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filter-rewriter: rewrite tcp packet to keep secondary connection

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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 <zhangchen.fnst@cn.fujitsu.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
This commit is contained in:
Zhang Chen 2016-09-27 10:22:34 +08:00 committed by Jason Wang
parent afe4612409
commit 30656b097e
4 changed files with 124 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/colo.c
View File

@ -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);

7
net/colo.h
View File

@ -62,6 +62,13 @@ typedef struct Connection {
/* flag to enqueue unprocessed_connections */
bool processing;
uint8_t ip_proto;
/* offset = secondary_seq - primary_seq */
tcp_seq offset;
/*
* we use this flag update offset func
* run once in independent tcp connection
*/
int syn_flag;
} Connection;
uint32_t connection_key_hash(const void *opaque);

112
net/filter-rewriter.c
View File

@ -10,6 +10,7 @@
*/
#include "qemu/osdep.h"
#include "trace.h"
#include "net/colo.h"
#include "net/filter.h"
#include "net/net.h"
@ -58,6 +59,93 @@ static int is_tcp_packet(Packet *pkt)
}
}
/* handle tcp packet from primary guest */
static int handle_primary_tcp_pkt(NetFilterState *nf,
Connection *conn,
Packet *pkt)
{
struct tcphdr *tcp_pkt;
tcp_pkt = (struct tcphdr *)pkt->transport_header;
if (trace_event_get_state(TRACE_COLO_FILTER_REWRITER_DEBUG)) {
char *sdebug, *ddebug;
sdebug = strdup(inet_ntoa(pkt->ip->ip_src));
ddebug = strdup(inet_ntoa(pkt->ip->ip_dst));
trace_colo_filter_rewriter_pkt_info(__func__, sdebug, ddebug,
ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
tcp_pkt->th_flags);
trace_colo_filter_rewriter_conn_offset(conn->offset);
g_free(sdebug);
g_free(ddebug);
}
if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_SYN)) {
/*
* we use this flag update offset func
* run once in independent tcp connection
*/
conn->syn_flag = 1;
}
if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK)) {
if (conn->syn_flag) {
/*
* offset = secondary_seq - primary seq
* ack packet sent by guest from primary node,
* so we use th_ack - 1 get primary_seq
*/
conn->offset -= (ntohl(tcp_pkt->th_ack) - 1);
conn->syn_flag = 0;
}
/* handle packets to the secondary from the primary */
tcp_pkt->th_ack = htonl(ntohl(tcp_pkt->th_ack) + conn->offset);
net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
}
return 0;
}
/* handle tcp packet from secondary guest */
static int handle_secondary_tcp_pkt(NetFilterState *nf,
Connection *conn,
Packet *pkt)
{
struct tcphdr *tcp_pkt;
tcp_pkt = (struct tcphdr *)pkt->transport_header;
if (trace_event_get_state(TRACE_COLO_FILTER_REWRITER_DEBUG)) {
char *sdebug, *ddebug;
sdebug = strdup(inet_ntoa(pkt->ip->ip_src));
ddebug = strdup(inet_ntoa(pkt->ip->ip_dst));
trace_colo_filter_rewriter_pkt_info(__func__, sdebug, ddebug,
ntohl(tcp_pkt->th_seq), ntohl(tcp_pkt->th_ack),
tcp_pkt->th_flags);
trace_colo_filter_rewriter_conn_offset(conn->offset);
g_free(sdebug);
g_free(ddebug);
}
if (((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == (TH_ACK | TH_SYN))) {
/*
* save offset = secondary_seq and then
* in handle_primary_tcp_pkt make offset
* = secondary_seq - primary_seq
*/
conn->offset = ntohl(tcp_pkt->th_seq);
}
if ((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK) {
/* handle packets to the primary from the secondary*/
tcp_pkt->th_seq = htonl(ntohl(tcp_pkt->th_seq) - conn->offset);
net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
}
return 0;
}
static ssize_t colo_rewriter_receive_iov(NetFilterState *nf,
NetClientState *sender,
unsigned flags,
@ -97,10 +185,30 @@ static ssize_t colo_rewriter_receive_iov(NetFilterState *nf,
if (sender == nf->netdev) {
/* NET_FILTER_DIRECTION_TX */
/* handle_primary_tcp_pkt */
if (!handle_primary_tcp_pkt(nf, conn, pkt)) {
qemu_net_queue_send(s->incoming_queue, sender, 0,
(const uint8_t *)pkt->data, pkt->size, NULL);
packet_destroy(pkt, NULL);
pkt = NULL;
/*
* We block the packet here,after rewrite pkt
* and will send it
*/
return 1;
}
} else {
/* NET_FILTER_DIRECTION_RX */
/* handle_secondary_tcp_pkt */
if (!handle_secondary_tcp_pkt(nf, conn, pkt)) {
qemu_net_queue_send(s->incoming_queue, sender, 0,
(const uint8_t *)pkt->data, pkt->size, NULL);
packet_destroy(pkt, NULL);
pkt = NULL;
/*
* We block the packet here,after rewrite pkt
* and will send it
*/
return 1;
}
}
}

5
trace-events
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@ -150,6 +150,11 @@ colo_compare_ip_info(int psize, const char *sta, const char *stb, int ssize, con
colo_old_packet_check_found(int64_t old_time) "%" PRId64
colo_compare_miscompare(void) ""
# net/filter-rewriter.c
colo_filter_rewriter_debug(void) ""
colo_filter_rewriter_pkt_info(const char *func, const char *src, const char *dst, uint32_t seq, uint32_t ack, uint32_t flag) "%s: src/dst: %s/%s p: seq/ack=%u/%u flags=%x\n"
colo_filter_rewriter_conn_offset(uint32_t offset) ": offset=%u\n"
### Guest events, keep at bottom
# @vaddr: Access' virtual address.