server_name using regex loses variable after first request in h3

[Paul Scholz]

Nginx with h3 leaves variables generated by server_name regex empty.
I defined a variable called subdomain in the server_name to redirect based on it. While using it with h2 it works well. But when switching to h3 the regex variables are not set.

I tried this using

curl --http2 https://test.repo.limine.de/index.html

and

# alt-svc cache required
curl --http3 https://test.repo.limine.de/index.html

Proxied server shows empty subdomain variable using h3.

Setup is described below:

Config:

server {

    listen 443 http3;
    listen 443 ssl http2;

    # regex in server_name combined with h3 does not work well
    server_name ~^(?<subdomain>.*)\.repo\.limine\.de$;

    ssl_certificate         /etc/acme/limine.de/fullchain.pem;
    ssl_certificate_key     /etc/acme/limine.de/privkey.pem;
    ssl_trusted_certificate /etc/acme/limine.de/cert.pem;

    add_header alt-svc 'h3=":443"; ma=86400';
    add_header Strict-Transport-Security max-age=15768000;

    location ~ ^/(.*)$ {
        proxy_pass http://localhost:8080/$subdomain/$1;
    }

}

Serving HTTP on 0.0.0.0 port 8080 (http://0.0.0.0:8080/) ...
10.89.0.63 - - [08/Nov/2022 12:11:42] code 404, message File not found
10.89.0.63 - - [08/Nov/2022 12:11:42] "GET //index.html HTTP/1.0" 404 - h3
10.89.0.63 - - [08/Nov/2022 12:12:12] "GET /test/index.html HTTP/1.0" 200 - h2

[Sergey Kandaurov]

Can you please try this patch and report the results?

# HG changeset patch
# User Sergey Kandaurov <pluknet@nginx.com>
# Date 1668422301 -14400
#      Mon Nov 14 14:38:21 2022 +0400
# Branch quic
# Node ID e1c359fc6a4d7fbedfe31eb11057fdb8ab4981af
# Parent  3be9531610265d5e906baab1cac1cac608a952a3
HTTP/3: fixed server_name regex captures (ticket #2407).

Previously, HTTP/3 stream connection didn't inherit the servername regex
from the main QUIC connection saved when processing SNI and using regular
expressions in server names.  As a result, it didn't execute to set regex
captures when choosing the virtual server after parsing HTTP/3 headers.

diff --git a/src/http/v3/ngx_http_v3_request.c b/src/http/v3/ngx_http_v3_request.c
--- a/src/http/v3/ngx_http_v3_request.c
+++ b/src/http/v3/ngx_http_v3_request.c
@@ -83,6 +83,10 @@ ngx_http_v3_init(ngx_connection_t *c)
         hc->ssl_servername = phc->ssl_servername;
         hc->conf_ctx = phc->conf_ctx;
 
+        if (phc->ssl_servername_regex) {
+            hc->ssl_servername_regex = phc->ssl_servername_regex;
+        }
+
         ngx_set_connection_log(c, clcf->error_log);
     }
 

[Sergey Kandaurov]

A slightly modified patch committed in ​https://hg.nginx.org/nginx-quic/rev/0f5fc7a320db

[Sergey Kandaurov <pluknet@…>]

In 9037:0f5fc7a320db/nginx:

HTTP/3: fixed server_name regex captures (ticket #2407).

Previously, HTTP/3 stream connection didn't inherit the servername regex
from the main QUIC connection saved when processing SNI and using regular
expressions in server names. As a result, it didn't execute to set regex
captures when choosing the virtual server while parsing HTTP/3 headers.