What's the maximum header size limit?

[bagder]

Version
current from master

Platform
Linux

Description
I'm using hyper in curl, and when I receive a HTTP/1 response with many response headers, hyper cuts off the response and returns an error due to message head is too large. (With a HYPERE_INVALID_PEER_MESSAGE error)

I cannot find what this exact limit is. I can't even find it in the hyper source code.

[seanmonstar]

To be more specific, are you asking about the list of headers, or the length of any single header? If receiving a lot of headers, the current limit of name/value pairs in hyper is 100. That was picked somewhat arbitrarily, and could be increased if more than that were common, but so far no one has ever needed it 🤷 .

[bagder]

Thanks for this.

I can't tell you what's right but it seems Firefox, Chrome (and curl) all accept name/value pairs all the way until they reach the maximum response header size. Which seems to be limited to somewhere between 256KB and 1MB.

[ajgh1]

I'm not sure about client-side, but Apache httpd 2.4's default LimitRequestFields (100) and LimitRequestFieldSize (8190) settings imply if a request's headers go much over 800KB, default httpd configurations will reject it. These limits can be changed of course, but the manual cautions that should not be necessary under normal circumstances.

[c-antin]

To be more specific, are you asking about the list of headers, or the length of any single header? If receiving a lot of headers, the current limit of name/value pairs in hyper is 100. That was picked somewhat arbitrarily, and could be increased if more than that were common, but so far no one has ever needed it 🤷 .

Does this MAX_HEADERS of 100 also apply for http2 requests (server-side)?
And is there a server-side size limit for each individual header including url size (for http2)?

[seanmonstar]

No, that limit is for the HTTP/1 decoder. HTTP/2 has a setting that you can send, SETTINGS_MAX_HEADER_LIST_SIZE , to tell peer how much you're willing to accept, and hyper will enforce it for you.

[f3lixding]

the current limit of name/value pairs in hyper is 100. That was picked somewhat arbitrarily, and could be increased if more than that were common, but so far no one has ever needed it

I ran into the same problem (message head is too large) for reqwest and I found my way here to this thread.
Just wanted to +1 on this. It would be fantastic if we can have the MAX_HEADERS be configurable.

[Millione]

need to be increased or can be configurable.

[PureWhiteWu]

Hi, we've encountered same problem here. Our HTTP request has 100+ headers and hyper failed with error.

Is there any plan to make it configurable?