_ids);
+
+    while (q != ngx_queue_sentinel(&qc->client_ids)) {
+
+        cid = ngx_queue_data(q, ngx_quic_client_id_t, queue);
+        q = ngx_queue_next(q);
+
+        if (cid->seqnum >= f->retire) {
+            continue;
+        }
+
+        /* this connection id must be retired */
+
+        if (ngx_quic_retire_connection_id(c, pkt->level, cid->seqnum)
+            != NGX_OK)
+        {
+            return NGX_ERROR;
+        }
+
+        ngx_queue_remove(&cid->queue);
+        ngx_queue_insert_head(&qc->free_client_ids, &cid->queue);
+        qc->nclient_ids--;
+    }
+
+done:
+
+    if (qc->nclient_ids > qc->tp.active_connection_id_limit) {
+        /*
+         * After processing a NEW_CONNECTION_ID frame and
+         * adding and retiring active connection IDs, if the number of active
+         * connection IDs exceeds the value advertised in its
+         * active_connection_id_limit transport parameter, an endpoint MUST
+         * close the connection with an error of type CONNECTION_ID_LIMIT_ERROR.
+         */
+        qc->error = NGX_QUIC_ERR_CONNECTION_ID_LIMIT_ERROR;
+        qc->error_reason = "too many connection ids received";
+        return NGX_ERROR;
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_quic_retire_connection_id(ngx_connection_t *c,
+    enum ssl_encryption_level_t level, uint64_t seqnum)
+{
+    ngx_quic_frame_t       *frame;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    frame = ngx_quic_alloc_frame(c);
+    if (frame == NULL) {
+        return NGX_ERROR;
+    }
+
+    frame->level = level;
+    frame->type = NGX_QUIC_FT_RETIRE_CONNECTION_ID;
+    frame->u.retire_cid.sequence_number = seqnum;
+
+    ngx_quic_queue_frame(qc, frame);
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
+ngx_quic_handle_retire_connection_id_frame(ngx_connection_t *c,
+    ngx_quic_header_t *pkt, ngx_quic_retire_cid_frame_t *f)
+{
+    ngx_queue_t            *q;
+    ngx_quic_server_id_t   *sid;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    for (q = ngx_queue_head(&qc->server_ids);
+         q != ngx_queue_sentinel(&qc->server_ids);
+         q = ngx_queue_next(q))
+    {
+        sid = ngx_queue_data(q, ngx_quic_server_id_t, queue);
+
+        if (sid->seqnum == f->sequence_number) {
+            ngx_queue_remove(q);
+            ngx_queue_insert_tail(&qc->free_server_ids, &sid->queue);
+            ngx_rbtree_delete(&c->listening->rbtree, &sid->udp.node);
+            qc->nserver_ids--;
+            break;
+        }
+    }
+
+    return ngx_quic_issue_server_ids(c);
+}
+
+
+ngx_int_t
+ngx_quic_issue_server_ids(ngx_connection_t *c)
+{
+    ngx_str_t               dcid;
+    ngx_uint_t              n;
+    ngx_quic_frame_t       *frame;
+    ngx_quic_server_id_t   *sid;
+    ngx_quic_connection_t  *qc;
+    u_char                  id[NGX_QUIC_SERVER_CID_LEN];
+
+    qc = ngx_quic_get_connection(c);
+
+    n = ngx_min(NGX_QUIC_MAX_SERVER_IDS, qc->ctp.active_connection_id_limit);
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic issue server ids has:%ui max:%ui", qc->nserver_ids, n);
+
+    while (qc->nserver_ids < n) {
+        if (ngx_quic_create_server_id(c, id) != NGX_OK) {
+            return NGX_ERROR;
+        }
+
+        dcid.len = NGX_QUIC_SERVER_CID_LEN;
+        dcid.data = id;
+
+        sid = ngx_quic_insert_server_id(c, qc, &dcid);
+        if (sid == NULL) {
+            return NGX_ERROR;
+        }
+
+        frame = ngx_quic_alloc_frame(c);
+        if (frame == NULL) {
+            return NGX_ERROR;
+        }
+
+        frame->level = ssl_encryption_application;
+        frame->type = NGX_QUIC_FT_NEW_CONNECTION_ID;
+        frame->u.ncid.seqnum = sid->seqnum;
+        frame->u.ncid.retire = 0;
+        frame->u.ncid.len = NGX_QUIC_SERVER_CID_LEN;
+        ngx_memcpy(frame->u.ncid.cid, id, NGX_QUIC_SERVER_CID_LEN);
+
+        if (ngx_quic_new_sr_token(c, &dcid, qc->conf->sr_token_key,
+                                  frame->u.ncid.srt)
+            != NGX_OK)
+        {
+            return NGX_ERROR;
+        }
+
+        ngx_quic_queue_frame(qc, frame);
+    }
+
+    return NGX_OK;
+}
+
+
+void
+ngx_quic_clear_temp_server_ids(ngx_connection_t *c)
+{
+    ngx_queue_t            *q, *next;
+    ngx_quic_server_id_t   *sid;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic clear temp server ids");
+
+    for (q = ngx_queue_head(&qc->server_ids);
+         q != ngx_queue_sentinel(&qc->server_ids);
+         q = next)
+    {
+        next = ngx_queue_next(q);
+        sid = ngx_queue_data(q, ngx_quic_server_id_t, queue);
+
+        if (sid->seqnum != NGX_QUIC_UNSET_PN) {
+            continue;
+        }
+
+        ngx_queue_remove(q);
+        ngx_queue_insert_tail(&qc->free_server_ids, &sid->queue);
+        ngx_rbtree_delete(&c->listening->rbtree, &sid->udp.node);
+        qc->nserver_ids--;
+    }
+}
+
+
+static ngx_quic_server_id_t *
+ngx_quic_insert_server_id(ngx_connection_t *c, ngx_quic_connection_t *qc,
+    ngx_str_t *id)
+{
+    ngx_str_t              dcid;
+    ngx_quic_server_id_t  *sid;
+
+    sid = ngx_quic_alloc_server_id(c, qc);
+    if (sid == NULL) {
+        return NULL;
+    }
+
+    sid->quic = qc;
+
+    sid->seqnum = qc->server_seqnum;
+
+    if (qc->server_seqnum != NGX_QUIC_UNSET_PN) {
+        qc->server_seqnum++;
+    }
+
+    sid->len = id->len;
+    ngx_memcpy(sid->id, id->data, id->len);
+
+    ngx_queue_insert_tail(&qc->server_ids, &sid->queue);
+    qc->nserver_ids++;
+
+    dcid.data = sid->id;
+    dcid.len = sid->len;
+
+    ngx_insert_udp_connection(c, &sid->udp, &dcid);
+
+    ngx_log_debug3(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic insert server id seqnum:%uL id len:%uz %xV",
+                   sid->seqnum, id->len, id);
+
+    return sid;
+}
+
+
+static ngx_quic_client_id_t *
+ngx_quic_alloc_client_id(ngx_connection_t *c, ngx_quic_connection_t *qc)
+{
+    ngx_queue_t           *q;
+    ngx_quic_client_id_t  *cid;
+
+    if (!ngx_queue_empty(&qc->free_client_ids)) {
+
+        q = ngx_queue_head(&qc->free_client_ids);
+        cid = ngx_queue_data(q, ngx_quic_client_id_t, queue);
+
+        ngx_queue_remove(&cid->queue);
+
+        ngx_memzero(cid, sizeof(ngx_quic_client_id_t));
+
+    } else {
+
+        cid = ngx_pcalloc(c->pool, sizeof(ngx_quic_client_id_t));
+        if (cid == NULL) {
+            return NULL;
+        }
+    }
+
+    return cid;
+}
+
+
+static ngx_quic_server_id_t *
+ngx_quic_alloc_server_id(ngx_connection_t *c, ngx_quic_connection_t *qc)
+{
+    ngx_queue_t           *q;
+    ngx_quic_server_id_t  *sid;
+
+    if (!ngx_queue_empty(&qc->free_server_ids)) {
+
+        q = ngx_queue_head(&qc->free_server_ids);
+        sid = ngx_queue_data(q, ngx_quic_server_id_t, queue);
+
+        ngx_queue_remove(&sid->queue);
+
+        ngx_memzero(sid, sizeof(ngx_quic_server_id_t));
+
+    } else {
+
+        sid = ngx_pcalloc(c->pool, sizeof(ngx_quic_server_id_t));
+        if (sid == NULL) {
+            return NULL;
+        }
+    }
+
+    return sid;
+}