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(https://stackoverflow.co/labs/)   Learn more about Labs   (https://cdn.sstatic.net/Sites/stackoverflow/Img/apple-touch-icon.png?v=c78bd457575a) (/questions/52277929/nginx-408-timeout-reading-client-request-headers) NGINX 408 timeout (reading client request headers)  (/questions/ask) Ask Question     (2018-09-11 14:12:01Z) Asked 6 years, 5 months ago  Modified (?lastactivity) (2024-07-15 06:01:40Z) 7 months ago  (Viewed 17,082 times) Viewed 17k times         This question shows research effort; it is useful and clear  (70:3:31e,16:dbb636fbbca2db6a,10:1740036919,16:343b2a0140acd777,8:52277929,dde427fdc90599ee05e325474b61f6a113cb094c951d7ecba8986d348b489a66) 4  (This question does not show any research effort; it is unclear or not useful)    (70:3:31e,16:3f2cc5d8c8ae1607,10:1740036919,16:e0500d3d59922ca2,8:52277929,1630b5602292ae6f1075dc5ba15707c1d33ceba40304c09490a4a0329272552d)      Save this question.  (/posts/52277929/timeline)    Show activity on this post.    I'm working on a server that is receiving requests from IoT devices. They perform a HEAD request on boot. Unfortunately, it seems there's something wrong with the headers. NGINX access log [11/Sep/2018:13:41:11 +0000] "HEAD / HTTP/1.1" 408 0 "-" "-" --- "-" "-"   The log format is as follows log_format custom '[$time_local] "$request" $status $body_bytes_sent '
                  '"$http_referer" "$http_user_agent" ---'
                  '"$content_type" "$content_length"';   NGINX error log 2018/09/11 13:40:11 [debug] 31368#31368: *1 accept: SRCIP:33930 fd:32
2018/09/11 13:40:11 [debug] 31368#31368: *1 event timer add: 32: 60000:1536673271229
2018/09/11 13:40:11 [debug] 31368#31368: *1 reusable connection: 1
2018/09/11 13:40:11 [debug] 31368#31368: *1 epoll add event: fd:32 op:1 ev:80002001
2018/09/11 13:40:11 [debug] 31368#31368: *1 post event 000056011DBAA2C0
2018/09/11 13:40:11 [debug] 31368#31368: *1 delete posted event 000056011DBAA2C0
2018/09/11 13:40:11 [debug] 31368#31368: *1 http wait request handler
2018/09/11 13:40:11 [debug] 31368#31368: *1 malloc: 000056011DAAB650:1024
2018/09/11 13:40:11 [debug] 31368#31368: *1 recv: fd:32 71 of 1024
2018/09/11 13:40:11 [debug] 31368#31368: *1 reusable connection: 0
2018/09/11 13:40:11 [debug] 31368#31368: *1 posix_memalign: 000056011DB0DCD0:4096 @16
2018/09/11 13:40:11 [debug] 31368#31368: *1 http process request line
2018/09/11 13:40:11 [debug] 31368#31368: *1 http request line: "HEAD / HTTP/1.1"
2018/09/11 13:40:11 [debug] 31368#31368: *1 http uri: "/"
2018/09/11 13:40:11 [debug] 31368#31368: *1 http args: ""
2018/09/11 13:40:11 [debug] 31368#31368: *1 http exten: ""
2018/09/11 13:40:11 [debug] 31368#31368: *1 posix_memalign: 000056011DB690C0:4096 @16
2018/09/11 13:40:11 [debug] 31368#31368: *1 http process request header line
2018/09/11 13:40:11 [debug] 31368#31368: *1 http header: "Host: MYHOST"
2018/09/11 13:40:11 [debug] 31368#31368: *1 recv: fd:32 -1 of 953
2018/09/11 13:40:11 [debug] 31368#31368: *1 recv() not ready (11: Resource temporarily unavailable)
2018/09/11 13:41:11 [debug] 31368#31368: *1 event timer del: 32: 1536673271229
2018/09/11 13:41:11 [debug] 31368#31368: *1 http process request header line
2018/09/11 13:41:11 [info] 31368#31368: *1 client timed out (110: Connection timed out) while reading client request headers, client: SRCIP, server: MYHOST, request: "HEAD / HTTP/1.1", host: "MYHOST"
2018/09/11 13:41:11 [debug] 31368#31368: *1 http request count:1 blk:0
2018/09/11 13:41:11 [debug] 31368#31368: *1 http close request
2018/09/11 13:41:11 [debug] 31368#31368: *1 http log handler
2018/09/11 13:41:11 [debug] 31368#31368: *1 free: 000056011DB0DCD0, unused: 707
2018/09/11 13:41:11 [debug] 31368#31368: *1 free: 000056011DB690C0, unused: 3104
2018/09/11 13:41:11 [debug] 31368#31368: *1 close http connection: 32
2018/09/11 13:41:11 [debug] 31368#31368: *1 reusable connection: 0
2018/09/11 13:41:11 [debug] 31368#31368: *1 free: 000056011DAAB650
2018/09/11 13:41:11 [debug] 31368#31368: *1 free: 000056011DAFF960, unused: 128   Tcpdump sudo tcpdump -n -S -s 0 -A 'src SRCIP and port 80' shows 13:55:32.846408 IP SRCIP.39761 > DSTIP.80: Flags [S], seq 1846787, win 2920, options [mss 1460], length 0
E..,....p. *E......h.Q.P........`..h\;........
13:55:33.153456 IP SRCIP.39761 > DSTIP.80: Flags [.], ack 3538300854, win 2920, length 0
E..(....p..^E......h.Q.P....../.P..hqK........
13:55:33.314206 IP SRCIP.39761 > DSTIP.80: Flags [P.], seq 1846788:1846859, ack 3538300854, win 2920, length 71: HTTP: HEAD / HTTP/1.1
E..o&...p..CE......h.Q.P....../.P..hg...HEAD / HTTP/1.1
Host: MYHOST
Content-Length:
13:56:33.363048 IP SRCIP.39761 > DSTIP.80: Flags [F.], seq 1846859, ack 3538300855, win 2919, length 0
E..(....p...E......h.Q.P...K../.P..gq.........   I cannot change the firmware in the devices so I'm looking for a workaround on the NGINX side. Please let me know if I can provide more info to help with the answer. EDIT: I'm not adding the server config because I've tried too many and I'm not sure what to paste here. EDIT 2: tcpdump at first logs  13:55:32.846408 IP SRCIP.39761 > DSTIP.80: Flags [S], seq 1846787, win 2920, options [mss 1460], length 0
E..,....p. *E......h.Q.P........`..h\;........
13:55:33.153456 IP SRCIP.39761 > DSTIP.80: Flags [.], ack 3538300854, win 2920, length 0
E..(....p..^E......h.Q.P....../.P..hqK........
13:55:33.314206 IP SRCIP.39761 > DSTIP.80: Flags [P.], seq 1846788:1846859, ack 3538300854, win 2920, length 71: HTTP: HEAD / HTTP/1.1
E..o&...p..CE......h.Q.P....../.P..hg...HEAD / HTTP/1.1
Host: MYHOST
Content-Length:   And then the rest after some time. I assume it's after NGINX times out. EDIT 3: I finally understand what's going on. This has been really confusing because there's one Apache server in production with which the devices work properly. While trying to switch to NGINX things stopped working. As I've said above, the IoT devices on boot are performing a HEAD request. They expect a response with a Date: header so that they can parse it. Currently, the device are working fine with Apache because when a timeout is triggered while waiting for headers from the client, Apache returns a 408 response to the client, including the Date: header. This directive can set various timeouts for receiving the request headers and the request body from the client. If the client fails to send headers or body within the configured time, a 408 REQUEST TIME OUT error is sent.
  ((https://httpd.apache.org/docs/2.4/mod/mod_reqtimeout.html) https://httpd.apache.org/docs/2.4/mod/mod_reqtimeout.html )  On the other hand, NGINX when a when a timeout is triggered while waiting for headers from the client, just closes the connection without returning anything to the client. Even if it logs 408 in the access log. Defines a timeout for reading client request header. If a client does not transmit the entire header within this time, the request is terminated with the 408 (Request Time-out) error.
  ((http://nginx.org/en/docs/http/ngx_http_core_module.html#client_header_timeout) http://nginx.org/en/docs/http/ngx_http_core_module.html#client_header_timeout )  There's been a discussion on this behaviour already (https://trac.nginx.org/nginx/ticket/1005) https://trac.nginx.org/nginx/ticket/1005 . In other words, the HEAD request from the IoT devices has always being wrong. It just works with Apache because a 408 response with Date: is sent back whenever a timeout while waiting for headers is triggered. As I said above, unfortunately there's no way for me to change how the devices work. Thus, I need to workaround in NGINX. The only way I found is to change the source and compile myself. This is what I came up with by copy / pasting from the internet. Unfortunately, I haven't had time to understand the code and prolly won't ever. It would be really great if somebody helped me understanding how bad that code is and what's a better way of writing it.  The version of NGINX is 1.14.0. diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
index 2db7a62..086701b 100644
--- a/src/http/ngx_http_request.c
+++ b/src/http/ngx_http_request.c
@@ -1236,7 +1236,7 @@ ngx_http_process_request_headers(ngx_event_t *rev)
     if (rev->timedout) {
         ngx_log_error(NGX_LOG_INFO, c->log, NGX_ETIMEDOUT, "client timed out");
         c->timedout = 1;
-        ngx_http_close_request(r, NGX_HTTP_REQUEST_TIME_OUT);
+        ngx_http_finalize_request(r, ngx_http_special_response_handler(r, NGX_HTTP_REQUEST_TIME_OUT));
         return;
     }   To validate the code is working I used Telnet: This is what NGINX normally would do Request $ telnet HOST 80
Trying IP...
Connected to HOST.
Escape character is '^]'.
HEAD / HTTP/1.1
Content-Length:   Response Connection closed by foreign host.   This is what NGINX does with the modified code Request $ telnet HOST 80
Trying IP...
Connected to HOST.
Escape character is '^]'.
HEAD / HTTP/1.1
Content-Length:   Response HTTP/1.1 408 Request Time-out
Server: nginx
Date: Tue, 25 Sep 2018 08:18:41 GMT
Content-Type: text/html
Content-Length: 176
Connection: close   Notice that I could use another header in place of Content-Length: (e.g. Accept: and the result would be the same). If you are trying to reproduce just remember to press enter once (and only once) after the empty header (in the example Content-Length: ).  (/questions/tagged/nginx) (show questions tagged 'nginx') nginx      (/q/52277929) (Short permalink to this question) Share  Share a link to this question     Copy link (https://creativecommons.org/licenses/by-sa/4.0/) (The current license for this post: CC BY-SA 4.0) CC BY-SA 4.0     (/posts/52277929/edit) () Improve this question  Follow (70:3:31e,16:f6c43105cee0572c,10:1740036919,16:8bc864dc21f87725,8:52277929,bb7eb629eed192894413778973c87f7a1e4f12a11c00e83dd025e900c56fe9e5)  Follow this question to receive notifications       (/posts/52277929/revisions) (show all edits to this post) edited (2018-09-25 08:27:59Z) Sep 25, 2018 at 8:27     3v0k4     asked (2018-09-11 14:12:01Z) Sep 11, 2018 at 14:12   (/users/2700809/3v0k4) (3v0k4's user avatar)    (/users/2700809/3v0k4) 3v0k4 3v0k4 (reputation score) 161 (1 gold badge)  1  1 gold badge (4 silver badges)  4  4 silver badges (10 bronze badges)  10  10 bronze badges        6   It looks like they never send value for the Content-Length header, and they don't send the "blank line " after the headers either... How is the server supposed to know that the client has finished sending the headers? – (/users/1347519/attie) (6,979 reputation) Attie  Commented (2018-09-11 14:26:45Z, License: CC BY-SA 4.0) Sep 11, 2018 at 14:26        Do you have control of the Content-Length value or the content? If so, is it expected to include a newline, but is currently empty? – (/users/1347519/attie) (6,979 reputation) Attie  Commented (2018-09-11 14:27:31Z, License: CC BY-SA 4.0) Sep 11, 2018 at 14:27        What are the devices? – (/users/1347519/attie) (6,979 reputation) Attie  Commented (2018-09-11 14:27:40Z, License: CC BY-SA 4.0) Sep 11, 2018 at 14:27        Sensors with a custom firmware. Unfortunately, there's no way for me to change the code in the sensors. I need to find a workaround in NGINX. – (/users/2700809/3v0k4) (161 reputation) 3v0k4  Commented (2018-09-11 14:35:36Z, License: CC BY-SA 4.0) Sep 11, 2018 at 14:35        I'm not totally sure what's going on. One thing I forgot to mention is that tcpdump stops at Content-Length: for some time. I assume it's because NGINX is waiting for data but the sensor does not send anything. – (/users/2700809/3v0k4) (161 reputation) 3v0k4  Commented (2018-09-11 14:38:11Z, License: CC BY-SA 4.0) Sep 11, 2018 at 14:38        (Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.)  |  (Expand to show all comments on this post) Show 1 more comment         2 Answers 2   Sorted by:  (/questions/52277929/nginx-408-timeout-reading-client-request-headers?answertab=scoredesc#tab-top) Reset to default   (scoredesc) Highest score (default)  (trending) Trending (recent votes count more)  (modifieddesc) Date modified (newest first)  (createdasc) Date created (oldest first)            This answer is useful  (70:3:31e,16:c25afbaf0b985922,10:1740036919,16:66a9f3076e4a05c1,8:52566534,634beeaa942404a5062338b67d90d6c01c6dc98c4cea6da7808cf0d147283d11) -1  (This answer is not useful)    (70:3:31e,16:0210c7f70584153b,10:1740036919,16:3dd80e6d867f5ad9,8:52566534,1c094fa59fa3254311c526a1fdf831ccd5e0a59c59affdf84d66b60fc7f41628)      Save this answer.  (Loading when this answer was accepted…)     (/posts/52566534/timeline)    Show activity on this post.    I ended up using Apache. In fact, it seems like there's no way to configure NGINX to send back the 408 to the client (and not just closing the connection). Patching the source is risky and makes updating the server painful.   (/a/52566534) (Short permalink to this answer) Share  Share a link to this answer     Copy link (https://creativecommons.org/licenses/by-sa/4.0/) (The current license for this post: CC BY-SA 4.0) CC BY-SA 4.0     (/posts/52566534/edit) () Improve this answer  Follow (70:3:31e,16:67c6f600c5cddc0d,10:1740036919,16:e7299b783134d0b2,8:52566534,baed3eee6ff5e29c57404d290f3c1d06812367b27156cd20804201f3c5785e7d)  Follow this answer to receive notifications       (/posts/52566534/revisions) (show all edits to this post) edited (2018-10-04 14:29:31Z) Oct 4, 2018 at 14:29         answered (2018-09-29 08:19:28Z) Sep 29, 2018 at 8:19   (/users/2700809/3v0k4) (3v0k4's user avatar)    (/users/2700809/3v0k4) 3v0k4 3v0k4 (reputation score) 161 (1 gold badge)  1  1 gold badge (4 silver badges)  4  4 silver badges (10 bronze badges)  10  10 bronze badges           (Use comments to ask for more information or suggest improvements. Avoid comments like “+1” or “thanks”.) Add a comment |  (Expand to show all comments on this post)             This answer is useful  (70:3:31e,16:1d0cbe3bce53b934,10:1740036919,16:cc3b3d0596128094,8:71178550,11e36d7c081d72670bb3dee046ba3db9674551dc5859eea862ad0dc33f7b56ec) -1  (This answer is not useful)    (70:3:31e,16:414cf625fb581fe8,10:1740036919,16:f527dd492b8bb208,8:71178550,fd87795af9742c5ec9a1e2a0ead29070e540db2dd4ec00f8e023dbed0889d3ab)      Save this answer.  (Loading when this answer was accepted…)     (/posts/71178550/timeline)    Show activity on this post.    I was running into this with a proxy_pass. Originally I had the following configuration: location / {
        proxy_read_timeout 300s;
        proxy_connect_timeout 75s;
        proxy_pass https://internal:3210/;

        add_header Access-Control-Allow-Origin *;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_buffering off;
    }   Then I commented out the proxy settings and it started to work for me: location / {
        proxy_read_timeout 300s;
        proxy_connect_timeout 75s;
        proxy_pass https://internal:3210/;

        # add_header Access-Control-Allow-Origin *;
        # proxy_http_version 1.1;
        # proxy_set_header Upgrade $http_upgrade;
        # proxy_set_header Connection "upgrade";
        # proxy_buffering off;
    }     (/a/71178550) (Short permalink to this answer) Share  Share a link to this answer     Copy link (https://creativecommons.org/licenses/by-sa/4.0/) (The current license for this post: CC BY-SA 4.0) CC BY-SA 4.0     (/posts/71178550/edit) () Improve this answer  Follow (70:3:31e,16:7e9d121a54420b64,10:1740036919,16:1c74ad0b8a1569b3,8:71178550,da0eed4c16914b22ff258b09a0634927e8de8d71a0fb238733f951a7da25dea1)  Follow this answer to receive notifications       answered (2022-02-18 18:55:37Z) Feb 18, 2022 at 18:55   (/users/1837496/charles-brandt) (Charles Brandt's user avatar)    (/users/1837496/charles-brandt) Charles Brandt Charles Brandt (reputation score) 1,087 (11 silver badges)  11  11 silver badges (13 bronze badges)  13  13 bronze badges           (Use comments to ask for more information or suggest improvements. Avoid comments like “+1” or “thanks”.) 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