Ryan O'Hara reported that haproxy breaks on fedora-32 using gcc-10
(pre-release). It turns out that constructs such as:
while (item != head) {
item = LIST_ELEM(item.n);
}
loop forever, never matching <item> to <head> despite a printf there
showing them equal. In practice the problem is that the LIST_ELEM()
macro is wrong, it assigns the subtract of two pointers (an integer)
to another pointer through a cast to its pointer type. And GCC 10 now
considers that this cannot match a pointer and silently optimizes the
comparison away. A tested workaround for this is to build with
-fno-tree-pta. Note that older gcc versions even with -ftree-pta do
not exhibit this rather surprizing behavior.
This patch changes the test to instead cast the null-based address to
an int to get the offset and subtract it from the pointer, and this
time it works. There were just a few places to adjust. Ideally
offsetof() should be used but the LIST_ELEM() API doesn't make this
trivial as it's commonly called with a typeof(ptr) and not typeof(ptr*)
thus it would require to completely change the whole API, which is not
something workable in the short term, especially for a backport.
With this change, the emitted code is subtly different even on older
versions. A code size reduction of ~600 bytes and a total executable
size reduction of ~1kB are expected to be observed and should not be
taken as an anomaly. Typically this loop in dequeue_proxy_listeners() :
while ((listener = MT_LIST_POP(...)))
used to produce this code where the comparison is performed on RAX
while the new offset is assigned to RDI even though both are always
identical:
53ded8: 48 8d 78 c0 lea -0x40(%rax),%rdi
53dedc: 48 83 f8 40 cmp $0x40,%rax
53dee0: 74 39 je 53df1b <dequeue_proxy_listeners+0xab>
and now produces this one which is slightly more efficient as the
same register is used for both purposes:
53dd08: 48 83 ef 40 sub $0x40,%rdi
53dd0c: 74 2d je 53dd3b <dequeue_proxy_listeners+0x9b>
Similarly, retrieving the channel from a stream_interface using si_ic()
and si_oc() used to cause this (stream-int in rdi):
1cb7: c7 47 1c 00 02 00 00 movl $0x200,0x1c(%rdi)
1cbe: f6 47 04 10 testb $0x10,0x4(%rdi)
1cc2: 74 1c je 1ce0 <si_report_error+0x30>
1cc4: 48 81 ef 00 03 00 00 sub $0x300,%rdi
1ccb: 81 4f 10 00 08 00 00 orl $0x800,0x10(%rdi)
and now causes this:
1cb7: c7 47 1c 00 02 00 00 movl $0x200,0x1c(%rdi)
1cbe: f6 47 04 10 testb $0x10,0x4(%rdi)
1cc2: 74 1c je 1ce0 <si_report_error+0x30>
1cc4: 81 8f 10 fd ff ff 00 orl $0x800,-0x2f0(%rdi)
There is extremely little chance that this fix wakes up a dormant bug as
the emitted code effectively does what the source code intends.
This must be backported to all supported branches (dropping MT_LIST_ELEM
and the spoa_example parts as needed), since the bug is subtle and may
not always be visible even when compiling with gcc-10.
I found on an (old) AIX 5.1 machine that stdint.h didn't exist while
inttypes.h which is expected to include it does exist and provides the
desired functionalities.
As explained here, stdint being just a subset of inttypes for use in
freestanding environments, it's probably always OK to switch to inttypes
instead:
https://pubs.opengroup.org/onlinepubs/009696799/basedefs/stdint.h.html
Also it's even clearer here in the autoconf doc :
https://www.gnu.org/software/autoconf/manual/autoconf-2.61/html_node/Header-Portability.html
"The C99 standard says that inttypes.h includes stdint.h, so there's
no need to include stdint.h separately in a standard environment.
Some implementations have inttypes.h but not stdint.h (e.g., Solaris
7), but we don't know of any implementation that has stdint.h but not
inttypes.h"
When the connection is closed by HAProxy, the status code provided in the
DISCONNECT frame is lost. By retransmitting it in the agent's reply, we are sure
to have it in the SPOE logs.
This patch may be backported in 1.8.
The commit c4dcaff3 ("BUG/MEDIUM: spoe: Flags are not encoded in network order")
introduced an incompatibility with older agents. So the major version of the
SPOP is increased to make the situation unambiguous. And because before the fix,
the protocol is buggy, the support of the version 1.0 is removed to be sure to
not continue to support buggy agents.
The agents in the contrib folder (spoa_example, modsecurity and mod_defender)
are also updated to announce the SPOP version 2.0.
So, to be clear, from the patch, connections to agents announcing the SPOP
version 1.0 will be rejected.
This patch must be backported in 1.8.
Buf is unsigned, so nbargs will be negative for more then 127 args.
Note that I cant test this bug because I cant put sufficient args
on the configuration line. It is just detected reading code.
[wt: this can be backported to 1.8 & 1.7]
Being an external agent, it's confusing that it uses haproxy's internal
types and it seems to have encouraged other implementations to do so.
Let's completely remove any reference to struct sample and use the
native DATA types instead of converting to and from haproxy's sample
types.
The same buffer is used for a request and its response. So we need to be sure
to correctly reset info when the response is encoded. And here there was a
bug. The pointer on the end of the frame was not updated. So it was not
possible to encode a response bigger than the corresponding request.
These encoding functions does general stuff and can be used in
other context than spoe. This patch moves the function spoe_encode_varint
and spoe_decode_varint from spoe to common. It also remove the prefix spoe.
These functions will be used for encoding values in new binary sample fetch.
Now, when a payload is fragmented, the first frame must define the frame type
and the followings must use the special type SPOE_FRM_T_UNSET. This way, it is
easy to know if a fragment is the first one or not. Of course, all frames must
still share the same stream-id and frame-id.
Update SPOA example accordingly.
If an agent want to abort the processing a fragmented NOTIFY frame before
receiving all fragments, it can send an ACK frame at any time with ABORT bit set
(and of course, the FIN bit too).
Beside this change, SPOE_FRM_ERR_FRAMEID_NOTFOUND error flag has been added. It
is set when a unknown ACK frame is received.
Now, we can use the option '-c' to enable the support of a capability. By
default, all capabilities are disabled. For example:
$> ./spoa -c async -c pipelining
In addition, it is also possible to set the maximum frame size supported by your
agent (-m) and to add a delay in frames processing (-t).
A new "option spop-check" statement has been added to enable server health
checks based on SPOP HELLO handshake. SPOP is the protocol used by SPOE filters
to talk to servers.
This is a very simple service that implement a "random" ip reputation
service. It will return random scores for all checked IP addresses. It only
shows you how to implement a ip reputation service or such kind of services
using the SPOE.
