[peerdist] Limit number of concurrent raw block downloads
Raw block downloads are expensive if the origin server uses HTTPS,
since each concurrent download will require local TLS resources
(including potentially large received encrypted data buffers).
Raw block downloads may also be prohibitively slow to initiate when
the origin server is using HTTPS and client certificates. Origin
servers for PeerDist downloads are likely to be running IIS, which has
a bug that breaks session resumption and requires each connection to
go through the full client certificate verification.
Limit the total number of concurrent raw block downloads to ameliorate
these problems.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[peerdist] Start block download timers from within opener methods
Move the responsibility for starting the block download timers from
peerblk_expired() to peerblk_raw_open() and peerblk_retrieval_open(),
in preparation for adding the ability to defer calls to
peerblk_raw_open() via a block download queue.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[peerdist] Gather and report peer statistics during download
Record and report the number of peers (calculated as the maximum
number of peers discovered for a block's segment at the time that the
block download is complete), and the percentage of blocks retrieved
from peers rather than from the origin server.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
[peerdist] Avoid NULL pointer dereference for plaintext blocks
Avoid accidentally dereferencing a NULL cipher context pointer for
plaintext blocks (which are usually messages with a block length of
zero, indicating a missing block).
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown