Fixes:
commit 52a515d187
"udhcp: use poll() instead of select()"
Feb 16 2017
udhcp_sp_read() is meant to check whether signal pipe indeed has some data to read.
In the above commit, it was changed as follows:
- if (!FD_ISSET(signal_pipe.rd, rfds))
+ if (!pfds[0].revents)
return 0;
The problem is, the check was working for select() purely by accident.
Caught signal interrupts select()/poll() syscalls, they return with EINTR
(regardless of SA_RESTART flag in sigaction). _Then_ signal handler is invoked.
IOW: they can't see any changes to fd state caused by signal haldler
(in our case, signal handler makes signal pipe ready to be read).
For select(), it means that rfds[] bit array is unmodified, bit of signal
pipe's read fd is still set, and the above check "works": it thinks select()
says there is data to read.
This accident does not work for poll(): .revents stays clear, and we do not
try reading signal pipe as we should. In udhcpd, we fall through and block
in socket read. Further SIGTERM signals simply cause socket read to be
interrupted and then restarted (since SIGTERM handler has SA_RESTART=1).
Fixing this as follows: remove the check altogether. Set signal pipe read fd
to nonblocking mode. Always read it in udhcp_sp_read().
If read fails, assume it's EAGAIN and return 0 ("no signal seen").
udhcpd avoids reading signal pipe on every recvd packet by looping if EINTR
(using safe_poll()) - thus ensuring we have correct .revents for all fds -
and calling udhcp_sp_read() only if pfds[0].revents!=0.
udhcpc performs much fewer reads (typically it sleeps >99.999% of the time),
there is no need to optimize it: can call udhcp_sp_read() after each poll
unconditionally.
To robustify socket reads, unconditionally set pfds[1].revents=0
in udhcp_sp_fd_set() (which is before poll), and check it before reading
network socket in udhcpd.
TODO:
This might still fail: if pfds[1].revents=POLLIN, socket read may still block.
There are rare cases when select/poll indicates that data can be read,
but then actual read still blocks (one such case is UDP packets with
wrong checksum). General advise is, if you use a poll/select loop,
keep all your fds nonblocking.
Maybe we should also do that to our network sockets?
function old new delta
udhcp_sp_setup 55 65 +10
udhcp_sp_fd_set 54 60 +6
udhcp_sp_read 46 36 -10
udhcpd_main 1451 1437 -14
udhcpc_main 2723 2708 -15
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/3 up/down: 16/-39) Total: -23 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
When fetching a https:// URL with HTTP proxy configured
(e.g. with environment variable http_proxy=http://your-proxy:3128)
busybox was making a https connection to the proxy.
This was because the protocol scheme for the target URL was used to determine whether to connect to the proxy over SSL or not.
When the proxy is in use, the decision on whether to connect to the proxy over https
should based on the proxy URL not on the target URL.
function old new delta
wget_main 2381 2387 +6
Signed-off-by: Peter Lloyd <l-busybox@pgl22.co.uk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Attaching an interface to a VRF is done by setting the interface's
master. Besides VRF, this can also be used for bridges.
function old new delta
set_master - 142 +142
do_iplink 1262 1357 +95
packed_usage 32546 32539 -7
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 237/-7) Total: 230 bytes
Signed-off-by: Jan Luebbe <jluebbe@debian.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
VRF interfaces have a mandatory table parameter, which needs to be
specified using a RTNL attribute.
function old new delta
do_add_or_delete 1150 1254 +104
packed_usage 32444 32546 +102
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 206/0) Total: 206 bytes
Signed-off-by: Jan Luebbe <jluebbe@debian.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This way, we can zero them all in one go.
We do malloc() anyway, thus nothing is lost by mallocing "globals"
function old new delta
arping_main 1683 1686 +3
finish 100 86 -14
catcher 350 310 -40
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 3/-54) Total: -51 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ARPING 192.168.1.1 from 192.168.1.172 wlan0
Unicast reply from 192.168.1.1 [F4:F2:6D:52:A8:DE] 1.672ms
Sent 1 probes (1 broadcast(s))
Received 1 response(s)
ARPING 192.168.1.1 from 192.168.1.172 wlan0
Unicast reply from 192.168.1.1 [f4:f2:6d:52:a8:de] 1.152ms
Sent 1 probe(s) (1 broadcast(s))
Received 1 response(s) (0 request(s), 0 broadcast(s))
function old new delta
finish 120 100 -20
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Do not clear extra bits on option_mask32, it's not necessary.
Move DAD bit to 2, this makes exit logic simpler.
function old new delta
arping_main 1655 1629 -26
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Since bb_info_msg() was eliminated type of buffering on stdout is not important
function old new delta
udhcpd_main 1463 1451 -12
udhcpc_main 2735 2723 -12
setlinebuf 19 - -19
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 0/2 up/down: 0/-43) Total: -43 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
