On 06/24/2016 02:08 PM, Jason Wang wrote:
On 2016年06月23日 18:48, Zhang Chen wrote:
On 06/22/2016 02:34 PM, Jason Wang wrote:
On 2016年06月22日 11:12, Zhang Chen wrote:
On 06/20/2016 08:14 PM, Dr. David Alan Gilbert wrote:
* Jason Wang (jasow...@redhat.com) wrote:
On 2016年06月14日 19:15, Zhang Chen wrote:
We will rewrite tcp packet secondary received and sent.
More verbose please. E.g which fields were rewrote and why.
OK.
Signed-off-by: Zhang Chen <zhangchen.f...@cn.fujitsu.com>
Signed-off-by: Li Zhijian <lizhij...@cn.fujitsu.com>
Signed-off-by: Wen Congyang <we...@cn.fujitsu.com>
---
net/filter-rewriter.c | 94
+++++++++++++++++++++++++++++++++++++++++++++++++--
trace-events | 3 ++
2 files changed, 95 insertions(+), 2 deletions(-)
diff --git a/net/filter-rewriter.c b/net/filter-rewriter.c
index 12f88c5..86a2f53 100644
--- a/net/filter-rewriter.c
+++ b/net/filter-rewriter.c
@@ -21,6 +21,7 @@
#include "qemu/main-loop.h"
#include "qemu/iov.h"
#include "net/checksum.h"
+#include "trace.h"
#define FILTER_COLO_REWRITER(obj) \
OBJECT_CHECK(RewriterState, (obj), TYPE_FILTER_REWRITER)
@@ -64,6 +65,75 @@ static int is_tcp_packet(Packet *pkt)
}
}
+static int handle_primary_tcp_pkt(NetFilterState *nf,
+ Connection *conn,
+ Packet *pkt)
+{
+ struct tcphdr *tcp_pkt;
+
+ tcp_pkt = (struct tcphdr *)pkt->transport_layer;
+
+ if (trace_event_get_state(TRACE_COLO_FILTER_REWRITER_DEBUG)) {
Why not use tracepoints directly?
Because trace can't cope with you having to do an allocation/free.
+ char *sdebug, *ddebug;
+ sdebug = strdup(inet_ntoa(pkt->ip->ip_src));
+ ddebug = strdup(inet_ntoa(pkt->ip->ip_dst));
+ fprintf(stderr, "%s: src/dst: %s/%s p: seq/ack=%u/%u"
+ " flags=%x\n", __func__, sdebug, ddebug,
+ ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
+ tcp_pkt->th_flags);
However, this should use the trace_ call to write the result even
if it's
using trace_event_get_state to switch the whole block on/off.
I will fix it in next version.
+ g_free(sdebug);
+ g_free(ddebug);
+ }
+
+ if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK)) {
+ /* save primary colo tcp packet seq */
+ conn->primary_seq = ntohl(tcp_pkt->th_ack) - 1;
Looks like primary_seq will only be updated during handshake, I
wonder how
this works.
OK.
We assume that 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.
If I read your code correctly, secondary_seq will only be updated
during handshake. So the ack seq will always be same for each packet
received by secondary?
Yes. I don't know why kernel do this. But I dump the packet hex
found that,
the ack packet flag=ACK means only ack enabled.and the seq will
affect tcp checksum
make connection failed.
Not sure I get your meaning, but basically the code here should not
have any assumptions on guest behaviors.
Yes. I get your point.
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)
Is ACK a must here?
Yes.
Looks not, e.g what happens if guest does not use piggybacking acks?
If guest does not use piggybacking acks, it will send a independent
packet for ack.
we will get this packet.
like:
pkt(seq=xxxx,ack=xxx,flag=ACK).
Thanks
Zhang Chen
.
--
Thanks
zhangchen
