Michael Brown
72db14640c
[tls] Split received records over multiple I/O buffers
TLS servers are not obliged to implement the RFC3546 maximum fragment
length extension, and many common servers (including OpenSSL, as used
in Apache's mod_ssl) do not do so. iPXE may therefore have to cope
with TLS records of up to 16kB. Allocations for 16kB have a
non-negligible chance of failing, causing the TLS connection to abort.
Fix by maintaining the received record as a linked list of I/O
buffers, rather than a single contiguous buffer. To reduce memory
pressure, we also decrypt in situ, and deliver the decrypted data via
xfer_deliver_iob() rather than xfer_deliver_raw().
Signed-off-by: Michael Brown <mcb30@ipxe.org>