Tiny Core Extensions > TCE Tips & Tricks

preventing dropped wifi connections [SOLVED]

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GNUser:
PROBLEM:
I was experiencing unexplained dropped wifi connections when using my Pure64 10.1 laptop at work. The place where I work has a complex network that's open (no password) and has thousands of clients connected at the same time. My guess is that it uses IPv6 to some extent, but I can't say for sure. My laptop has an Atheros wireless card (AR928X per lshw) and, per iwconfig and cat /sys/module/ath9k/parameters/ps_enable, "power management" is off.

The only output I could find at time of dropped connections were single lines in output of dmesg, either this:


--- Code: ---wlan0: deauthenticating from <mac address> by local choice (Reason: 1=UNSPECIFIED)

--- End code ---
or this: 

--- Code: ---wlan0: deauthenticating from <mac address> by local choice (Reason: 3=DEAUTH_LEAVING)

--- End code ---

Not very helpful.

My setup when I was experiencing the dropped connections: IPv6 disabled (ipv6-4.16.10-tinycore64.tcz was not loaded), iwconfig to connect to open networks, udhcpc as DCHP client. This was the key part of my autowifi script (which runs with root privileges):


--- Code: ---ssid=WorkplaceOpen
iface=wlan0

iwconfig wlan0 essid "$ssid" &
sleep 3
udhcpc -i $iface

--- End code ---

SOLUTION:
Since I wasn't finding any specific clues as to the nature of the problem, I thought I'd throw everything but the kitchen sink at it: IPv6 enabled, wpa_supplicant to connect to open networks as well as encrypted ones, dhclient as DHCP client.

To support the new approach, I needed to install two additional extensions:

--- Code: ---tce-load -wi ipv6-4.19.10-tinycore64 dhcp

--- End code ---

dhclient is quite fussy compared to udhcpc: It needs a) a configuration file, b) a script to run after it does some initial work, and c) an empty directory in which to save details of current leases.

a) Here is the configuration file, /etc/dhcp/dhclient.conf, which I cobbled together by cheating and seeing what NetworkManager uses when running in Devuan:

--- Code: ---option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
option ms-classless-static-routes code 249 = array of unsigned integer 8;
option wpad code 252 = string;

send host-name = gethostname();

request subnet-mask, broadcast-address, time-offset, routers,
domain-search, domain-name-servers, host-name,
dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
netbios-name-servers, netbios-scope, interface-mtu,
rfc3442-classless-static-routes, ntp-servers, ms-classless-static-routes, wpad;
--- End code ---

b) Here is /sbin/dhclient-script, which I copied from Devuan:

--- Code: ---#!/bin/sh

# dhclient-script for Linux. Dan Halbert, March, 1997.
# Updated for Linux 2.[12] by Brian J. Murrell, January 1999.
# Modified for Debian.  Matt Zimmerman and Eloy Paris, December 2003
# Modified to remove useless tests for antiquated kernel versions that
# this doesn't even work with anyway, and introduces a dependency on /usr
# being mounted, which causes cosmetic errors on hosts that NFS mount /usr
# Andrew Pollock, February 2005
# Modified to work on point-to-point links. Andrew Pollock, June 2005
# Modified to support passing the parameters called with to the hooks. Andrew Pollock, November 2005
# Modified to work on Busybox, whose chown and chmod applets do not have the '--reference' flag. GNUser, November 2019

# The alias handling in here probably still sucks. -mdz

# wait for given file to be writable
wait_for_rw() {
    local file=$1
    # Find out whether we are going to mount / rw
    exec 9>&0 </etc/fstab
    rootmode=rw
    while read dev mnt type opts dump pass junk; do
        [ "$mnt" != / ] && continue
        case "$opts" in
            ro|ro,*|*,ro|*,ro,*)
               rootmode=ro
               ;;
             esac
     done
     exec 0>&9 9>&-

    # Wait for $file to become writable
    if [ "$rootmode" = "rw" ]; then
        while ! { : >> "$file"; } 2>/dev/null; do
            sleep 0.1
        done
    fi
}

# update /etc/resolv.conf based on received values
make_resolv_conf() {
    local new_resolv_conf

    # DHCPv4
    if [ -n "$new_domain_search" ] || [ -n "$new_domain_name" ] ||
       [ -n "$new_domain_name_servers" ]; then
        resolv_conf=$(readlink -f "/etc/resolv.conf" 2>/dev/null) ||
            resolv_conf="/etc/resolv.conf"

        new_resolv_conf="${resolv_conf}.dhclient-new.$$"
        wait_for_rw "$new_resolv_conf"
        rm -f $new_resolv_conf

        if [ -n "$new_domain_name" ]; then
            echo domain ${new_domain_name%% *} >>$new_resolv_conf
        fi

        if [ -n "$new_domain_search" ]; then
            if [ -n "$new_domain_name" ]; then
                domain_in_search_list=""
                for domain in $new_domain_search; do
                    if [ "$domain" = "${new_domain_name}" ] ||
                       [ "$domain" = "${new_domain_name}." ]; then
                        domain_in_search_list="Yes"
                    fi
                done
                if [ -z "$domain_in_search_list" ]; then
                    new_domain_search="$new_domain_name $new_domain_search"
                fi
            fi
            echo "search ${new_domain_search}" >> $new_resolv_conf
        elif [ -n "$new_domain_name" ]; then
            echo "search ${new_domain_name}" >> $new_resolv_conf
        fi

        if [ -n "$new_domain_name_servers" ]; then
            for nameserver in $new_domain_name_servers; do
                echo nameserver $nameserver >>$new_resolv_conf
            done
        else # keep 'old' nameservers
            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p $resolv_conf >>$new_resolv_conf
        fi

if [ -f $resolv_conf ]; then
    #chown --reference=$resolv_conf $new_resolv_conf
    chown root:root $new_resolv_conf
    #chmod --reference=$resolv_conf $new_resolv_conf
    chmod 644 $new_resolv_conf
fi
        mv -f $new_resolv_conf $resolv_conf
    # DHCPv6
    elif [ -n "$new_dhcp6_domain_search" ] || [ -n "$new_dhcp6_name_servers" ]; then
        resolv_conf=$(readlink -f "/etc/resolv.conf" 2>/dev/null) ||
            resolv_conf="/etc/resolv.conf"

        new_resolv_conf="${resolv_conf}.dhclient-new.$$"
        wait_for_rw "$new_resolv_conf"
        rm -f $new_resolv_conf

        if [ -n "$new_dhcp6_domain_search" ]; then
            echo "search ${new_dhcp6_domain_search}" >> $new_resolv_conf
        fi

        if [ -n "$new_dhcp6_name_servers" ]; then
            for nameserver in $new_dhcp6_name_servers; do
                # append %interface to link-local-address nameservers
                if [ "${nameserver##fe80::}" != "$nameserver" ] ||
                   [ "${nameserver##FE80::}" != "$nameserver" ]; then
                    nameserver="${nameserver}%${interface}"
                fi
                echo nameserver $nameserver >>$new_resolv_conf
            done
        else # keep 'old' nameservers
            sed -n /^\w*[Nn][Aa][Mm][Ee][Ss][Ee][Rr][Vv][Ee][Rr]/p $resolv_conf >>$new_resolv_conf
        fi

if [ -f $resolv_conf ]; then
            #chown --reference=$resolv_conf $new_resolv_conf
            chown root:root $new_resolv_conf
            #chmod --reference=$resolv_conf $new_resolv_conf
            chmod 644 $new_resolv_conf
fi
        mv -f $new_resolv_conf $resolv_conf
    fi
}

# set host name
set_hostname() {
    if [ -n "$new_host_name" ]; then
        local current_hostname=$(hostname)

        # current host name is empty, '(none)' or 'localhost' or differs from new one from DHCP
        if [ -z "$current_hostname" ] ||
           [ "$current_hostname" = '(none)' ] ||
           [ "$current_hostname" = 'localhost' ] ||
           [ "$current_hostname" = "$old_host_name" ]; then
           if [ "$new_host_name" != "$current_host_name" ]; then
               hostname "$new_host_name"
           fi
        fi
    fi
}

# run given script
run_hook() {
    local script="$1"
    local exit_status=0

    if [ -f $script ]; then
        . $script
        exit_status=$?
    fi

    if [ -n "$exit_status" ] && [ "$exit_status" -ne 0 ]; then
        logger -p daemon.err "$script returned non-zero exit status $exit_status"
    fi

    return $exit_status
}

# run scripts in given directory
run_hookdir() {
    local dir="$1"
    local exit_status=0

    if [ -d "$dir" ]; then
        for script in $(run-parts --list $dir); do
            run_hook $script
            exit_status=$((exit_status|$?))
        done
    fi

    return $exit_status
}

# Must be used on exit.   Invokes the local dhcp client exit hooks, if any.
exit_with_hooks() {
    local exit_status=$1

    # Source the documented exit-hook script, if it exists
    if ! run_hook /etc/dhcp/dhclient-exit-hooks; then
        exit_status=$?
    fi

    # Now run scripts in the Debian-specific directory.
    if ! run_hookdir /etc/dhcp/dhclient-exit-hooks.d; then
        exit_status=$?
    fi

    exit $exit_status
}


# The 576 MTU is only used for X.25 and dialup connections
# where the admin wants low latency.  Such a low MTU can cause
# problems with UDP traffic, among other things.  As such,
# disallow MTUs from 576 and below by default, so that broken
# MTUs are ignored, but higher stuff is allowed (1492, 1500, etc).
if [ -z "$new_interface_mtu" ] || [ "$new_interface_mtu" -le 576 ]; then
    new_interface_mtu=''
fi


# The action starts here

# Invoke the local dhcp client enter hooks, if they exist.
run_hook /etc/dhcp/dhclient-enter-hooks
run_hookdir /etc/dhcp/dhclient-enter-hooks.d

# Execute the operation
case "$reason" in

    ### DHCPv4 Handlers

    MEDIUM|ARPCHECK|ARPSEND)
        # Do nothing
        ;;
    PREINIT)
        # The DHCP client is requesting that an interface be
        # configured as required in order to send packets prior to
        # receiving an actual address. - dhclient-script(8)

        # ensure interface is up
        ip link set dev ${interface} up

        if [ -n "$alias_ip_address" ]; then
            # flush alias IP from interface
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        ;;

    BOUND|RENEW|REBIND|REBOOT)
        set_hostname

        if [ -n "$old_ip_address" ] && [ -n "$alias_ip_address" ] &&
           [ "$alias_ip_address" != "$old_ip_address" ]; then
            # alias IP may have changed => flush it
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        if [ -n "$old_ip_address" ] &&
           [ "$old_ip_address" != "$new_ip_address" ]; then
            # leased IP has changed => flush it
            ip -4 addr flush dev ${interface} label ${interface}
        fi

        if [ -z "$old_ip_address" ] ||
           [ "$old_ip_address" != "$new_ip_address" ] ||
           [ "$reason" = "BOUND" ] || [ "$reason" = "REBOOT" ]; then
            # new IP has been leased or leased IP changed => set it
            ip -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \
                ${new_broadcast_address:+broadcast $new_broadcast_address} \
                dev ${interface} label ${interface}

            if [ -n "$new_interface_mtu" ]; then
                # set MTU
                ip link set dev ${interface} mtu ${new_interface_mtu}
            fi

    # if we have $new_rfc3442_classless_static_routes then we have to
    # ignore $new_routers entirely
    if [ ! "$new_rfc3442_classless_static_routes" ]; then
    # set if_metric if IF_METRIC is set or there's more than one router
    if_metric="$IF_METRIC"
    if [ "${new_routers%% *}" != "${new_routers}" ]; then
if_metric=${if_metric:-1}
    fi

    for router in $new_routers; do
if [ "$new_subnet_mask" = "255.255.255.255" ]; then
    # point-to-point connection => set explicit route
    ip -4 route add ${router} dev $interface >/dev/null 2>&1
fi

# set default route
ip -4 route add default via ${router} dev ${interface} \
    ${if_metric:+metric $if_metric} >/dev/null 2>&1

if [ -n "$if_metric" ]; then
    if_metric=$((if_metric+1))
fi
    done
    fi
        fi

        if [ -n "$alias_ip_address" ] &&
           [ "$new_ip_address" != "$alias_ip_address" ]; then
            # separate alias IP given, which may have changed
            # => flush it, set it & add host route to it
            ip -4 addr flush dev ${interface} label ${interface}:0
            ip -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \
                dev ${interface} label ${interface}:0
            ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
        fi

        # update /etc/resolv.conf
        make_resolv_conf

        ;;

    EXPIRE|FAIL|RELEASE|STOP)
        if [ -n "$alias_ip_address" ]; then
            # flush alias IP
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        if [ -n "$old_ip_address" ]; then
            # flush leased IP
            ip -4 addr flush dev ${interface} label ${interface}
        fi

        if [ -n "$alias_ip_address" ]; then
            # alias IP given => set it & add host route to it
            ip -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \
                dev ${interface} label ${interface}:0
            ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
        fi

        ;;

    TIMEOUT)
        if [ -n "$alias_ip_address" ]; then
            # flush alias IP
            ip -4 addr flush dev ${interface} label ${interface}:0
        fi

        # set IP from recorded lease
        ip -4 addr add ${new_ip_address}${new_subnet_mask:+/$new_subnet_mask} \
            ${new_broadcast_address:+broadcast $new_broadcast_address} \
            dev ${interface} label ${interface}

        if [ -n "$new_interface_mtu" ]; then
            # set MTU
            ip link set dev ${interface} mtu ${new_interface_mtu}
        fi

        # if there is no router recorded in the lease or the 1st router answers pings
        if [ -z "$new_routers" ] || ping -q -c 1 "${new_routers%% *}"; then
    # if we have $new_rfc3442_classless_static_routes then we have to
    # ignore $new_routers entirely
    if [ ! "$new_rfc3442_classless_static_routes" ]; then
    if [ -n "$alias_ip_address" ] &&
       [ "$new_ip_address" != "$alias_ip_address" ]; then
# separate alias IP given => set up the alias IP & add host route to it
ip -4 addr add ${alias_ip_address}${alias_subnet_mask:+/$alias_subnet_mask} \
    dev ${interface} label ${interface}:0
ip -4 route add ${alias_ip_address} dev ${interface} >/dev/null 2>&1
    fi

    # set if_metric if IF_METRIC is set or there's more than one router
    if_metric="$IF_METRIC"
    if [ "${new_routers%% *}" != "${new_routers}" ]; then
if_metric=${if_metric:-1}
    fi

    # set default route
    for router in $new_routers; do
ip -4 route add default via ${router} dev ${interface} \
    ${if_metric:+metric $if_metric} >/dev/null 2>&1

if [ -n "$if_metric" ]; then
    if_metric=$((if_metric+1))
fi
    done
    fi

            # update /etc/resolv.conf
            make_resolv_conf
        else
            # flush all IPs from interface
            ip -4 addr flush dev ${interface}
            exit_with_hooks 2
        fi

        ;;

    ### DHCPv6 Handlers
    # TODO handle prefix change: ?based on ${old_ip6_prefix} and ${new_ip6_prefix}?

    PREINIT6)
        # ensure interface is up
        ip link set ${interface} up

        # flush any stale global permanent IPs from interface
        ip -6 addr flush dev ${interface} scope global permanent

        ;;

    BOUND6|RENEW6|REBIND6)
        if [ "${new_ip6_address}" ]; then
            # set leased IP
            ip -6 addr add ${new_ip6_address} \
                dev ${interface} scope global
        fi

        # update /etc/resolv.conf
        if [ "${reason}" = BOUND6 ] ||
           [ "${new_dhcp6_name_servers}" != "${old_dhcp6_name_servers}" ] ||
           [ "${new_dhcp6_domain_search}" != "${old_dhcp6_domain_search}" ]; then
            make_resolv_conf
        fi

        ;;

    DEPREF6)
        # set preferred lifetime of leased IP to 0
        ip -6 addr change ${cur_ip6_address} \
            dev ${interface} scope global preferred_lft 0

        ;;

    EXPIRE6|RELEASE6|STOP6)
        if [ -z "${old_ip6_address}" ]; then
            exit_with_hooks 2
        fi

        # delete leased IP
        ip -6 addr del ${old_ip6_address} \
            dev ${interface}

        ;;
esac

exit_with_hooks 0
--- End code ---

c) This part is easy:

--- Code: ---sudo mkdir /var/db

--- End code ---

Make sure dhclient will have everything it needs next boot! Add these lines to /opt/.filetool.lst:

--- Code: ---etc/dhcp/dhclient.conf
sbin/dhclient-script
var/db/
--- End code ---

And do a backup: filetool.sh -b

Now reboot and connect using the new approach. Here is the key part of my "autowifi" script (which runs with root privileges):


--- Code: ---ssid=WorkplaceOpen
iface=wlan0
auth_file=/tmp/wifi.conf

modprobe ipv6
printf 'network={\n\tssid="%s"\n\tkey_mgmt=NONE\n}\n' $ssid > $auth_file
wpa_supplicant -i $iface -c $auth_file &
sleep 3
dhclient -v -cf /etc/dhcp/dhclient.conf $iface
--- End code ---

I'm happy to say that using the new approach (IPv6 enabled + wpa_supplicant + dhclient) I no longer have experienced any dropped connections.

I hope this is helpful to someone.

    [EDIT]: Fixed  several  typos.  Rich

Rich:
Hi GNUser

--- Quote from: GNUser on November 25, 2019, 12:35:23 PM ---Backup command should have been filetool.sh -b, obviously. Sorry for the typo.
--- End quote ---
Fixed.

GNUser:
Thanks :)

GNUser:
In old version of my autowifi script there should be a sleep command (I use sleep 3) between iwconfig and udhcpc commands. In new version, sleep (again, I use sleep 3) between wpa_supplicant and dhclient commands. Gosh, sorry for the oversight.

P.S. I wish I could edit my own posts later. Why is there only a brief window of time in which a forum user can edit his own post?

Rich:
Hi GNUser
Fixed.

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