linux-kernel - Re: some trouble when using vrf

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Date:   Tue, 16 Apr 2019 22:16:22 +0800
From:   linmiaohe <linmiaohe@...wei.com>
To:     <mmanning@...tta.att-mail.com>,
        David Ahern <dsa@...ulusnetworks.com>, <shrijeet@...il.com>,
        <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Mingfangsen <mingfangsen@...wei.com>
Subject: Re: some trouble when using vrf



On 2019/4/16 20:11, Mike Manning wrote:
> On 16/04/2019 12:26, linmiaohe wrote:
>> Hi all:
>>     I meet some trouble when using vrf, it's very nice of you if you
>> can help me fix it.
>>
>>     1.If I bind a vrf address before I set SO_BINDTODEVICE opts to bind an
>> enslaved device, "Cannot assign requested address" will occurs. It's
>> because only after we set SO_BINDTODEVICE opts to bind an enslaved device,
>> then we can lookup the route in the specified l3mdev domain.
>>     I think we couldn't limit the order of bind ip addr and SO_BINDTODEVICE opts
>> otherwise many vrf unaware apps many need to change their code.
>>     I can't find a convenient way to fix it.Here is an example:
>>
>>     ...
>>     bind(sock_fd, (struct sockaddr *)&addr_serv, sizeof(addr_serv));
>>     ...
>>     ret = setsockopt(sock_fd, SOL_SOCKET, SO_BINDTODEVICE, bind_dev, strlen(bind_dev)+1);
>>     ...
>>     This code snipet doesn't work if the ip address of addr_serv is not in default vrf. And
>> "Cannot assign requested address" will occurs.
> Or you can run instances of vrf-unaware applications per VRF with 'sudo
> ip vrf exec <vrf> <cmd>', with the 3 sysctl you indicate below set to 0.
>>     2.When I run a udp server in default vrf and set net.ipv4.udp_l3mdev_accept=1,
>> it's supposed to work accorss VRFs.
>>     But it occurs when udp server received a packet, it sends back with the source
>> ip address from default vrf which is supposed to from the specified l3mdev domain.
>> And the connection between server and client is broken. It's because udp server
>> run in default vrf and doesn't bind the enslaved device, so only the route table in
>> default vrf is avaliable.
>>
>>     For example,I run a udp server in default vrf and set net.ipv4.udp_l3mdev_accept=1:
>>     [root@...alhost vrf]# sysctl -a | grep l3mdev
>>     net.ipv4.raw_l3mdev_accept = 1
>>     net.ipv4.tcp_l3mdev_accept = 1
>>     net.ipv4.udp_l3mdev_accept = 1
>>
>>     Then connect the server and send a udp packet to the specified vrf. Here is tcpdump output:
>>     17:28:54.925417 IP 10.0.0.2.43003 > 10.0.0.1.irdmi: UDP, length 17
>>     17:28:54.925953 IP 9.85.153.236.irdmi > 10.0.0.2.43003: UDP, length 17
>>     ps. 10.0.0.2 is client ip, 10.0.0.1 is specified vrf ip, and 9.85.153.236 is default vrf ip.
>>     10.0.0.1 and 9.85.153.236 are in the same host.
>>
>> Thanks a lot if you can help me fix these. Have a nice day.
>>
>>
>>
> 
> 
> .
> 
    Thanks for your reply. Run instances of vrf-unaware applications per VRF is an optional solution for problem 1.
But maybe it will limits the applications supposed to accross VRFS can't coexist with per VRF applications as
udp_l3mdev_accept is globally effective.
    And what about problem 2?
    Thanks again.