From 30656b097e9dd7978d3fe9416cb9f5a421a9e63e Mon Sep 17 00:00:00 2001 From: Zhang Chen Date: Tue, 27 Sep 2016 10:22:34 +0800 Subject: filter-rewriter: rewrite tcp packet to keep secondary connection We will rewrite tcp packet secondary received and sent. When colo guest is a tcp server. Firstly, client start a tcp handshake. the packet's seq=client_seq, ack=0,flag=SYN. COLO primary guest get this pkt and mirror(filter-mirror) to secondary guest, secondary get it use filter-redirector. Then,primary guest response pkt (seq=primary_seq,ack=client_seq+1,flag=ACK|SYN). secondary guest response pkt (seq=secondary_seq,ack=client_seq+1,flag=ACK|SYN). In here,we use filter-rewriter save the secondary_seq to it's tcp connection. Finally handshake,client send pkt (seq=client_seq+1,ack=primary_seq+1,flag=ACK). Here,filter-rewriter can get primary_seq, and rewrite ack from primary_seq+1 to secondary_seq+1, recalculate checksum. So the secondary tcp connection kept good. When we send/recv packet. client send pkt(seq=client_seq+1+data_len,ack=primary_seq+1,flag=ACK|PSH). filter-rewriter rewrite ack and send to secondary guest. primary guest response pkt (seq=primary_seq+1,ack=client_seq+1+data_len,flag=ACK) secondary guest response pkt (seq=secondary_seq+1,ack=client_seq+1+data_len,flag=ACK) we rewrite secondary guest seq from secondary_seq+1 to primary_seq+1. So tcp connection kept good. In code We use offset( = secondary_seq - primary_seq ) to rewrite seq or ack. handle_primary_tcp_pkt: tcp_pkt->th_ack += offset; handle_secondary_tcp_pkt: tcp_pkt->th_seq -= offset; Signed-off-by: Zhang Chen Signed-off-by: Li Zhijian Signed-off-by: Wen Congyang Signed-off-by: Jason Wang --- net/colo.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'net/colo.c') diff --git a/net/colo.c b/net/colo.c index 124994c99f..6a6eacd2dc 100644 --- a/net/colo.c +++ b/net/colo.c @@ -134,6 +134,8 @@ Connection *connection_new(ConnectionKey *key) conn->ip_proto = key->ip_proto; conn->processing = false; + conn->offset = 0; + conn->syn_flag = 0; g_queue_init(&conn->primary_list); g_queue_init(&conn->secondary_list); -- cgit 1.4.1