Get local network interface addresses using only proc?
My solution to retrieve IPv4 network config, using /proc only:
Unfortunately, this is bash (bash only and without any fork), not python. But I hope this will be readable:
#!/bin/bash
# ip functions that set variables instead of returning to STDOUT
hexToInt() {
printf -v $1 "%d\n" 0x${2:6:2}${2:4:2}${2:2:2}${2:0:2}
}
intToIp() {
local var=$1 iIp
shift
for iIp ;do
printf -v $var "%s %s.%s.%s.%s" "${!var}" $(($iIp>>24)) \
$(($iIp>>16&255)) $(($iIp>>8&255)) $(($iIp&255))
done
}
maskLen() {
local i
for ((i=0; i<32 && ( 1 & $2 >> (31-i) ) ;i++));do :;done
printf -v $1 "%d" $i
}
# The main loop.
while read -a rtLine ;do
if [ ${rtLine[2]} == "00000000" ] && [ ${rtLine[7]} != "00000000" ] ;then
hexToInt netInt ${rtLine[1]}
hexToInt maskInt ${rtLine[7]}
if [ $((netInt&maskInt)) == $netInt ] ;then
for procConnList in /proc/net/{tcp,udp} ;do
while IFS=': \t\n' read -a conLine ;do
if [[ ${conLine[1]} =~ ^[0-9a-fA-F]*$ ]] ;then
hexToInt ipInt ${conLine[1]}
[ $((ipInt&maskInt)) == $netInt ] && break 3
fi
done < $procConnList
done
fi
fi
done < /proc/net/route
# And finaly the printout of what's found
maskLen maskBits $maskInt
intToIp addrLine $ipInt $netInt $maskInt
printf -v outForm '%-12s: %%s\\n' Interface Address Network Netmask Masklen
printf "$outForm" $rtLine $addrLine $maskBits\ bits
There is a sample of output:
Interface : eth0
Address : 192.168.1.32
Network : 192.168.1.0
Netmask : 255.255.255.0
Masklen : 24 bits
Explanation:
I use integer value of IPV4 in order to check IP & MASK == NETWORK.
I read first /proc/net/route to find routing configurations, searching for routes reachable without any gateway (gw==000000).
For such a route, I search in all connections (TCP, than UDP if not found in TCP) for connection using this route, the first end point is my host address.
Nota: This won't work with PPP connections
Nota2: This won't work on a totally quiet host without any opened network connection.
You could do something like echo -ne '' | nc -q 0 -w 1 8.8.8.8 80 & sleep .2 && ./retrieveIp.sh for ensuring that something where found in /proc/net/tcp.
Nota3, 2016-09.23: New bash version use >(command) syntax for multiple inline pipe feature. This implie a bug at line 18: a space must be present between > and ( !!
New version with gateway
There is a little patch: Once you create a file called getIPv4.sh by copying previous script, you could paste the following to the command: patch -p0
--- getIPv4.sh
+++ getIPv4.sh
@@ -35,13 +35,16 @@
done < $procConnList
done
fi
+ elif [ ${rtLine[1]} == "00000000" ] && [ ${rtLine[7]} == "00000000" ] ;then
+ hexToInt netGw ${rtLine[2]}
fi
done < /proc/net/route
# And finaly the printout of what's found
maskLen maskBits $maskInt
-intToIp addrLine $ipInt $netInt $maskInt
-printf -v outForm '%-12s: %%s\\n' Interface Address Network Netmask Masklen
+intToIp addrLine $ipInt $netInt $netGw $maskInt
+printf -v outForm '%-12s: %%s\\n' \
+ Interface Address Network Gateway Netmask Masklen
printf "$outForm" $rtLine $addrLine $maskBits\ bits
End with Ctrld, this may output:
patching file getIPv4.sh
And maybe
Hunk #1 succeeded at 35 with fuzz 2.
Then re-run your script:
getIPv4.sh
Interface : eth0
Address : 192.168.1.32
Network : 192.168.1.0
Gateway : 192.168.1.1
Netmask : 255.255.255.0
Masklen : 24 bits
You may find the output of ip addr show easier to parse than output from other tools:
$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:24:1d:ce:47:05 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.121/24 brd 192.168.0.255 scope global eth0
inet6 fe80::224:1dff:fece:4705/64 scope link
valid_lft forever preferred_lft forever
3: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000
link/ether 00:24:1d:ce:35:d5 brd ff:ff:ff:ff:ff:ff
4: virbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN
link/ether 92:e3:6c:08:1f:af brd ff:ff:ff:ff:ff:ff
inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
inet6 fe80::90e3:6cff:fe08:1faf/64 scope link
valid_lft forever preferred_lft forever
Another option is the file /proc/net/tcp. It shows all currently-open TCP sessions, which is different than what you asked for, but might be Good Enough.
$ cat tcp
sl local_address rem_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode
0: 00000000:0050 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 13536 1 ffff88019f0a1380 300 0 0 2 -1
1: 00000000:1355 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 19877854 1 ffff880016e69380 300 0 0 2 -1
2: 017AA8C0:0035 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 13633 1 ffff88019f0a1a00 300 0 0 2 -1
3: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 8971 1 ffff88019f0a0000 300 0 0 2 -1
4: 0100007F:0277 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 12952880 1 ffff880030e30680 300 0 0 2 -1
5: 00000000:0539 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 14332 1 ffff88019f0a2080 300 0 0 2 -1
6: 00000000:C000 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 14334 1 ffff88019f0a2700 300 0 0 2 -1
7: 0100007F:0A44 00000000:0000 0A 00000000:00000000 00:00000000 00000000 119 0 51794804 1 ffff880016e6a700 300 0 0 2 -1
8: 7900A8C0:B094 53D50E48:01BB 01 00000000:00000000 00:00000000 00000000 1000 0 64877487 1 ffff880100502080 23 4 16 4 -1
9: 7900A8C0:9576 537F7D4A:01BB 06 00000000:00000000 03:00000E5D 00000000 0 0 0 3 ffff880100c84600
10: 7900A8C0:CC84 0CC181AE:01BB 01 00000000:00000000 00:00000000 00000000 1000 0 61775908 1 ffff880198715480 35 4 11 4 -1
$ irb
irb(main):001:0> [0x79, 0x00, 0xa8, 0xc0]
=> [121, 0, 168, 192]
My IP is 192.168.0.121; note the funny arithmetic to make it come out right. :)
/proc/net/fib_trie holds the network topography
To simply print the addresses of all adapters:
$ awk '/32 host/ { print f } {f=$2}' <<< "$(</proc/net/fib_trie)"
127.0.0.1
192.168.0.5
192.168.1.14
To determine the adapter of those addresses (a) consult the adapters' destination networks from /proc/net/route, (b) match those networks with the ones of /proc/net/fib_trie and (c) print the corresponding /32 host addresses listed under those networks.
Again no python unfortunately, but a quite awky bash approach:
#!/bin/bash
ft_local=$(awk '$1=="Local:" {flag=1} flag' <<< "$(</proc/net/fib_trie)")
for IF in $(ls /sys/class/net/); do
networks=$(awk '$1=="'$IF'" && $3=="00000000" && $8!="FFFFFFFF" {printf $2 $8 "\n"}' <<< "$(</proc/net/route)" )
for net_hex in $networks; do
net_dec=$(awk '{gsub(/../, "0x& "); printf "%d.%d.%d.%d\n", $4, $3, $2, $1}' <<< $net_hex)
mask_dec=$(awk '{gsub(/../, "0x& "); printf "%d.%d.%d.%d\n", $8, $7, $6, $5}' <<< $net_hex)
awk '/'$net_dec'/{flag=1} /32 host/{flag=0} flag {a=$2} END {print "'$IF':\t" a "\n\t'$mask_dec'\n"}' <<< "$ft_local"
done
done
exit 0
output:
eth0: 192.168.0.5
255.255.255.0
lo: 127.0.0.1
255.0.0.0
wlan0: 192.168.1.14
255.255.255.0
Known limitation:
This approach does not work reliably for host addresses that share the network with other host addresses. This loss of network uniqueness makes it impossible to determine the correct host address from fib_trie as the order of those addresses does not necessarily match the order of networks of route.
Having said that, I'm not sure why you would want multiple host addresses belonging to the same network in first place. So in most use cases this approach should work just fine.
There is no IPv4 analog of /proc/net/if_inet6
ifconfig does:
fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP)
ioctl(fd, SIOCGIFCONF, ...)
You'll get something like this:
ioctl(4, SIOCGIFCONF, {120, {{"lo", {AF_INET, inet_addr("127.0.0.1")}}, {"eth0", {AF_INET, inet_addr("10.6.23.69")}}, {"tun0", {AF_INET, inet_addr("10.253.10.151")}}}})