MEDIUM: buffers: add some new primitives and rework existing ones

A number of primitives were missing for buffer management, and some
of them were particularly awkward to use. Specifically, the functions
used to compute free space could not always be used depending what was
wrapping in the buffers. Some documentation has been added about how
the buffers work and their properties. Some functions are still missing
such as a buffer replacement which would support wrapping buffers.
BUG: buffers: don't return a negative value on buffer_total_space_res()

In commit 4b517ca93aaaead8aa6143aa2836dc96417653c6 (MEDIUM: buffers:
add some new primitives and rework existing ones), we forgot to check
if buffer_max_len() < l.

No backport is needed.
MINOR: buffers: make buffer_pointer() support negative pointers too

It's more handy if the buffer_pointer() function also handles negative pointers.
CLEANUP: kill buffer_replace() and use an inline instead

This function is never used, only its buffer_replace2() alternative
is used. Replace the former with an inline which calls the later.
BUG: tcp: option nolinger does not work on backends

Daniel Rankov reported that "option nolinger" is inefficient on backends.
The reason is that it is set on the file descriptor only, which does not
prevent haproxy from performing a clean shutdown() before closing. We must
set the flag on the stream_interface instead if we want an RST to be emitted
upon active close.
CLEANUP: ebtree: remove a few annoying signedness warnings

(from ebtree 6.0.6)

Care has been taken not to make the code bigger (it even got smaller
due to a possible simplification).
(cherry picked from commit 7a2c1df646049c7daac52677ec11ed63048cd150)
CLEANUP: ebtree: clarify licence and update to 6.0.6

(from ebtree 6.0.6)

This version is mainly aimed at clarifying the fact that the ebtree license
is LGPL. Some files used to indicate LGPL and other ones GPL, while the goal
clearly is to have it LGPL. A LICENSE file has also been added.

No code is affected, but it's better to have the local tree in sync anyway.

(cherry picked from commit 24dc7cca051f081600fe8232f33e55ed30e88425)
CLEANUP: ebtree: remove 4-year old harmless typo in duplicates insertion code

(from ebtree 6.0.7)

This typo has been there since we introduced duplicates. A "struct eb_troot *"
which apparently the compiler doesn't complain about while it is never declared
anywhere. Amazing...

(cherry picked from commit 2879648db5d32cf009ae571cb0e8e1df75152281)
CLEANUP: ebtree: remove another typo, a wrong initialization in insertion code

(from ebtree 6.0.7)

root_right was wrongly initialized first to <root> which is not the same
type, to be later initialized to root->b[EB_RGHT].

Let's simply remove the wrong and useless initialization.
(cherry picked from commit e63a0c2f56369b52c4d00221d83c2c4569605c06)
BUG: ebtree: ebst_lookup() could return the wrong entry

(from ebtree 6.0.7)

Julien Thomas provided a reproducible test case where a string lookup
could return the wrong node. The issue is caused by the jump to a node
which contains less bit in common than the previous node, making the
string_equal_bits() function return -1. We must not remember more bits
than the number on the node, otherwise we can be tempted to trust them
while they can change while running down.

For a valid test case, enter : "0", "WW", "W", "S", and lookup "W".
Previously, "S" was returned.

Note: string-based ebtrees are used in haproxy in ACL, peers and
stick-tables. ACLs are not affected because all patterns are
interchangeable. stick-tables are not affected because lookups are
performed using ebmb_lookup(). Only peers might be affected though
it is not easy to infirm or confirm the issue.

(cherry picked from commit dd47a54103597458887d3cc8414853a541aee9c1)
OPTIM: stream_sock: reduce the amount of in-flight spliced data

First, it's a waste not to call chk_snd() when spliced data are available,
because the pipe can almost always be transferred into the outgoing socket
buffers. Starting from now, when we splice data in, we immediately try to
send them. This results in less pipes used, and possibly less kernel memory
in use at once.

Second, if a pipe cannot be transferred into the outgoing socket buffers,
it means this buffer is full. There's no point trying again then, as space
will almost never be available, resulting in a useless syscall returning
EAGAIN.
OPTIM: stream_sock: save a failed recv syscall when splice returns EAGAIN

When splice() returns EAGAIN, on old kernels it could be caused by a read
shutdown which was not detected. Due to this behaviour, we had to fall
back to recv(), which in turn says if it's a real EAGAIN or a shutdown.
Since this behaviour was fixed in 2.6.27.14, on more recent kernels we'd
prefer to avoid the fallback to recv() when possible. For this, we set a
variable the first time splice() detects a shutdown, to indicate that it
works. We can then rely on this variable to adjust our behaviour.

Doing this alone increased the overall performance by about 1% on medium
sized objects.
MINOR: acl: add support for TLS server name matching using SNI

Server Name Indication (SNI) is a TLS extension which makes a client
present the name of the server it is connecting to in the client hello.
It allows a transparent proxy to take a decision based on the beginning
of an SSL/TLS stream without deciphering it.

The new ACL "req_ssl_sni" matches the name extracted from the TLS
handshake against a list of names which may be loaded from a file if
needed.
BUG: http: re-enable TCP quick-ack upon incomplete HTTP requests

By default we disable TCP quick-acking on HTTP requests so that we
avoid sending a pure ACK immediately followed by the HTTP response.
However, if the client sends an incomplete request in a short packet,
its TCP stack might wait for this packet to be ACKed before sending
the rest of the request, delaying incoming requests by up to 40-200ms.

We can detect this undesirable situation when parsing the request :
  - if an incomplete request is received
  - if a full request is received and uses chunked encoding or advertises
    a content-length larger than the data available in the buffer

In these situations, we re-enable TCP quick-ack if we had previously
disabled it.
BUG: proto_tcp: don't try to bind to a foreign address if sin_family is unknown

This is 1.5-specific. It causes issues with transparent source binding involving
hdr_ip. We must not try to bind() to a foreign address when the family is not set,
and we must set the family when an address is set.
MINOR: pattern: export the global temporary pattern

The global pattern is used for pattern conversions. Export it under the
name "temp_pattern" so that it can later be used by ACLs.
CLEANUP: patterns: get rid of pattern_data_setstring()

This function was only used to call chunk_init_len() from another chunk,
which in the end consists in simply assigning the source chunk to the
destination chunk. Let's remove this indirection to make the code clearer.
Anyway it was the only place such a function was used.
MEDIUM: acl: use temp_pattern to store fetched information in the "method" match

This match was using both the int and ptr part of the acl_test struct. Let's
change this to be able to store it into a chunk with a special encoding.
MINOR: acl: include pattern.h to make pattern migration more transparent
MEDIUM: pattern: change the pattern data integer from unsigned to signed

Till now the pattern data integer type was unsigned without any
particular reason. In order to make ACLs use it, we must switch it
to signed int instead.