From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35474) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cgSYF-0004g3-Ly for qemu-devel@nongnu.org; Wed, 22 Feb 2017 03:45:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cgSYC-0003EK-GN for qemu-devel@nongnu.org; Wed, 22 Feb 2017 03:45:31 -0500 Received: from [45.249.212.189] (port=2402 helo=dggrg03-dlp.huawei.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_ARCFOUR_SHA1:16) (Exim 4.71) (envelope-from ) id 1cgSYB-0003Dq-Jc for qemu-devel@nongnu.org; Wed, 22 Feb 2017 03:45:28 -0500 References: <1487735198-127300-1-git-send-email-zhang.zhanghailiang@huawei.com> <1487735198-127300-3-git-send-email-zhang.zhanghailiang@huawei.com> From: Hailiang Zhang Message-ID: <58AD4F8F.5030703@huawei.com> Date: Wed, 22 Feb 2017 16:45:03 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH v2 2/3] filter-rewriter: fix memory leak for connection in connection_track_table List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jason Wang , zhangchen.fnst@cn.fujitsu.com, lizhijian@cn.fujitsu.com Cc: xuquan8@huawei.com, qemu-devel@nongnu.org, pss.wulizhen@huawei.com On 2017/2/22 16:07, Jason Wang wrote: > > > On 2017年02月22日 11:46, zhanghailiang wrote: >> After a net connection is closed, we didn't clear its releated resources >> in connection_track_table, which will lead to memory leak. > > Not a real leak but would lead reset of hash table if too many closed > connections. > Yes, you are right, there will be lots of stale connection data in hash table if we don't remove it while it is been closed. Which >> >> Let't track the state of net connection, if it is closed, its related >> resources will be cleared up. > > The issue is the state were tracked partially, do we need a full state > machine here? > Not, IMHO, we only care about the last state of it, because, we will do nothing even if we track the intermedial states. >> >> Signed-off-by: zhanghailiang >> --- >> net/colo.h | 4 +++ >> net/filter-rewriter.c | 70 +++++++++++++++++++++++++++++++++++++++++++++------ >> 2 files changed, 67 insertions(+), 7 deletions(-) >> >> diff --git a/net/colo.h b/net/colo.h >> index 7c524f3..cd9027f 100644 >> --- a/net/colo.h >> +++ b/net/colo.h >> @@ -18,6 +18,7 @@ >> #include "slirp/slirp.h" >> #include "qemu/jhash.h" >> #include "qemu/timer.h" >> +#include "slirp/tcp.h" >> >> #define HASHTABLE_MAX_SIZE 16384 >> >> @@ -69,6 +70,9 @@ typedef struct Connection { >> * run once in independent tcp connection >> */ >> int syn_flag; >> + >> + int tcp_state; /* TCP FSM state */ >> + tcp_seq fin_ack_seq; /* the seq of 'fin=1,ack=1' */ >> } Connection; >> >> uint32_t connection_key_hash(const void *opaque); >> diff --git a/net/filter-rewriter.c b/net/filter-rewriter.c >> index c4ab91c..7e7ec35 100644 >> --- a/net/filter-rewriter.c >> +++ b/net/filter-rewriter.c >> @@ -60,9 +60,9 @@ static int is_tcp_packet(Packet *pkt) >> } >> >> /* handle tcp packet from primary guest */ >> -static int handle_primary_tcp_pkt(NetFilterState *nf, >> +static int handle_primary_tcp_pkt(RewriterState *rf, >> Connection *conn, >> - Packet *pkt) >> + Packet *pkt, ConnectionKey *key) >> { >> struct tcphdr *tcp_pkt; >> >> @@ -97,15 +97,45 @@ static int handle_primary_tcp_pkt(NetFilterState *nf, >> tcp_pkt->th_ack = htonl(ntohl(tcp_pkt->th_ack) + conn->offset); >> >> net_checksum_calculate((uint8_t *)pkt->data, pkt->size); >> + /* >> + * Case 1: >> + * The *server* side of this connect is VM, *client* tries to close >> + * the connection. >> + * >> + * We got 'ack=1' packets from client side, it acks 'fin=1, ack=1' >> + * packet from server side. From this point, we can ensure that there >> + * will be no packets in the connection, except that, some errors >> + * happen between the path of 'filter object' and vNIC, if this rare >> + * case really happen, we can still create a new connection, >> + * So it is safe to remove the connection from connection_track_table. >> + * >> + */ >> + if ((conn->tcp_state == TCPS_LAST_ACK) && >> + (ntohl(tcp_pkt->th_ack) == (conn->fin_ack_seq + 1))) { >> + fprintf(stderr, "Remove conn " > > Can this even compile? > Oops, i forgot to remove it, will remove it in next version. >> + g_hash_table_remove(rf->connection_track_table, key); >> + } >> + } >> + /* >> + * Case 2: >> + * The *server* side of this connect is VM, *server* tries to close >> + * the connection. >> + * >> + * We got 'fin=1, ack=1' packet from client side, we need to >> + * record the seq of 'fin=1, ack=1' packet. >> + */ >> + if ((tcp_pkt->th_flags & (TH_ACK | TH_FIN)) == (TH_ACK | TH_FIN)) { >> + conn->fin_ack_seq = htonl(tcp_pkt->th_seq); >> + conn->tcp_state = TCPS_LAST_ACK; >> } >> >> return 0; >> } >> >> /* handle tcp packet from secondary guest */ >> -static int handle_secondary_tcp_pkt(NetFilterState *nf, >> +static int handle_secondary_tcp_pkt(RewriterState *rf, >> Connection *conn, >> - Packet *pkt) >> + Packet *pkt, ConnectionKey *key) >> { >> struct tcphdr *tcp_pkt; >> >> @@ -133,8 +163,34 @@ static int handle_secondary_tcp_pkt(NetFilterState *nf, >> tcp_pkt->th_seq = htonl(ntohl(tcp_pkt->th_seq) - conn->offset); >> >> net_checksum_calculate((uint8_t *)pkt->data, pkt->size); >> + /* >> + * Case 2: >> + * The *server* side of this connect is VM, *server* tries to close >> + * the connection. >> + * >> + * We got 'ack=1' packets from server side, it acks 'fin=1, ack=1' >> + * packet from client side. Like Case 1, there should be no packets >> + * in the connection from now know, But the difference here is >> + * if the packet is lost, We will get the resent 'fin=1,ack=1' packet. >> + * TODO: Fix above case. >> + */ >> + if ((conn->tcp_state == TCPS_LAST_ACK) && >> + (ntohl(tcp_pkt->th_ack) == (conn->fin_ack_seq + 1))) { >> + g_hash_table_remove(rf->connection_track_table, key); >> + } >> + } >> + /* >> + * Case 1: >> + * The *server* side of this connect is VM, *client* tries to close >> + * the connection. >> + * >> + * We got 'fin=1, ack=1' packet from server side, we need to >> + * record the seq of 'fin=1, ack=1' packet. >> + */ >> + if ((tcp_pkt->th_flags & (TH_ACK | TH_FIN)) == (TH_ACK | TH_FIN)) { >> + conn->fin_ack_seq = ntohl(tcp_pkt->th_seq); >> + conn->tcp_state = TCPS_LAST_ACK; > > I thought the tcp_state should store the state of TCP from the view of > secondary VM? So TCPS_LAST_ACK is wrong and bring lots of confusion. And > the handle of active close needs more states here. E.g if connection is > in FIN_WAIT_2, the connection is only half closed, remote peer can still > send packet to us unless we receive a FIN. > Yes, i know what you mean, actually, here, we try to only track the last two steps for closing a connection, that is 'fin=1,ack=1,seq=2,ack=u+1' and 'ack=1,seq=u+1,ack=w+1', because if we get a 'fin=1,ack=1', we can ensure that the 'fin=1,seq=u' packet has been posted. Another reason is we may can't track the 'fin=1,seq=u' packet while we start COLO while one connection is closing, which the 'fin=1,seq=u' packet has been posted. Actually, here, if we start COLO while one connection is closing, which the 'fin=1,ack=1' has been posted, we can only track 'ack=1' packet. In this case, the connection will be left in hash table for ever though it is harmless. Any ideas for this case ? For the above codes question, i'd like to change tcp_state to tap_closing_wait, is it OK ? Thanks. Hailiang > Thanks > >> } >> - >> return 0; >> } >> >> @@ -178,7 +234,7 @@ static ssize_t colo_rewriter_receive_iov(NetFilterState *nf, >> >> if (sender == nf->netdev) { >> /* NET_FILTER_DIRECTION_TX */ >> - if (!handle_primary_tcp_pkt(nf, conn, pkt)) { >> + if (!handle_primary_tcp_pkt(s, conn, pkt, &key)) { >> qemu_net_queue_send(s->incoming_queue, sender, 0, >> (const uint8_t *)pkt->data, pkt->size, NULL); >> packet_destroy(pkt, NULL); >> @@ -191,7 +247,7 @@ static ssize_t colo_rewriter_receive_iov(NetFilterState *nf, >> } >> } else { >> /* NET_FILTER_DIRECTION_RX */ >> - if (!handle_secondary_tcp_pkt(nf, conn, pkt)) { >> + if (!handle_secondary_tcp_pkt(s, conn, pkt, &key)) { >> qemu_net_queue_send(s->incoming_queue, sender, 0, >> (const uint8_t *)pkt->data, pkt->size, NULL); >> packet_destroy(pkt, NULL); > > > . >