I'm using nginx to proxy Icecast web server.

When I'm starting to stream data from the server, Nginx add a number between headers and real body. When I'm making the same request directly to Icecast this number isn't present.

Note: I'm using Kubernetes nginx ingress manager to generate config

My Nginx configuration:

daemon off;

worker_processes 2;
pid /run/nginx.pid;

worker_rlimit_nofile 100981;

worker_shutdown_timeout 10s ;

events {
    multi_accept on;
    worker_connections 16384;
    use epoll;
}

http {

    real_ip_header X-Forwarded-For;
    real_ip_recursive on;
    set_real_ip_from 0.0.0.0/0;

    aio threads;
    aio_write on;

    tcp_nopush on;
    tcp_nodelay on;

    log_subrequest on;

    reset_timedout_connection on;

    keepalive_timeout 75s;
    keepalive_requests 100;

    client_header_buffer_size 1k;
    client_header_timeout 60s;
    large_client_header_buffers 4 8k;
    client_body_buffer_size 8k;
    client_body_timeout 60s;

    types_hash_max_size 2048;
    server_names_hash_max_size 1024;
    server_names_hash_bucket_size 64;
    map_hash_bucket_size 64;

    proxy_headers_hash_max_size 512;
    proxy_headers_hash_bucket_size 64;

    variables_hash_bucket_size 128;
    variables_hash_max_size 2048;

    underscores_in_headers off;
    ignore_invalid_headers on;

    limit_req_status 503;

    include /etc/nginx/mime.types;
    default_type text/html;

    gzip on;
    gzip_comp_level 5;
    gzip_http_version 1.1;
    gzip_min_length 256;
    gzip_types application/atom+xml application/javascript application/x-javascript application/json application/rss+xml application/vnd.ms-fontobject application/x-font-ttf application/x-web-app-manifest+json application/xhtml+xml application/xml font/opentype image/svg+xml image/x-icon text/css text/plain text/x-component;
    gzip_proxied any;
    gzip_vary on;

    # Custom headers for response
    server_tokens on;

    # disable warnings
    uninitialized_variable_warn off;

    # Additional available variables:
    # $namespace
    # $ingress_name
    # $service_name
    log_format upstreaminfo '$the_real_ip - [$the_real_ip] - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" $request_length $request_time [$proxy_upstream_name] $upstream_addr $upstream_response_length $upstream_response_time $upstream_status';

    map $request_uri $loggable {
        default 1;
    }

    access_log /var/log/nginx/access.log upstreaminfo if=$loggable;

    error_log /var/log/nginx/error.log notice;

    resolver 10.6.30.8 valid=30s;

    # Retain the default nginx handling of requests without a "Connection" header
    map $http_upgrade $connection_upgrade {
        default upgrade;
        '' close;
    }

    map $http_x_forwarded_for $the_real_ip {
        default $remote_addr;
    }

    # trust http_x_forwarded_proto headers correctly indicate ssl offloading
    map $http_x_forwarded_proto $pass_access_scheme {
        default $http_x_forwarded_proto;
        '' $scheme;
    }

    # validate $pass_access_scheme and $scheme are http to force a redirect
    map "$scheme:$pass_access_scheme" $redirect_to_https {
        default 0;
        "http:http" 1;
        "https:http" 1;
    }

    map $http_x_forwarded_port $pass_server_port {
        default $http_x_forwarded_port;
        '' $server_port;
    }

    map $pass_server_port $pass_port {
        443 443;
        default $pass_server_port;
    }

    # Obtain best http host
    map $http_host $this_host {
        default $http_host;
        '' $host;
    }

    map $http_x_forwarded_host $best_http_host {
        default $http_x_forwarded_host;
        '' $this_host;
    }

    server_name_in_redirect off;
    port_in_redirect off;

    rewrite_log on;

    upstream upstream-default-backend {
        # Load balance algorithm; empty for round robin, which is the default
        least_conn;
        keepalive 32;
        server 10.244.5.2:8080 max_fails=0 fail_timeout=0;
    }

    upstream oma-clients-paj-icecast-icecast-client {
        # Load balance algorithm; empty for round robin, which is the default
        least_conn;
        keepalive 32;
        server 10.244.5.6:8000 max_fails=0 fail_timeout=0;
    }

    ## start server listen.oma-radio.fr
    server {
        server_name listen.oma-radio.fr ;

        listen 80;
        listen [::]:80;

        set $proxy_upstream_name "-";

        location /paj.ogg {
            port_in_redirect off;

            set $proxy_upstream_name "oma-clients-paj-icecast-icecast-client";

            client_max_body_size "2m";

            proxy_set_header Host $best_http_host;

            # Pass the extracted client certificate to the backend
            proxy_set_header ssl-client-cert "";
            proxy_set_header ssl-client-verify "";
            proxy_set_header ssl-client-dn "";

            # Allow websocket connections
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection $connection_upgrade;
            proxy_set_header X-Real-IP $the_real_ip;
            proxy_set_header X-Forwarded-For $the_real_ip;
            proxy_set_header X-Forwarded-Host $best_http_host;
            proxy_set_header X-Forwarded-Port $pass_port;
            proxy_set_header X-Forwarded-Proto $pass_access_scheme;
            proxy_set_header X-Original-URI $request_uri;
            proxy_set_header X-Scheme $pass_access_scheme;

            # Pass the original X-Forwarded-For
            proxy_set_header X-Original-Forwarded-For $http_x_forwarded_for;

            # mitigate HTTPoxy Vulnerability
            # https://www.nginx.com/blog/mitigating-the-httpoxy-vulnerability-with-nginx/
            proxy_set_header Proxy "";

            # Custom headers to proxied server
            proxy_connect_timeout 5s;
            proxy_send_timeout 60s;
            proxy_read_timeout 60s;

            proxy_buffering "off";
            proxy_buffer_size "4k";
            proxy_buffers 4 "4k";
            proxy_request_buffering "on";

            proxy_http_version 1.1;

            proxy_cookie_domain off;
            proxy_cookie_path off;

            # In case of errors try the next upstream server before returning an error
            proxy_next_upstream error timeout invalid_header http_502 http_503 http_504;

            proxy_pass http://oma-clients-paj-icecast-icecast-client;

            proxy_redirect off;
        }
    }
}

Here the TCP stream received with this configuration:

What is the cause of the presence of this number?
How to remove it from there?