Dotaz: jak vypsat aktualni routovani

[marek]

Dobry den. Narazil jsem na zajimavou vyzvu.

Uvod: Mam sit s ne uplne standartnim routovanim. V rozsahu 172.16.0.0/16 maji vsichni default gw 172.16.0.1. Sit 172.26.100.0/24 je vsak pripojena do routeru 172.16.20.20. Tato routa je na stroji s 172.16.0.1 nastavena. Pokud zahajim komunikaci z 172.16.0.2 na 172.26.100.0/24, tak prvni packety jdou na 172.16.0.1. Stroj s 172.16.0.1 je preposle na 172.16.20.20 a zaroven vysle icmp type 5 code 0 (Redirect datagrams for the Network) na 172.16.0.2,aby to priste poslal primo. Ten to skutecne priste posle primo a 172.16.0.1 ma pokoj. Vse bezi na linuxu. Vse funguje k naproste spokojenosti.

Vlastni dotaz: Jak vypisu podle kterych pravidel se aktualne routuje (i podle Service type), jak do tech pravidel mohu zasahnout, jak ovlivnim co presne za code posle 172.16.0.1.

Marek

Odpovědi

[Michal Kubeček]

Pokud chcete opravdu kompletní, tak 'ip rule show' a pak pro jednotlivé tabulky 'ip route show table n'.

[marek]

Dobry den.

Dekuji za reakci.

To bylo to prvni, co jsem zkousel, ale: for ((i=0;i<256;i++)); do ip route show table $i; done | grep 172.26.100 nevypise i v okamziku, kdy soubezne:

marek@setapouch:~$ ping 172.26.100.1
PING 172.26.100.1 (172.26.100.1) 56(84) bytes of data.
64 bytes from 172.26.100.1: icmp_seq=1 ttl=255 time=2.63 ms
From 172.16.0.1: icmp_seq=2 Redirect Host(New nexthop: 172.16.20.20)
64 bytes from 172.26.100.1: icmp_seq=2 ttl=255 time=1.88 ms
From 172.16.0.1: icmp_seq=3 Redirect Host(New nexthop: 172.16.20.20)
64 bytes from 172.26.100.1: icmp_seq=3 ttl=255 time=2.08 ms
64 bytes from 172.26.100.1: icmp_seq=4 ttl=255 time=1.84 m

vubec nic.

Marek

[Michal Kubeček]

Trochu jsem se ztratil v tom, v čem je problém. V tom, že váš stroj redirecty ignoruje, nebo v tom, že je akceptuje, ale neprojeví se to ve směrovacích tabulkách?

[marek]

Problem je v tom, ze ip nic nevypise, ackoli redirecty se akceptuji:

tcpdump -nne host 172.26.100.1
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
12:29:29.153003 00:1c:c0:07:06:64 > 00:20:9c:6b:56:cb, ethertype IPv4 (0x0800), length 98: 172.16.200.100 > 172.26.100.1: ICMP echo request, id 21787, seq 135, length 64
12:29:29.179324 00:20:9c:6b:56:cb > 00:1c:c0:07:06:64, ethertype IPv4 (0x0800), length 98: 172.26.100.1 > 172.16.200.100: ICMP echo reply, id 21787, seq 135, length 64


arp -n 172.16.20.20
Address                  HWtype  HWaddress           Flags Mask            Iface
172.16.20.20             ether   00:20:9c:6b:56:cb   C                     eth0

Marek

[marek]

Takze vypsat to uz umim:

POROVNATEL="eth0.([0-9ABCDEF]{2})([0-9ABCDEF]{2})([0-9ABCDEF]{2})([0-9ABCDEF]{2}).([0-9ABCDEF]{2})([0-9ABCDEF]{2})([0-9ABCDEF]{2})([0-9ABCDEF]{2}).*"
while read IP ;do [[ $IP =~ $POROVNATEL ]] && echo -e "ibase=16\n ${BASH_REMATCH[4]}\n${BASH_REMATCH[3]}\n${BASH_REMATCH[2]}\n${BASH_REMATCH[1]}\n" |bc| tr "\n" "."&&\
> echo -en "\t"&&echo -e "ibase=16\n ${BASH_REMATCH[8]}\n${BASH_REMATCH[7]}\n${BASH_REMATCH[6]}\n${BASH_REMATCH[5]}\n" |bc| tr "\n" "." && echo;  done </proc/net/rt_cache
172.26.100.1.   172.16.20.20.
172.16.1.20.    172.16.1.20.
74.125.87.138.  172.16.0.1.
74.125.87.138.  172.16.0.1.
195.70.150.7.   172.16.0.1.
172.26.100.1.   172.16.20.20.
77.78.99.22.    172.16.0.1.
172.16.1.27.    172.16.1.27.
74.125.87.100.  172.16.0.1.
74.125.87.102.  172.16.0.1.
77.78.99.23.    172.16.0.1.
172.16.1.20.    172.16.1.20.
62.168.44.116.  172.16.0.1.
74.125.87.101.  172.16.0.1.
62.168.44.117.  172.16.0.1.
172.16.0.2.     172.16.0.2.
86.49.105.86.   172.16.0.1.
74.125.87.102.  172.16.0.1.
77.78.99.21.    172.16.0.1.
77.78.99.26.    172.16.0.1.
195.70.150.7.   172.16.0.1.
77.78.99.21.    172.16.0.1.
74.125.87.113.  172.16.0.1.
62.168.44.116.  172.16.0.1.
74.125.87.100.  172.16.0.1.
172.16.0.2.     172.16.0.2.
62.168.44.115.  172.16.0.1.
77.78.99.22.    172.16.0.1.
62.168.44.117.  172.16.0.1.
172.16.1.27.    172.16.1.27.

Ted to jeste zacit ovladat:

echo 0 > /proc/sys/net/ipv4/conf/eth0/accept_redirects

zda se nefunguje

Marek

[petr_p]

ip route show cache :)

[marek]

Dekuji, minimalne polovinu dotazu to resi:

ip route flush table cache

funguje,

ale treba:

ip route del 172.26.100.1 via 172.16.20.20 dev eth0  src 172.16.200.100  table cache
Error: argument "cache" is wrong: "table" value is invalid

Marek