On Tuesday 15 April 2008 08:16:58 Julian Anastasov wrote: > On Mon, 14 Apr 2008, Jason Stubbs wrote: > > > > * IP_VS_CONN_F_BYPASS - what is this? > > > > > > IP_VS_CONN_F_BYPASS is used for transparent proxy setups when > > > real server (cache server) is not present and we should forward the > > > traffic to original destination. The idea is request still to be > > > served. In such case IPVS traffic uses the original destination instead > > > of real server. > > > > Not tested yet. I assume I just need to add a real server with the same > > IP/port as the virtual server? > > Not sure, may be IP:PORT of LVS's uplink gateway. In such > setups clients are usually internal hosts using LVS box as gateway. I figured this one out by looking at the source and it tested fine too. The virtual server must be fwmark and the sysctl ip.vs.cache_bypass must be set to 1. With those settings, the packet is passed when there are no real servers available rather than being rejected with ICMP_PORT_UNREACH. > > > - Netfilter can re-route sometimes (eg. after mangle), it can cause > > > properly routed LVS-DR traffic to fail. > > > > I don't understand exactly what you mean by this. It could only happen if > > the user sets rules that causes it to happen right? > > May be the things have changed, not sure. The problem is when > functions like ip_route_me_harder() are called for packets that > are already forwarded by IPVS (skb has attached route for the > real server). In such case skb still shows VIP as iph->daddr and > a rerouting can result in local route. But latest kernels may be > reroute only in LOCAL_OUT, so this is not a problem. > As for the double POST_ROUTING log entries ... I'm checking > this NF_HOOK_THRESH call with NF_IP_PRI_LAST. For me, it looks like > net/netfilter/core.c:nf_iterate() calls only handlers when > elem->priority >= hook_thresh. But you put ip_vs_in() at the same > priority NF_IP_PRI_LAST. May be ip_vs_in() is called twice? The dst_output specified to NF_HOOK_THRESH is called after nf_iterate() is finished. dst_output then calls NF_HOOK_THRESH with POST_ROUTING again passing the result to an internal function to actually send the packet out. There's no way around it except perhaps with an NF_STOP hook. I'd like to figure out how traffic (congestion) control fits in first though. > Also, if ip_vs_in() is called after SNAT I'm curious, isn't > ip_vs_ftp working with DNAT-ed skb (if you have netfilter ftp nat > module) ? May be things don't break because IPVS is careful not to > damage packets it can not recognize. But do we work properly with > the FTP commands in ip_vs_ftp_in(), do we create properly FTP data > connections in IPVS? I assume you test both passive and active FTP. > If the goal is -m state to work correctly, are you sure the IPVS FTP > data connections work correctly (as RELATED traffic)? I tried again with the accept rule as: iptables -t filter -A FORWARD -p tcp -d 192.168.0.7 --dport 21 -i eth0 -j ACCEPT However, it still worked fine in both passive and active modes. The patch series I posted may make it clear, but the way I visualize what's happening is that there are two proxies between the client and the server. Something like: client => DNAT => LVS => server. DNAT and LVS are unaware of each other's existence, but there is no problems because the order of processing make it transparent. -- Jason Stubbs <j.stubbs@xxxxxxxxxxxxxxx> LINKTHINK INC. 東京都渋谷区桜ヶ丘町22-14 N.E.S S棟 3F TEL 03-5728-4772 FAX 03-5728-4773 -- To unsubscribe from this list: send the line "unsubscribe lvs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
