Opened 2 years ago

Closed 2 years ago

#2308 closed defect (duplicate)

proxy_bind and proxy_pass address family mismatch causes connection fail

Reported by: lukaslihotzki@… Owned by:
Priority: minor Milestone:
Component: nginx-core Version:
Keywords: Cc:
uname -a: Linux lukas 5.16.1-arch1-1 #1 SMP PREEMPT Sun, 16 Jan 2022 11:39:23 +0000 x86_64 GNU/Linux
nginx -V: nginx version: nginx/1.20.2
built with OpenSSL 1.1.1l 24 Aug 2021 (running with OpenSSL 1.1.1m 14 Dec 2021)
TLS SNI support enabled
configure arguments: --prefix=/etc/nginx --conf-path=/etc/nginx/nginx.conf --sbin-path=/usr/bin/nginx --pid-path=/run/ --lock-path=/run/lock/nginx.lock --user=http --group=http --http-log-path=/var/log/nginx/access.log --error-log-path=stderr --http-client-body-temp-path=/var/lib/nginx/client-body --http-proxy-temp-path=/var/lib/nginx/proxy --http-fastcgi-temp-path=/var/lib/nginx/fastcgi --http-scgi-temp-path=/var/lib/nginx/scgi --http-uwsgi-temp-path=/var/lib/nginx/uwsgi --with-cc-opt='-march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions -Wp,-D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fstack-clash-protection -fcf-protection' --with-ld-opt=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now --with-compat --with-debug --with-file-aio --with-http_addition_module --with-http_auth_request_module --with-http_dav_module --with-http_degradation_module --with-http_flv_module --with-http_geoip_module --with-http_gunzip_module --with-http_gzip_static_module --with-http_mp4_module --with-http_realip_module --with-http_secure_link_module --with-http_slice_module --with-http_ssl_module --with-http_stub_status_module --with-http_sub_module --with-http_v2_module --with-mail --with-mail_ssl_module --with-pcre-jit --with-stream --with-stream_geoip_module --with-stream_realip_module --with-stream_ssl_module --with-stream_ssl_preread_module --with-threads


When using a hostname in proxy_pass, this hostname is effectively resolved to either an IPv4 or an IPv6 address. If proxy_bind contains a local address of the other family, an error like these occurs:

[crit]: *1 bind( failed (22: Invalid argument) while connecting to upstream
[crit]: *1 bind(::) failed (97: Address family not supported by protocol) while connecting to upstream

nginx already queries both the A and AAAA records, but for actual connection establishment, it needs to choose the record type matching to the proxy_bind address family.

If the proxy_bind address is IPv4 and hostnames are resolved dynamically, ipv6=off can be set in the resolver as a workaround, but there is no ipv4=off option for IPv6 proxy_bind addresses.

This bug can be reproduced in http and stream. A config file for reproducing this bug is attached.

Attachments (1)

nginx.conf (633 bytes ) - added by lukaslihotzki@… 2 years ago.

Download all attachments as: .zip

Change History (3)

by lukaslihotzki@…, 2 years ago

Attachment: nginx.conf added

comment:2 by Maxim Dounin, 2 years ago

Resolution: duplicate
Status: newclosed

As already found out by the reporter, duplicate of #1535.

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