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src/event/quic/ngx_event_quic_migration.c

@@ -0,0 +1,671 @@
+
+/*
+ * Copyright (C) Nginx, Inc.
+ */
+
+
+#include <ngx_config.h>
+#include <ngx_core.h>
+#include <ngx_event.h>
+#include <ngx_event_quic_connection.h>
+
+
+static void ngx_quic_set_connection_path(ngx_connection_t *c,
+    ngx_quic_path_t *path);
+static ngx_int_t ngx_quic_validate_path(ngx_connection_t *c,
+    ngx_quic_path_t *path);
+static ngx_int_t ngx_quic_send_path_challenge(ngx_connection_t *c,
+    ngx_quic_path_t *path);
+static ngx_quic_path_t *ngx_quic_get_path(ngx_connection_t *c, ngx_uint_t tag);
+
+
+ngx_int_t
+ngx_quic_handle_path_challenge_frame(ngx_connection_t *c,
+    ngx_quic_header_t *pkt, ngx_quic_path_challenge_frame_t *f)
+{
+    ngx_quic_frame_t        frame, *fp;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    ngx_memzero(&frame, sizeof(ngx_quic_frame_t));
+
+    frame.level = ssl_encryption_application;
+    frame.type = NGX_QUIC_FT_PATH_RESPONSE;
+    frame.u.path_response = *f;
+
+    /*
+     * RFC 9000, 8.2.2.  Path Validation Responses
+     *
+     * A PATH_RESPONSE frame MUST be sent on the network path where the
+     * PATH_CHALLENGE frame was received.
+     */
+
+    /*
+     * An endpoint MUST expand datagrams that contain a PATH_RESPONSE frame
+     * to at least the smallest allowed maximum datagram size of 1200 bytes.
+     */
+    if (ngx_quic_frame_sendto(c, &frame, 1200, pkt->path) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    if (pkt->path == qc->path) {
+        /*
+         * RFC 9000, 9.3.3.  Off-Path Packet Forwarding
+         *
+         * An endpoint that receives a PATH_CHALLENGE on an active path SHOULD
+         * send a non-probing packet in response.
+         */
+
+        fp = ngx_quic_alloc_frame(c);
+        if (fp == NULL) {
+            return NGX_ERROR;
+        }
+
+        fp->level = ssl_encryption_application;
+        fp->type = NGX_QUIC_FT_PING;
+
+        ngx_quic_queue_frame(qc, fp);
+    }
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
+ngx_quic_handle_path_response_frame(ngx_connection_t *c,
+    ngx_quic_path_challenge_frame_t *f)
+{
+    ngx_uint_t              rst;
+    ngx_queue_t            *q;
+    ngx_quic_path_t        *path, *prev;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    /*
+     * RFC 9000, 8.2.3.  Successful Path Validation
+     *
+     * A PATH_RESPONSE frame received on any network path validates the path
+     * on which the PATH_CHALLENGE was sent.
+     */
+
+    for (q = ngx_queue_head(&qc->paths);
+         q != ngx_queue_sentinel(&qc->paths);
+         q = ngx_queue_next(q))
+    {
+        path = ngx_queue_data(q, ngx_quic_path_t, queue);
+
+        if (!path->validating) {
+            continue;
+        }
+
+        if (ngx_memcmp(path->challenge1, f->data, sizeof(f->data)) == 0
+            || ngx_memcmp(path->challenge2, f->data, sizeof(f->data)) == 0)
+        {
+            goto valid;
+        }
+    }
+
+    ngx_log_debug0(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic stale PATH_RESPONSE ignored");
+
+    return NGX_OK;
+
+valid:
+
+    /*
+     * RFC 9000, 9.4.  Loss Detection and Congestion Control
+     *
+     * On confirming a peer's ownership of its new address,
+     * an endpoint MUST immediately reset the congestion controller
+     * and round-trip time estimator for the new path to initial values
+     * unless the only change in the peer's address is its port number.
+     */
+
+    rst = 1;
+
+    prev = ngx_quic_get_path(c, NGX_QUIC_PATH_BACKUP);
+
+    if (prev != NULL) {
+
+        if (ngx_cmp_sockaddr(prev->sockaddr, prev->socklen,
+                             path->sockaddr, path->socklen, 0)
+            == NGX_OK)
+        {
+            /* address did not change */
+            rst = 0;
+        }
+    }
+
+    if (rst) {
+        ngx_memzero(&qc->congestion, sizeof(ngx_quic_congestion_t));
+
+        qc->congestion.window = ngx_min(10 * qc->tp.max_udp_payload_size,
+                                   ngx_max(2 * qc->tp.max_udp_payload_size,
+                                           14720));
+        qc->congestion.ssthresh = (size_t) -1;
+        qc->congestion.recovery_start = ngx_current_msec;
+    }
+
+    /*
+     * RFC 9000, 9.3.  Responding to Connection Migration
+     *
+     *  After verifying a new client address, the server SHOULD
+     *  send new address validation tokens (Section 8) to the client.
+     */
+
+    if (ngx_quic_send_new_token(c, path) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    ngx_log_error(NGX_LOG_INFO, c->log, 0,
+                  "quic path seq:%uL addr:%V successfully validated",
+                  path->seqnum, &path->addr_text);
+
+    ngx_quic_path_dbg(c, "is validated", path);
+
+    path->validated = 1;
+    path->validating = 0;
+    path->limited = 0;
+
+    return NGX_OK;
+}
+
+
+ngx_quic_path_t *
+ngx_quic_new_path(ngx_connection_t *c,
+    struct sockaddr *sockaddr, socklen_t socklen, ngx_quic_client_id_t *cid)
+{
+    ngx_queue_t            *q;
+    ngx_quic_path_t        *path;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    if (!ngx_queue_empty(&qc->free_paths)) {
+
+        q = ngx_queue_head(&qc->free_paths);
+        path = ngx_queue_data(q, ngx_quic_path_t, queue);
+
+        ngx_queue_remove(&path->queue);
+
+        ngx_memzero(path, sizeof(ngx_quic_path_t));
+
+    } else {
+
+        path = ngx_pcalloc(c->pool, sizeof(ngx_quic_path_t));
+        if (path == NULL) {
+            return NULL;
+        }
+    }
+
+    ngx_queue_insert_tail(&qc->paths, &path->queue);
+
+    path->cid = cid;
+    cid->used = 1;
+
+    path->limited = 1;
+
+    path->seqnum = qc->path_seqnum++;
+
+    path->sockaddr = &path->sa.sockaddr;
+    path->socklen = socklen;
+    ngx_memcpy(path->sockaddr, sockaddr, socklen);
+
+    path->addr_text.data = path->text;
+    path->addr_text.len = ngx_sock_ntop(sockaddr, socklen, path->text,
+                                        NGX_SOCKADDR_STRLEN, 1);
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic path seq:%uL created addr:%V",
+                   path->seqnum, &path->addr_text);
+    return path;
+}
+
+
+static ngx_quic_path_t *
+ngx_quic_get_path(ngx_connection_t *c, ngx_uint_t tag)
+{
+    ngx_queue_t            *q;
+    ngx_quic_path_t        *path;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    for (q = ngx_queue_head(&qc->paths);
+         q != ngx_queue_sentinel(&qc->paths);
+         q = ngx_queue_next(q))
+    {
+        path = ngx_queue_data(q, ngx_quic_path_t, queue);
+
+        if (path->tag == tag) {
+            return path;
+        }
+    }
+
+    return NULL;
+}
+
+
+ngx_int_t
+ngx_quic_set_path(ngx_connection_t *c, ngx_quic_header_t *pkt)
+{
+    off_t                   len;
+    ngx_queue_t            *q;
+    ngx_quic_path_t        *path, *probe;
+    ngx_quic_socket_t      *qsock;
+    ngx_quic_send_ctx_t    *ctx;
+    ngx_quic_client_id_t   *cid;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+    qsock = ngx_quic_get_socket(c);
+
+    len = pkt->raw->last - pkt->raw->start;
+
+    if (c->udp->buffer == NULL) {
+        /* first ever packet in connection, path already exists  */
+        path = qc->path;
+        goto update;
+    }
+
+    probe = NULL;
+
+    for (q = ngx_queue_head(&qc->paths);
+         q != ngx_queue_sentinel(&qc->paths);
+         q = ngx_queue_next(q))
+    {
+        path = ngx_queue_data(q, ngx_quic_path_t, queue);
+
+        if (ngx_cmp_sockaddr(&qsock->sockaddr.sockaddr, qsock->socklen,
+                             path->sockaddr, path->socklen, 1)
+            == NGX_OK)
+        {
+            goto update;
+        }
+
+        if (path->tag == NGX_QUIC_PATH_PROBE) {
+            probe = path;
+        }
+    }
+
+    /* packet from new path, drop current probe, if any */
+
+    ctx = ngx_quic_get_send_ctx(qc, pkt->level);
+
+    /*
+     * only accept highest-numbered packets to prevent connection id
+     * exhaustion by excessive probing packets from unknown paths
+     */
+    if (pkt->pn != ctx->largest_pn) {
+        return NGX_DONE;
+    }
+
+    if (probe && ngx_quic_free_path(c, probe) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    /* new path requires new client id */
+    cid = ngx_quic_next_client_id(c);
+    if (cid == NULL) {
+        ngx_log_error(NGX_LOG_INFO, c->log, 0,
+                      "quic no available client ids for new path");
+        /* stop processing of this datagram */
+        return NGX_DONE;
+    }
+
+    path = ngx_quic_new_path(c, &qsock->sockaddr.sockaddr, qsock->socklen, cid);
+    if (path == NULL) {
+        return NGX_ERROR;
+    }
+
+    path->tag = NGX_QUIC_PATH_PROBE;
+
+    /*
+     * client arrived using new path and previously seen DCID,
+     * this indicates NAT rebinding (or bad client)
+     */
+    if (qsock->used) {
+        pkt->rebound = 1;
+    }
+
+update:
+
+    qsock->used = 1;
+    pkt->path = path;
+
+    /* TODO: this may be too late in some cases;
+     *       for example, if error happens during decrypt(), we cannot
+     *       send CC, if error happens in 1st packet, due to amplification
+     *       limit, because path->received = 0
+     *
+     *       should we account garbage as received or only decrypting packets?
+     */
+    path->received += len;
+
+    ngx_log_debug3(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic packet len:%O via sock seq:%L path seq:%uL",
+                   len, (int64_t) qsock->sid.seqnum, path->seqnum);
+    ngx_quic_path_dbg(c, "status", path);
+
+    return NGX_OK;
+}
+
+
+ngx_int_t
+ngx_quic_free_path(ngx_connection_t *c, ngx_quic_path_t *path)
+{
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    ngx_queue_remove(&path->queue);
+    ngx_queue_insert_head(&qc->free_paths, &path->queue);
+
+    /*
+     * invalidate CID that is no longer usable for any other path;
+     * this also requests new CIDs from client
+     */
+    if (path->cid) {
+        if (ngx_quic_free_client_id(c, path->cid) != NGX_OK) {
+            return NGX_ERROR;
+        }
+    }
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic path seq:%uL addr:%V retired",
+                   path->seqnum, &path->addr_text);
+
+    return NGX_OK;
+}
+
+
+static void
+ngx_quic_set_connection_path(ngx_connection_t *c, ngx_quic_path_t *path)
+{
+    size_t  len;
+
+    ngx_memcpy(c->sockaddr, path->sockaddr, path->socklen);
+    c->socklen = path->socklen;
+
+    if (c->addr_text.data) {
+        len = ngx_min(c->addr_text.len, path->addr_text.len);
+
+        ngx_memcpy(c->addr_text.data, path->addr_text.data, len);
+        c->addr_text.len = len;
+    }
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic send path set to seq:%uL addr:%V",
+                   path->seqnum, &path->addr_text);
+}
+
+
+ngx_int_t
+ngx_quic_handle_migration(ngx_connection_t *c, ngx_quic_header_t *pkt)
+{
+    ngx_quic_path_t        *next, *bkp;
+    ngx_quic_send_ctx_t    *ctx;
+    ngx_quic_connection_t  *qc;
+
+    /* got non-probing packet via non-active path */
+
+    qc = ngx_quic_get_connection(c);
+
+    ctx = ngx_quic_get_send_ctx(qc, pkt->level);
+
+    /*
+     * RFC 9000, 9.3.  Responding to Connection Migration
+     *
+     * An endpoint only changes the address to which it sends packets in
+     * response to the highest-numbered non-probing packet.
+     */
+    if (pkt->pn != ctx->largest_pn) {
+        return NGX_OK;
+    }
+
+    next = pkt->path;
+
+    /*
+     * RFC 9000, 9.3.3:
+     *
+     * In response to an apparent migration, endpoints MUST validate the
+     * previously active path using a PATH_CHALLENGE frame.
+     */
+    if (pkt->rebound) {
+
+        /* NAT rebinding: client uses new path with old SID */
+        if (ngx_quic_validate_path(c, qc->path) != NGX_OK) {
+            return NGX_ERROR;
+        }
+    }
+
+    if (qc->path->validated) {
+
+        if (next->tag != NGX_QUIC_PATH_BACKUP) {
+            /* can delete backup path, if any */
+            bkp = ngx_quic_get_path(c, NGX_QUIC_PATH_BACKUP);
+
+            if (bkp && ngx_quic_free_path(c, bkp) != NGX_OK) {
+                return NGX_ERROR;
+            }
+        }
+
+        qc->path->tag = NGX_QUIC_PATH_BACKUP;
+        ngx_quic_path_dbg(c, "is now backup", qc->path);
+
+    } else {
+        if (ngx_quic_free_path(c, qc->path) != NGX_OK) {
+            return NGX_ERROR;
+        }
+    }
+
+    /* switch active path to migrated */
+    qc->path = next;
+    qc->path->tag = NGX_QUIC_PATH_ACTIVE;
+
+    ngx_quic_set_connection_path(c, next);
+
+    if (!next->validated && !next->validating) {
+        if (ngx_quic_validate_path(c, next) != NGX_OK) {
+            return NGX_ERROR;
+        }
+    }
+
+    ngx_log_error(NGX_LOG_INFO, c->log, 0,
+                  "quic migrated to path seq:%uL addr:%V",
+                  qc->path->seqnum, &qc->path->addr_text);
+
+    ngx_quic_path_dbg(c, "is now active", qc->path);
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_quic_validate_path(ngx_connection_t *c, ngx_quic_path_t *path)
+{
+    ngx_msec_t              pto;
+    ngx_quic_send_ctx_t    *ctx;
+    ngx_quic_connection_t  *qc;
+
+    qc = ngx_quic_get_connection(c);
+
+    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic initiated validation of path seq:%uL", path->seqnum);
+
+    path->validating = 1;
+
+    if (RAND_bytes(path->challenge1, 8) != 1) {
+        return NGX_ERROR;
+    }
+
+    if (RAND_bytes(path->challenge2, 8) != 1) {
+        return NGX_ERROR;
+    }
+
+    if (ngx_quic_send_path_challenge(c, path) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    ctx = ngx_quic_get_send_ctx(qc, ssl_encryption_application);
+    pto = ngx_quic_pto(c, ctx);
+
+    path->expires = ngx_current_msec + pto;
+    path->tries = NGX_QUIC_PATH_RETRIES;
+
+    if (!qc->path_validation.timer_set) {
+        ngx_add_timer(&qc->path_validation, pto);
+    }
+
+    return NGX_OK;
+}
+
+
+static ngx_int_t
+ngx_quic_send_path_challenge(ngx_connection_t *c, ngx_quic_path_t *path)
+{
+    ngx_quic_frame_t  frame;
+
+    ngx_log_debug2(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic path seq:%uL send path_challenge tries:%ui",
+                   path->seqnum, path->tries);
+
+    ngx_memzero(&frame, sizeof(ngx_quic_frame_t));
+
+    frame.level = ssl_encryption_application;
+    frame.type = NGX_QUIC_FT_PATH_CHALLENGE;
+
+    ngx_memcpy(frame.u.path_challenge.data, path->challenge1, 8);
+
+    /*
+     * RFC 9000, 8.2.1.  Initiating Path Validation
+     *
+     * An endpoint MUST expand datagrams that contain a PATH_CHALLENGE frame
+     * to at least the smallest allowed maximum datagram size of 1200 bytes,
+     * unless the anti-amplification limit for the path does not permit
+     * sending a datagram of this size.
+     */
+
+     /* same applies to PATH_RESPONSE frames */
+    if (ngx_quic_frame_sendto(c, &frame, 1200, path) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    ngx_memcpy(frame.u.path_challenge.data, path->challenge2, 8);
+
+    if (ngx_quic_frame_sendto(c, &frame, 1200, path) != NGX_OK) {
+        return NGX_ERROR;
+    }
+
+    return NGX_OK;
+}
+
+
+void
+ngx_quic_path_validation_handler(ngx_event_t *ev)
+{
+    ngx_msec_t              now;
+    ngx_queue_t            *q;
+    ngx_msec_int_t          left, next, pto;
+    ngx_quic_path_t        *path, *bkp;
+    ngx_connection_t       *c;
+    ngx_quic_send_ctx_t    *ctx;
+    ngx_quic_connection_t  *qc;
+
+    c = ev->data;
+    qc = ngx_quic_get_connection(c);
+
+    ctx = ngx_quic_get_send_ctx(qc, ssl_encryption_application);
+    pto = ngx_quic_pto(c, ctx);
+
+    next = -1;
+    now = ngx_current_msec;
+
+    q = ngx_queue_head(&qc->paths);
+
+    while (q != ngx_queue_sentinel(&qc->paths)) {
+
+        path = ngx_queue_data(q, ngx_quic_path_t, queue);
+        q = ngx_queue_next(q);
+
+        if (!path->validating) {
+            continue;
+        }
+
+        left = path->expires - now;
+
+        if (left > 0) {
+
+            if (next == -1 || left < next) {
+                next = left;
+            }
+
+            continue;
+        }
+
+        if (--path->tries) {
+            path->expires = ngx_current_msec + pto;
+
+            if (next == -1 || pto < next) {
+                next = pto;
+            }
+
+            /* retransmit */
+            (void) ngx_quic_send_path_challenge(c, path);
+
+            continue;
+        }
+
+        ngx_log_debug1(NGX_LOG_DEBUG_EVENT, ev->log, 0,
+                       "quic path seq:%uL validation failed", path->seqnum);
+
+        /* found expired path */
+
+        path->validated = 0;
+        path->validating = 0;
+        path->limited = 1;
+
+
+        /* RFC 9000, 9.3.2.  On-Path Address Spoofing
+         *
+         * To protect the connection from failing due to such a spurious
+         * migration, an endpoint MUST revert to using the last validated
+         * peer address when validation of a new peer address fails.
+         */
+
+        if (qc->path == path) {
+            /* active path validation failed */
+
+            bkp = ngx_quic_get_path(c, NGX_QUIC_PATH_BACKUP);
+
+            if (bkp == NULL) {
+                qc->error = NGX_QUIC_ERR_NO_VIABLE_PATH;
+                qc->error_reason = "no viable path";
+                ngx_quic_close_connection(c, NGX_ERROR);
+                return;
+            }
+
+            qc->path = bkp;
+            qc->path->tag = NGX_QUIC_PATH_ACTIVE;
+
+            ngx_quic_set_connection_path(c, qc->path);
+
+            ngx_log_error(NGX_LOG_INFO, c->log, 0,
+                          "quic path seq:%uL addr:%V is restored from backup",
+                          qc->path->seqnum, &qc->path->addr_text);
+
+            ngx_quic_path_dbg(c, "is active", qc->path);
+        }
+
+        if (ngx_quic_free_path(c, path) != NGX_OK) {
+            ngx_quic_close_connection(c, NGX_ERROR);
+            return;
+        }
+    }
+
+    if (next != -1) {
+        ngx_add_timer(&qc->path_validation, next);
+    }
+}