The documentation in xfer.h and xfer.c does not say that the metadata
parameter is optional in calls such as xfer_deliver_iob_meta() and the
deliver_iob() method. However, some code in net/ is prepared to
accept a NULL pointer, and xfer_deliver_as_iob() passes a NULL pointer
directly to the deliver_iob() method.
Fix this mess of conflicting assumptions by making everything assume
that the metadata parameter is mandatory, and fixing
xfer_deliver_as_iob() to pass in a dummy metadata structure (as is
already done in xfer_deliver_iob()).
There are many functions that take ownership of the I/O buffer they
are passed as a parameter. The caller should not retain a pointer to
the I/O buffer. Use iob_disown() to automatically nullify the
caller's pointer, e.g.:
xfer_deliver_iob ( xfer, iob_disown ( iobuf ) );
This will ensure that iobuf is set to NULL for any code after the call
to xfer_deliver_iob().
iob_disown() is currently used only in places where it simplifies the
code, by avoiding an extra line explicitly setting the I/O buffer
pointer to NULL. It should ideally be used with each call to any
function that takes ownership of an I/O buffer. (The SSA
optimisations will ensure that use of iob_disown() gets optimised away
in cases where the caller makes no further use of the I/O buffer
pointer anyway.)
If gcc ever introduces an __attribute__((free)), indicating that use
of a function argument after a function call should generate a
warning, then we should use this to identify all applicable function
call sites, and add iob_disown() as necessary.
gPXE is not compliant with the HTTP/1.1 specification (RFC 2616),
since it lacks support for "Transfer-Encoding: chunked". gPXE is,
however, compliant with the HTTP/1.0 specification (RFC 1945), which
does not require "Transfer-Encoding: chunked" to be supported.
The only HTTP/1.1 feature that gPXE uses is the "Host:" header, but
servers universally accept that one from HTTP/1.0 clients as an
optional extension (it is obligatory for HTTP/1.1). gPXE does not,
for example, appear to support connection caching. Advertising as a
HTTP/1.0 client will typically make the server close the connection
immediately upon sending the last data, which is actually beneficial
if we aren't going to keep the connection alive anyway.
will enable us to cascade async operations, which is necessary in order to
properly support DNS. (For example, an HTTP request may have to redirect
to a new location and will have to perform a new DNS lookup, so we can't
just rely on doing the name lookup at the time of parsing the initial
URL).
Anything other than HTTP is probably broken right now; I'll fix the others
up asap.
