QUIC: fixed migration during NAT rebinding. The RFC 9000 allows a packet from known CID arrive from unknown path: These requirements regarding connection ID reuse apply only to the sending of packets, as unintentional changes in path without a change in connection ID are possible. For example, after a period of network inactivity, NAT rebinding might cause packets to be sent on a new path when the client resumes sending. Before the patch, such packets were rejected with an error in the ngx_quic_check_migration() function. Removing the check makes the separate function excessive - remaining checks are early migration check and "disable_active_migration" check. The latter is a transport parameter sent to client and it should not be used by server. The server should send "disable_active_migration" "if the endpoint does not support active connection migration" (18.2). The support status depends on nginx configuration: to have migration working with multiple workers, you need bpf helper, available on recent Linux systems. The patch does not set "disable_active_migration" automatically and leaves it for the administrator. By default, active migration is enabled. RFC 900 says that it is ok to migrate if the peer violates "disable_active_migration" flag requirements: If the peer violates this requirement, the endpoint MUST either drop the incoming packets on that path without generating a Stateless Reset OR proceed with path validation and allow the peer to migrate. Generating a Stateless Reset or closing the connection would allow third parties in the network to cause connections to close by spoofing or otherwise manipulating observed traffic. So, nginx adheres to the second option and proceeds to path validation. Note: The ngtcp2 may be used for testing both active migration and NAT rebinding: ngtcp2/client --change-local-addr=200ms --delay-stream=500ms <ip> <port> <url> ngtcp2/client --change-local-addr=200ms --delay-stream=500ms --nat-rebinding \ <ip> <port> <url>

/*
 * Copyright (C) Nginx, Inc.
 */


#ifndef _NGX_EVENT_QUIC_OUTPUT_H_INCLUDED_
#define _NGX_EVENT_QUIC_OUTPUT_H_INCLUDED_


#include <ngx_config.h>
#include <ngx_core.h>


size_t ngx_quic_max_udp_payload(ngx_connection_t *c);

ngx_int_t ngx_quic_output(ngx_connection_t *c);

ngx_int_t ngx_quic_negotiate_version(ngx_connection_t *c,
    ngx_quic_header_t *inpkt);

int ngx_quic_send_alert(ngx_ssl_conn_t *ssl_conn,
    enum ssl_encryption_level_t level, uint8_t alert);

ngx_int_t ngx_quic_send_stateless_reset(ngx_connection_t *c,
    ngx_quic_conf_t *conf, ngx_quic_header_t *pkt);
ngx_int_t ngx_quic_send_cc(ngx_connection_t *c);
ngx_int_t ngx_quic_send_early_cc(ngx_connection_t *c,
    ngx_quic_header_t *inpkt, ngx_uint_t err, const char *reason);

ngx_int_t ngx_quic_send_retry(ngx_connection_t *c,
    ngx_quic_conf_t *conf, ngx_quic_header_t *pkt);
ngx_int_t ngx_quic_send_new_token(ngx_connection_t *c, ngx_quic_path_t *path);

ngx_int_t ngx_quic_send_ack(ngx_connection_t *c,
    ngx_quic_send_ctx_t *ctx);
ngx_int_t ngx_quic_send_ack_range(ngx_connection_t *c,
    ngx_quic_send_ctx_t *ctx, uint64_t smallest, uint64_t largest);

ssize_t ngx_quic_frame_sendto(ngx_connection_t *c, ngx_quic_frame_t *frame,
    size_t min, struct sockaddr *sockaddr, socklen_t socklen);

#endif /* _NGX_EVENT_QUIC_OUTPUT_H_INCLUDED_ */