Re: [quicwg/base-drafts] Discuss max-header-list-size from the other side (#2774)

ianswett <notifications@github.com> Thu, 13 June 2019 01:37 UTC

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Subject: Re: [quicwg/base-drafts] Discuss max-header-list-size from the other side (#2774)
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ianswett commented on this pull request.



> -including the length of the name and value in bytes plus an overhead of 32 bytes
-for each header field.
+An HTTP/3 implementation MAY impose a limit on the maximum size of the message
+header it will accept on an individual HTTP message.  A server that receives a
+larger header field list than it is willing to handle can send an HTTP 431
+(Request Header Fields Too Large) status code {{?RFC6585}}.  A client can
+discard responses that it cannot process.  The size of a header field list is
+calculated based on the uncompressed size of header fields, including the length
+of the name and value in bytes plus an overhead of 32 bytes for each header
+field.
+
+If an implementation wishes to advise its peer of this limit, it can be conveyed
+as a number of bytes in the `SETTINGS_MAX_HEADER_LIST_SIZE` parameter. An
+implementation which has received this parameter SHOULD NOT send an HTTP message
+header which exceeds the indicated size, as this will likely produce an error
+and could disrupt the entire connection if the peer reacts negatively.  However,

It's advisory, but I think the spirit is that eventually, this CID isn't going to route correctly.  Every deployment has this property, it's just a matter of timeframe.  

So it is advisory.  But in the same sense that GOAWAY indicates not to send new requests, this is saying "Please don't send any more packets with CIDs below this index, because it might not work."

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