code review 4628063: http: better handling of 0-length Request.Body

http: better handling of 0-length Request.Body

As rsc suggested after change 58a6bdac3d12 was committed, we
now read the first byte of Request.Body when the
Request.ContentLength is 0 to disambiguate between a truly
zero-length body and a body of unknown length where the user
didn't set the ContentLength field.

This was also causing the reverse proxy problem where incoming
requests (which always have a body, of private type http.body,
even for 0-lengthed requests) were being relayed to the http
Transport for fetching, which was serializing the request as a
chunked request (since ContentLength was 0 and Body was
non-nil)

Fixes issue 1999

[bradfitz, 2011-06-24 22:26:00]

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://go.googlecode.com/hg

[kevlar, 2011-06-24 23:19:44]

LGTM

http://codereview.appspot.com/4628063/diff/2005/src/pkg/http/transfer.go
File src/pkg/http/transfer.go (right):

http://codereview.appspot.com/4628063/diff/2005/src/pkg/http/transfer.go#newc...
src/pkg/http/transfer.go:55: t.Body = io.MultiReader(bytes.NewBuffer(buf[:]),
t.Body)
I assume, based on your comment elsewhere, that we don't think making this a
buffered reader would be a net win over the extra 5 characters required for the
extra chunk?

[bradfitz, 2011-06-24 23:25:43]

http://codereview.appspot.com/4628063/diff/2005/src/pkg/http/transfer.go
File src/pkg/http/transfer.go (right):

http://codereview.appspot.com/4628063/diff/2005/src/pkg/http/transfer.go#newc...
src/pkg/http/transfer.go:55: t.Body = io.MultiReader(bytes.NewBuffer(buf[:]),
t.Body)
On 2011/06/24 23:19:45, kevlar wrote:
> I assume, based on your comment elsewhere, that we don't think making this a
> buffered reader would be a net win over the extra 5 characters required for
the
> extra chunk?

Doing it here would fix it for just one case.  I'd rather solve it generically
for all readers.

Our current output is very chunk-heavy, but that's a separate issue.

[bradfitz, 2011-06-24 23:46:23]

*** Submitted as http://code.google.com/p/go/source/detail?r=59f3e8fcb8da ***

http: better handling of 0-length Request.Body

As rsc suggested after change 58a6bdac3d12 was committed, we
now read the first byte of Request.Body when the
Request.ContentLength is 0 to disambiguate between a truly
zero-length body and a body of unknown length where the user
didn't set the ContentLength field.

This was also causing the reverse proxy problem where incoming
requests (which always have a body, of private type http.body,
even for 0-lengthed requests) were being relayed to the http
Transport for fetching, which was serializing the request as a
chunked request (since ContentLength was 0 and Body was
non-nil)

Fixes issue 1999

R=golang-dev, kevlar
CC=golang-dev
http://codereview.appspot.com/4628063