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My experience with the RT-AC86U

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So would you recommend letting the script lock up... then running an strace on the hung "nvram get" PID to examine the hung process further?
 
Code: 
bind(3, {sa_family=AF_NETLINK, nl_pid=1098, nl_groups=00000000}, 12) = -1 EADDRINUSE (Address already in use)
The difference.
 
dave14305 said:
I ran watch -n 0 strace -r nvram get wan0_enable
Click to expand...
I guess I could run 5 different watch windows to monitor each of the vpnclient# state nvram values to see which one it randomly hangs on?
 
Well... I dunno. I didn't see a way to control the output of this strace info... it was flying across my screen. The vpn_client3_state locked, but the strace window monitoring that nvram command just kept on going. Not quite sure how to handle this.
 
Viktor Jaep said:
Well... I dunno. I didn't see a way to control the output of this strace info... it was flying across my screen. The vpn_client3_state locked, but the strace window monitoring that nvram command just kept on going. Not quite sure how to handle this.
Click to expand...
It will keep redrawing until the watched command hangs. I wasn’t getting anywhere with a 1 second interval so I went to 0. But that makes it harder to stop the watch loop when you want to ctrl-c. It ends the hung nvram command and starts a new one. So I kill the watch pid in another window and copy/paste the last output in the other window.
 
dave14305 said:
It will keep redrawing until the watched command hangs. I wasn’t getting anywhere with a 1 second interval so I went to 0. But that makes it harder to stop the watch loop when you want to ctrl-c. It ends the hung nvram command and starts a new one. So I kill the watch pid in another window and copy/paste the last output in the other window.
Click to expand...
Yeah, I was not able to ctrl-c out of that...
 
Here's an example of an nvram wrapper. Realize I quite literally threw this together a few minutes ago. So it might need some refinement. But I just wanted to provide a quick-n-dirty example.

Bash: 
#!/bin/sh

# copy original nvram executable to /tmp
cp /usr/sbin/nvram /tmp/_nvram

# create nvram wrapper that calls original nvram executable in /tmp
cat << 'EOF' > /tmp/nvram
#!/bin/sh
#set -x # comment/uncomment to disable/enable debug mode

# required for serialization when reentry is possible
LOCK="/tmp/$(basename $0).lock"
acquire_lock() { until mkdir $LOCK &>/dev/null; do sleep 2; done; }
release_lock() { rmdir $LOCK &>/dev/null; }

# one instance at a time
acquire_lock

# catch premature exit and cleanup
trap 'release_lock; exit 1' SIGHUP SIGINT SIGTERM

/tmp/_nvram $@

rc=$?

# any concurrent instance(s) may now run
release_lock

exit $rc
EOF
chmod +x /tmp/nvram

# replace nvram in /usr/sbin w/ nvram wrapper in /tmp
mount -o bind /tmp/nvram /usr/sbin/nvram

The idea is to FORCE every reference to the nvram executable threw the above script, which enforces one-at-a-time semantics.
 
Last edited:
I repeated the test with a wl command and it sees the same address in use message when it hangs.
Code: 
Every 0s: strace -r wl -i eth5 noise                                                                       2022-06-14 20:07:33

     0.000000 execve("/usr/sbin/wl", ["wl", "-i", "eth5", "noise"], 0x7fe50f5f30 /* 18 vars */ <unfinished ...>
     0.000662 [ Process PID=1163 runs in 32 bit mode. ]
strace: WARNING: Proper structure decoding for this personality is not supported, please consider building strace with mpers support enabled.
     0.000040 <... execve resumed>)     = 0
     0.000066 brk(NULL)                 = 0x82f000
     0.000057 uname({sysname="Linux", nodename="router", ...}) = 0
     0.000096 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf72fa000
     0.000064 access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
     0.000127 open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
     0.000068 fstat64(3, 0xffd6d570)    = 0
     0.000319 mmap2(NULL, 10528, PROT_READ, MAP_PRIVATE, 3, 0) = 0xf72f7000
     0.000044 close(3)                  = 0
     0.000053 open("/lib/libnvram.so", O_RDONLY|O_CLOEXEC) = 3
     0.000050 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\08\t\0\0004\0\0\0"..., 512) = 512
     0.000051 fstat64(3, 0xffd6d5b0)    = 0
     0.000041 mmap2(NULL, 69528, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf72bb000
     0.000047 mprotect(0xf72bc000, 61440, PROT_NONE) = 0
     0.000049 mmap2(0xf72cb000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0) = 0xf72cb000
     0.000058 close(3)                  = 0
     0.000045 open("/lib/libwlcsm.so", O_RDONLY|O_CLOEXEC) = 3
     0.000048 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\200\34\0\0004\0\0\0"..., 512) = 512
     0.000047 fstat64(3, 0xffd6d598)    = 0
     0.000038 mmap2(NULL, 90092, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf72a5000
     0.000044 mprotect(0xf72aa000, 61440, PROT_NONE) = 0
     0.000046 mmap2(0xf72b9000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x4000) = 0xf72b9000
     0.000067 close(3)                  = 0
     0.000046 open("/usr/lib/libshared.so", O_RDONLY|O_CLOEXEC) = 3
     0.000050 read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\214X\1\0004\0\0\0"..., 512) = 512
     0.000048 fstat64(3, 0xffd6d580)    = 0
     0.000038 mmap2(NULL, 646528, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf7207000
     0.000044 mprotect(0xf7274000, 65536, PROT_NONE) = 0
     0.000047 mmap2(0xf7284000, 45056, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x6d000) = 0xf7284000
     0.000059 mmap2(0xf728f000, 89472, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf728f000
     0.000060 close(3)                  = 0
     0.000054 open("/lib/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
     0.000047 read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0xm\1\0004\0\0\0"..., 512) = 512
     0.000048 fstat64(3, 0xffd6d568)    = 0
     0.000038 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf72f6000
     0.000047 mmap2(NULL, 1299824, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf70c9000
     0.000045 mprotect(0xf71f1000, 65536, PROT_NONE) = 0
     0.000052 mmap2(0xf7201000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x128000) = 0xf7201000
     0.000059 mmap2(0xf7204000, 9584, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf7204000
     0.000056 close(3)                  = 0
     0.000061 open("/lib/libpthread.so.0", O_RDONLY|O_CLOEXEC) = 3
     0.000050 read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\\I\0\0004\0\0\0"..., 512) = 512
     0.000048 fstat64(3, 0xffd6d460)    = 0
     0.000038 mmap2(NULL, 164436, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf70a0000
     0.000045 mprotect(0xf70b5000, 65536, PROT_NONE) = 0
     0.000050 mmap2(0xf70c5000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15000) = 0xf70c5000
     0.000060 mmap2(0xf70c7000, 4692, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf70c7000
     0.000055 close(3)                  = 0
     0.000073 mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf72f5000
     0.000048 set_tls(0xf72f54c0)       = 0
     0.000257 mprotect(0xf7201000, 8192, PROT_READ) = 0
     0.000088 mprotect(0xf70c5000, 4096, PROT_READ) = 0
     0.000298 mprotect(0xf72fb000, 4096, PROT_READ) = 0
     0.000051 munmap(0xf72f7000, 10528) = 0
     0.000050 set_tid_address(0xf72f5068) = 1163
     0.000036 set_robust_list(0xf72f5070, 12) = 0
     0.000052 rt_sigaction(SIGRTMIN, {sa_handler=0xf70a4278, sa_mask=[], sa_flags=SA_RESTORER|SA_SIGINFO, sa_restorer=0xf70f5b10}, NULL, 8) = 0
     0.000063 rt_sigaction(SIGRT_1, {sa_handler=0xf70a435c, sa_mask=[], sa_flags=SA_RESTORER|SA_RESTART|SA_SIGINFO, sa_restorer=0xf70f5b10}, NULL, 8) = 0
     0.000064 rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
     0.000059 ugetrlimit(RLIMIT_STACK, {rlim_cur=2048*1024, rlim_max=RLIM_INFINITY}) = 0
     0.000215 socket(AF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
     0.000077 ioctl(3, SIOCDEVPRIVATE, 0xffd6db00) = 0
     0.000257 close(3)                  = 0
     0.000055 socket(AF_INET, SOCK_DGRAM, IPPROTO_IP) = 3
     0.000041 ioctl(3, SIOCDEVPRIVATE, 0xffd6db00) = 0
     0.000149 close(3)                  = 0
     0.000069 stat64("/jffs", 0xffd6d9a8) = 0
     0.000055 stat64("/jffs/nvram_war", 0xffd6d9a8) = 0
     0.000086 socket(AF_NETLINK, SOCK_RAW, 0x1f /* NETLINK_??? */) = 3
     0.000055 bind(3, {sa_family=AF_NETLINK, nl_pid=1163, nl_groups=00000000}, 12) = -1 EADDRINUSE (Address already in use)
     0.000137 brk(NULL)                 = 0x82f000
     0.000038 brk(0x850000)             = 0x850000
     0.000056 sendmsg(3, {msg_name=0xcffd6da38, msg_namelen=-2696656, msg_iov=NULL, msg_iovlen=0, msg_control=0xf72b9d7400090dd4, msg_controllen=3505436194745028, msg_flags=MSG_WAITALL|MSG_FIN|MSG_CONFIRM|MSG_RST|MSG_NOSIGNAL|MSG_MORE|MSG_SENDPAGE_NOTLAST|MSG_BATCH|MSG_ZEROCOPY|MSG_FASTOPEN|MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT|0x1bd00000}, 0) = 36
     0.000148 recvmsg(3,
 
@Viktor Jaep if you are up for one more test then here is an interesting one to test concurrency.

Code: 
#!/bin/sh
trap '' HUP INT QUIT ABRT TERM
(i="0"
while true; do
  i="$(( i + 1 ))";
  for nv in 1 2 3 4 5; do
    unset "state${nv}";
    [ "$(ps -T | grep "nvram get" | wc -l )" -le "1" ] && eval "state${nv}"="$(/bin/nvram get vpn_client${nv}_state)";
  done
  clear
  echo "$state1" "$state2" "$state3" "$state4" "$state5"
  echo "$i"
done) > /tmp/mynvramerror.log 2>&1 &
exit 0
 
eibgrad said:
Here's an example of an nvram wrapper. Realize I quite literally threw this together a few minutes ago. So it might need some refinement. But I just wanted to provide a quick-n-dirty example.

Bash: 
#!/bin/sh

# copy original nvram executable to /tmp
cp /usr/sbin/nvram /tmp/_nvram

# create nvram wrapper that calls original nvram executable in /tmp
cat << 'EOF' > /tmp/nvram
#!/bin/sh
#set -x # comment/uncomment to disable/enable debug mode

# required for serialization when reentry is possible
LOCK="/tmp/$(basename $0).lock"
acquire_lock() { until mkdir $LOCK &>/dev/null; do sleep 2; done; }
release_lock() { rmdir $LOCK &>/dev/null; }

# one instance at a time
acquire_lock

# catch premature exit and cleanup
trap 'release_lock; exit 1' SIGHUP SIGINT SIGTERM

/tmp/_nvram $@

rc=$?

# any concurrent instance(s) may now run
release_lock

exit $rc
EOF
chmod +x /tmp/nvram

# replace nvram in /usr/sbin w/ nvram wrapper in /tmp
mount -o bind /tmp/nvram /usr/sbin/nvram

The idea is to FORCE every reference to the nvram executable threw the above script, which enforces one-at-a-time semantics.
Click to expand...
I figured you were going to go into lock file semantics, but mine are much simpler. However here we are talking about concurrent runs of nvram from separate parents and process's. therefore wouldn't our lock need to be applied to nvram process itself and not just the wrapper for one parent process?
 
SomeWhereOverTheRainBow said:
I figured you were going to go into lock file semantics, but mine are much simpler. However here we are talking about concurrent runs of nvram from separate parents and process's. therefore wouldn't our lock need to be applied to nvram process itself?
Click to expand...

If the parent process (nvram script) is serialized, then so is the child process (nvram executable).
 
eibgrad said:
If the parent process (nvram script) is serialized, then so is the child process (nvram executable).
Click to expand...
That is if we account for the path of nvram to be to the serialized process? Help me here I am only trying to understand. I use something similar to manage one of my loops.


Code: 
AdGuardHome_Run () {
  local lock_dir
  local pid_file
  lock_dir="/tmp/AdGuardHome"
  pid_file="${lock_dir}/pid"
  if ( mkdir ${lock_dir} ) 2> /dev/null; then
    printf "%s\n" "$$" > $pid_file
    trap 'rm -rf "$lock_dir"; exit $?' EXIT
    start="$(date +%s)"
    $1
    end="$(date +%s)"
    runtime="$((end-start))"
    logger -st "$NAME" "$1 took $runtime second(s) to complete."
    rm -rf "$lock_dir"
  else
    logger -st "$NAME" "Lock owned by $(cat $pid_file) exists; preventing duplicate runs!"
  fi
}
 
That is if we account for the path of nvram to be to the serialized process? Help me here I am only trying to understand. I use something similar to manage one of my loops.
SomeWhereOverTheRainBow said:
Code: 
AdGuardHome_Run () {
  local lock_dir
  local pid_file
  lock_dir="/tmp/AdGuardHome"
  pid_file="${lock_dir}/pid"
  if ( mkdir ${lock_dir} ) 2> /dev/null; then
    printf "%s\n" "$$" > $pid_file
    trap 'rm -rf "$lock_dir"; exit $?' EXIT
    start="$(date +%s)"
    $1
    end="$(date +%s)"
    runtime="$((end-start))"
    logger -st "$NAME" "$1 took $runtime second(s) to complete."
    rm -rf "$lock_dir"
  else
    logger -st "$NAME" "Lock owned by $(cat $pid_file) exists; preventing duplicate runs!"
  fi
}
Click to expand...

What I'm serializing is the ability to create the lock, which is the directory /tmp/nvram.lock. That's an atomic operation.
 
eibgrad said:
That is if we account for the path of nvram to be to the serialized process? Help me here I am only trying to understand. I use something similar to manage one of my loops.


What I'm serializing is the ability to create the lock, which is the directory /tmp/nvram.lock. That's an atomic operation.
Click to expand...
Now you are being more precise. I appreciate it. You cleared it up more.
 
eibgrad said:
That is if we account for the path of nvram to be to the serialized process? Help me here I am only trying to understand. I use something similar to manage one of my loops.


What I'm serializing is the ability to create the lock, which is the directory /tmp/nvram.lock. That's an atomic operation.
Click to expand...
I use a similar method to limit how many times my adguardhome can be called to start from a loop. I only wish the routers allowed trapping of the 'ERR'
 
SomeWhereOverTheRainBow said:
@Viktor Jaep if you are up for one more test then here is an interesting one to test concurrency.

Code: 
#!/bin/sh
trap '' HUP INT QUIT ABRT TERM
(i="0"
while true; do
  i="$(( i + 1 ))";
  for nv in 1 2 3 4 5; do
    unset "state${nv}";
    [ "$(ps -T | grep "nvram get" | wc -l )" -le "1" ] && eval "state${nv}"="$(/bin/nvram get vpn_client${nv}_state)";
  done
  clear
  echo "$state1" "$state2" "$state3" "$state4" "$state5"
  echo "$i"
done) > /tmp/mynvramerror.log 2>&1 &
exit 0
Click to expand...
Well, that's a weird one... not quite sure if it worked correctly or not... but for most of the log, each line was blank... Every so often, you would see an indication that it tried to do an nvram get call:

1655255440862.png
 
Viktor Jaep said:
Well, that's a weird one... not quite sure if it worked correctly or not... but for most of the log, each line was blank... Every so often, you would see an indication that it tried to do an nvram get call:

View attachment 41881
Click to expand...
maybe the CPU timing is wrong.. Something is seriously wrong if it cannot get past that.

try this?

Code: 
#!/bin/sh
trap '' HUP INT QUIT ABRT TERM
(i="0"
while true; do
  i="$(( i + 1 ))";
  for nv in 1 2 3 4 5; do
    unset "state${nv}";
    [ "$(ps -T | grep "nvram get" | wc -l )" -le "2" ] && eval "state${nv}"="$(/bin/nvram get vpn_client${nv}_state)";
  done
  clear
  echo "$state1" "$state2" "$state3" "$state4" "$state5"
  echo "$i"
done) > /tmp/mynvramerror.log 2>&1 &
exit 0

or

Code: 
#!/bin/sh
trap '' HUP INT QUIT ABRT TERM
(i="0"
until [ "$(ps -T | grep "nvram get" | wc -l )" -gt "2" ]; do
  i="$(( i + 1 ))";
  for nv in 1 2 3 4 5; do
    unset "state${nv}";
    [ "$(ps -T | grep "nvram get" | wc -l )" -le "2" ] && eval "state${nv}"="$(/bin/nvram get vpn_client${nv}_state)";
  done
  clear
  echo "$state1" "$state2" "$state3" "$state4" "$state5"
  echo "$i"
done) > /tmp/mynvramerror.log 2>&1 &
exit 0
 
Last edited:
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