so, setting fl.nl_u.ip4_u.saddr = 0 is a kind of "jolly" selector of the source address? On Fri, Sep 17, 2010 at 11:08 AM, Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote: > Le vendredi 17 septembre 2010 à 10:46 +0200, Nicola Padovano a écrit : >> Aijaz, great! Now it' clear. Thank you. >> It remains a problem: the meaning of >> >> fl.nl_u.ip4_u.saddr = 0 >> >> But, first of all: >> - we know that a routing table doesn't contain the ip source >> - but the routing cache contains it. >> >> so my first question is: why routing cache has it and routing cache >> not? what it its usage? >> Then my second question: the meaning of fl.nl_u.ip4_u.saddr = 0 >> >> thank you very much > > # ip addr show dev eth1 > 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP > qlen 1000 txqueues 4 > link/ether f4:ce:46:bb:32:d4 brd ff:ff:ff:ff:ff:ff > inet 192.168.20.108/24 brd 192.168.20.255 scope global eth1 > inet6 fe80::f6ce:46ff:febb:32d4/64 scope link > valid_lft forever preferred_lft forever > # ip addr add 192.168.20.67/24 dev eth1 > # ip addr show dev eth1 > 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP > qlen 1000 txqueues 4 > link/ether f4:ce:46:bb:32:d4 brd ff:ff:ff:ff:ff:ff > inet 192.168.20.108/24 brd 192.168.20.255 scope global eth1 > inet 192.168.20.67/24 scope global secondary eth1 > inet6 fe80::f6ce:46ff:febb:32d4/64 scope link > valid_lft forever preferred_lft forever > # ip ro > 192.168.20.0/24 dev eth1 proto kernel scope link src 192.168.20.108 > default via 192.168.20.254 dev eth1 > > # ip ro flush cache > # ip ro flush cache > # ip ro get 192.168.20.110 > 192.168.20.110 dev eth1 src 192.168.20.108 > cache mtu 1500 advmss 1460 hoplimit 64 > # ip ro get 192.168.20.110 from 192.168.20.67 > 192.168.20.110 from 192.168.20.67 dev eth1 > cache mtu 1500 advmss 1460 hoplimit 64 > # ip ro list cache > 192.168.20.110 dev eth1 src 192.168.20.108 > cache mtu 1500 advmss 1460 hoplimit 64 > 192.168.20.110 from 192.168.20.67 dev eth1 > cache mtu 1500 advmss 1460 hoplimit 64 > > You can see two different routes in cache to reach 192.168.20.110, > one from "0.0.0.0" (we force src 192.168.20.108), > one from 192.168.20.67 > > With different keys (src addr, tos, fwmark, ...) we can have a lot of > different routes for apparently same destination > > > -- Nicola Padovano e-mail: nicola.padovano@xxxxxxxxx web: http://npadovano.altervista.org -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
