ipvs: drop first packet to redirect conntrack
Jiri Bohac is reporting for a problem where the attempt to reschedule existing connection to another real server needs proper redirect for the conntrack used by the IPVS connection. For example, when IPVS connection is created to NAT-ed real server we alter the reply direction of conntrack. If we later decide to select different real server we can not alter again the conntrack. And if we expire the old connection, the new connection is left without conntrack. So, the only way to redirect both the IPVS connection and the Netfilter's conntrack is to drop the SYN packet that hits existing connection, to wait for the next jiffie to expire the old connection and its conntrack and to rely on client's retransmission to create new connection as usually. Jiri Bohac provided a fix that drops all SYNs on rescheduling, I extended his patch to do such drops only for connections that use conntrack. Here is the original report from Jiri Bohac: Since commit dc7b3eb9 ("ipvs: Fix reuse connection if real server is dead"), new connections to dead servers are redistributed immediately to new servers. The old connection is expired using ip_vs_conn_expire_now() which sets the connection timer to expire immediately. However, before the timer callback, ip_vs_conn_expire(), is run to clean the connection's conntrack entry, the new redistributed connection may already be established and its conntrack removed instead. Fix this by dropping the first packet of the new connection instead, like we do when the destination server is not available. The timer will have deleted the old conntrack entry long before the first packet of the new connection is retransmitted. Fixes: dc7b3eb9 ("ipvs: Fix reuse connection if real server is dead") Signed-off-by: NJiri Bohac <jbohac@suse.cz> Signed-off-by: NJulian Anastasov <ja@ssi.bg> Signed-off-by: NSimon Horman <horms@verge.net.au>
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