| Message ID | 0fd5a076b6cc41eab247d9b892061af5@jd.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [ovs-dev] 答复: [PATCH] conntrack: add tcp_in_liberal option in userspace conntrack | expand |
On Mon, Jun 3, 2019 at 7:59 PM 姜立东 <jianglidong3@jd.com> wrote: > Hi Darrell, > > > > The “tighter checking” on TCP_RST in kernel, do you mean processes under “TCP_CONNTRACK_CLOSE” > case? > > There is only one situation(when th->seq is less than peer td_maxack, as > mentioned) may leads to explicitly –NF_ACCEPT, kernel implementation just > lets most TCP_RST packets pass when TCP liberal mode is enabled. > yep, this is the tighter checking the kernel does for RSTs in general Userspace code has a tighter check for RSTs > > > Meanwhile, I think the purpose of TCP liberal mode is to skip TCP SEQ > check in conntrack, when SEQ out of sync is normal situation in some > application scenarios. > For example, TCP_RST packets can have very different SEQ than what is > captured in conntrack in hardware-offloading scenario, because most of > packets are forwarded by hardware. > TCP resets are used in selected valid scenarios, but are more often associated with DOS scenarios, so they are a special case Removing most or all protection from reset attacks seems irresponsible. Hardware offload implementations can be done well or poorly; catering to poor implementations at the cost to every other use case may not be the best approach. In this scenario, TCP_RST can work normally with kernel TCP liberal mode > because it is passed to destination, but won’t work with user space > conntrack with current change due to being dropped. > > > I think tighter check is good for normal situation, but may be conflict > with the purpose of TCP liberal mode by putting more limitations. > > > BR, Lidong > > > > *发件人:* Darrell Ball <dlu998@gmail.com> > *发送时间:* 2019年6月3日 23:53 > *收件人:* 姜立东 <jianglidong3@jd.com> > *抄送:* dev@openvswitch.org; 王志克 <wangzhike@jd.com> > *主题:* Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in > userspace conntrack > > > > > > > > On Mon, Jun 3, 2019 at 12:21 AM 姜立东 <jianglidong3@jd.com> wrote: > > Hi Darrell, > > > > By checking latest patch, we notice it has inconsistent behavior on > TCP_RST packet with > > kernel tcp_liberal option. > > In kernel, TCP_RST packet is only checked for TCP_CONNTRACK_CLOSE state, > > > > TCP_CONNTRACK_CLOSE is the 'next state' on receiving RST > > > > > > TCP_RST > > packet is dropped if its seq is less than peer acked. > > In other cases, TCP_RST packets are processed in tcp_in_window() as > other packets, if > > tcp_liberal is enabled, they always are accepted. > > > > On receipt of a RST in any present state, tighter checking is done; this > checking is done > > before *tcp_in_window* > <https://elixir.bootlin.com/linux/v4.9.12/ident/tcp_in_window>() is > executed. > > > > Do you mean “tighter checking” is processes under “TCP_CONNTRACK_CLOSE” > case? There is > > > > Please refer to tcp_packet() and tcp_in_window() in kernel conntrack. > > > > Current implementation may cause TCP_RST packet is marked as INVALID by > conntrack > > due to old seq info in conntrack in hardware-offloading scenario. > > So that we suggest to move conntrack_get_tcp_liberal(ct) up in this check > to include > > TCP_RST packet as below, > > > > I think the tighter checking for RSTs I am proposing is generally > consistent, although BSD and > > Linux are somewhat different. > > > > > > > > - if (SEQ_GEQ(src->seqhi, end) > > - /* Last octet inside other's window space */ > > - && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) > > - /* Retrans: not more than one window back */ > > - && (ackskew >= -MAXACKWINDOW) > > - /* Acking not more than one reassembled fragment backwards */ > > - && (ackskew <= (MAXACKWINDOW << sws)) > > - /* Acking not more than one window forward */ > > + if ((SEQ_GEQ(src->seqhi, end) > > + /* Last octet inside other's window space */ > > + && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) > > + /* Retrans: not more than one window back */ > > + && ackskew >= -MAXACKWINDOW > > + /* Acking not more than one reassembled fragment backwards */ > > + && ackskew <= (MAXACKWINDOW << sws)) > > + /* Acking not more than one window forward */ > > && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo > > - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) { > > + || (orig_seq == src->seqlo + 1) > > + || (orig_seq + 1 == src->seqlo))) > > + || conntrack_get_tcp_liberal(ct)) { > > > > > > > > Thanks, > > Lidong > > > > *发件人:* Darrell Ball <dlu998@gmail.com> > *发送时间:* 2019年6月1日 2:11 > *收件人:* 姜立东 <jianglidong3@jd.com> > *抄送:* dev@openvswitch.org; 王志克 <wangzhike@jd.com> > *主题:* Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in > userspace conntrack > > > > > > > > On Fri, May 31, 2019 at 9:40 AM Darrell Ball <dlu998@gmail.com> wrote: > > > > > > On Fri, May 31, 2019 at 2:42 AM 姜立东 <jianglidong3@jd.com> wrote: > > Hi Darrell, > > > > Thanks for prompt action. > > > > I think there are 2 main differences in your change, > > 1. Replace Open_vswitch.other_config by dpctl CLI command. > > 2. One more case to check tcp_liberal as below. > > @@ -333,10 +335,12 @@ tcp_conn_update(struct conntrack *ct, struct conn > *conn_, > > } else if ((dst->state < CT_DPIF_TCPS_SYN_SENT > > || dst->state >= CT_DPIF_TCPS_FIN_WAIT_2 > > || src->state >= CT_DPIF_TCPS_FIN_WAIT_2) > > - && SEQ_GEQ(src->seqhi + MAXACKWINDOW, end) > > - /* Within a window forward of the originating packet */ > > - && SEQ_GEQ(seq, src->seqlo - MAXACKWINDOW)) { > > - /* Within a window backward of the originating packet */ > > + && ((SEQ_GEQ(src->seqhi + MAXACKWINDOW, end) > > + /* Within a window forward of the originating packet > */ > > + && SEQ_GEQ(seq, src->seqlo - MAXACKWINDOW)) > > + /* Within a window backward of the originating packet > */ > > + || (conntrack_get_tcp_liberal(ct) > > + && (tcp_flags & TCP_RST) == 0))) > > For item 1, it is fine for us. > > For item 2, we didn’t actually hit into this conditional branch in our > application, but considering conntrack is in the middle of this path, > > it is reasonable to add this check and leave SEQ validation to endpoints’ > local TCP state machine. So it looks good to us. > > > > Lidong > > > > I just noticed you were referring to the "else if" condition above > > This change had been dropped in v2 since it is not needed, here: > > > > https://patchwork.ozlabs.org/patch/1107761/ > > > > The change in the 'if' condition check is the main algorithm change; you > might want to > > compare it to the proposed change that you had sent out. > > > > Thanks Darrell > > > > > > > > *diff --git a/lib/conntrack-tcp.c b/lib/conntrack-tcp.c* > > *index 397aca1..e95d2f3 100644* > > *--- a/lib/conntrack-tcp.c* > > *+++ b/lib/conntrack-tcp.c* > > *@@ -272,16 +272,18 @@* tcp_conn_update(struct conntrack *ct, struct conn *conn_, > > int ackskew = check_ackskew ? dst->seqlo - ack : 0; > > #define MAXACKWINDOW (0xffff + 1500) /* 1500 is an arbitrary fudge factor */ > > - if (SEQ_GEQ(src->seqhi, end) > > - /* Last octet inside other's window space */ > > - && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) > > - /* Retrans: not more than one window back */ > > - && (ackskew >= -MAXACKWINDOW) > > - /* Acking not more than one reassembled fragment backwards */ > > - && (ackskew <= (MAXACKWINDOW << sws)) > > - /* Acking not more than one window forward */ > > + if (((SEQ_GEQ(src->seqhi, end) > > + /* Last octet inside other's window space */ > > + && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) > > + /* Retrans: not more than one window back */ > > + && ackskew >= -MAXACKWINDOW > > + /* Acking not more than one reassembled fragment backwards */ > > + && ackskew <= (MAXACKWINDOW << sws)) > > + || conntrack_get_tcp_liberal(ct)) > > + /* Acking not more than one window forward */ > > && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo > > - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) { > > + || (orig_seq == src->seqlo + 1) > > + || (orig_seq + 1 == src->seqlo))) { > > /* Require an exact/+1 sequence match on resets when possible */ > > /* update max window */ > > > > > > > > > > > > Thanks Lidong > > > > The algorithm I used adheres to the liberal mode definition. > > > > For future reference, another important aspect is test support. > > > > Darrell > > > > > > BR, > > Lidong > > > > *发件人:* Darrell Ball <dlu998@gmail.com> > *发送时间:* 2019年5月30日 14:51 > *收件人:* 姜立东 <jianglidong3@jd.com> > *抄送:* dev@openvswitch.org; 王志克 <wangzhike@jd.com> > *主题:* Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in > userspace conntrack > > > > Hi Lidong/Zhike > > > > I sent an alternative implementation: > https://mail.openvswitch.org/pipermail/ovs-dev/2019-May/359364.html > > > > Pls take a look and check if it meets your requirements. > > > > Thanks Darrell > > > > On Fri, May 24, 2019 at 10:11 AM Darrell Ball <dlu998@gmail.com> wrote: > > Thanks for the patch Lidong/Zhike > > > > I took an initial look and will send a response next week. > > > > Darrell > > > > On Tue, May 21, 2019 at 8:53 PM 姜立东 <jianglidong3@jd.com> wrote: > > From 3ce112684921bca74839e109fda91848aa024a54 Mon Sep 17 00:00:00 2001 > From: Jiang Lidong <jianglidong3@jd.com> > Date: Wed, 22 May 2019 11:21:34 +0800 > Subject: [PATCH] conntrack: add tcp_in_liberal option in userspace > conntrack > > Adding similar cp_in_liberal option in userspace conntrack as > kernel conntrack does to skip seq check on tcp connection. > It prevents packet is marked as INVALID by stable seq > info in conntrack connection. > > This option can help to make traffic survive in hardware > offloading cases, especially when traffic is being moved > back to software path from hardware forwarding engine. > > Signed-off-by: Lidong Jiang <jianglidong3@jd.com> > Signed-off-by: Zhike Wang <wangzhike@jd.com> > > --- > lib/conntrack-private.h | 2 ++ > lib/conntrack-tcp.c | 5 +++-- > lib/conntrack.c | 6 ++++++ > lib/conntrack.h | 4 +++- > lib/dpif-netdev.c | 6 ++++++ > 5 files changed, 20 insertions(+), 3 deletions(-) > > diff --git a/lib/conntrack-private.h b/lib/conntrack-private.h > index 51b7d7f..9bc99cd 100644 > --- a/lib/conntrack-private.h > +++ b/lib/conntrack-private.h > @@ -172,6 +172,8 @@ struct conntrack { > /* Fragmentation handling context. */ > struct ipf *ipf; > + > + bool tcp_be_liberal; > }; > /* Lock acquisition order: > diff --git a/lib/conntrack-tcp.c b/lib/conntrack-tcp.c > index 397aca1..61abafb 100644 > --- a/lib/conntrack-tcp.c > +++ b/lib/conntrack-tcp.c > @@ -272,7 +272,7 @@ tcp_conn_update(struct conntrack *ct, struct conn > *conn_, > int ackskew = check_ackskew ? dst->seqlo - ack : 0; > #define MAXACKWINDOW (0xffff + 1500) /* 1500 is an arbitrary fudge > factor */ > - if (SEQ_GEQ(src->seqhi, end) > + if ((SEQ_GEQ(src->seqhi, end) > /* Last octet inside other's window space */ > && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) > /* Retrans: not more than one window back */ > @@ -281,7 +281,8 @@ tcp_conn_update(struct conntrack *ct, struct conn > *conn_, > && (ackskew <= (MAXACKWINDOW << sws)) > /* Acking not more than one window forward */ > && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo > - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == > src->seqlo))) { > + || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == > src->seqlo))) > + || (ct->tcp_be_liberal)) { > /* Require an exact/+1 sequence match on resets when possible */ > /* update max window */ > diff --git a/lib/conntrack.c b/lib/conntrack.c > index 6711f5e..bd92710 100644 > --- a/lib/conntrack.c > +++ b/lib/conntrack.c > @@ -2282,6 +2282,12 @@ conntrack_ipf_ctx(struct conntrack *ct) > return ct->ipf; > } > +void > +conntrack_set_tcp_be_liberal(struct conntrack *ct, bool enabled) > +{ > + ct->tcp_be_liberal = enabled; > +} > + > int > conntrack_dump_start(struct conntrack *ct, struct conntrack_dump *dump, > const uint16_t *pzone, int *ptot_bkts) > diff --git a/lib/conntrack.h b/lib/conntrack.h > index 2012150..b8d799d 100644 > --- a/lib/conntrack.h > +++ b/lib/conntrack.h > @@ -119,5 +119,7 @@ int conntrack_set_maxconns(struct conntrack *ct, > uint32_t maxconns); > int conntrack_get_maxconns(struct conntrack *ct, uint32_t *maxconns); > int conntrack_get_nconns(struct conntrack *ct, uint32_t *nconns); > struct ipf *conntrack_ipf_ctx(struct conntrack *ct); > - > + > +void conntrack_set_tcp_be_liberal(struct conntrack *ct, bool enabled); > + > #endif /* conntrack.h */ > diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c > index 5a6f2ab..ae6a18e 100644 > --- a/lib/dpif-netdev.c > +++ b/lib/dpif-netdev.c > @@ -3823,6 +3823,12 @@ dpif_netdev_set_config(struct dpif *dpif, const > struct smap *other_config) > uint32_t tx_flush_interval, cur_tx_flush_interval; > uint64_t rebalance_intvl; > + bool tcp_be_liberal = smap_get_bool(other_config, > + "conntrack_tcp_be_liberal", > + false); > + > + conntrack_set_tcp_be_liberal(&dp->conntrack, tcp_be_liberal); > + > tx_flush_interval = smap_get_int(other_config, "tx-flush-interval", > DEFAULT_TX_FLUSH_INTERVAL); > atomic_read_relaxed(&dp->tx_flush_interval, &cur_tx_flush_interval); > -- > 1.8.3.1 > > _______________________________________________ > dev mailing list > dev@openvswitch.org > https://mail.openvswitch.org/mailman/listinfo/ovs-dev > >
diff --git a/lib/conntrack-private.h b/lib/conntrack-private.h index 51b7d7f..9bc99cd 100644 --- a/lib/conntrack-private.h +++ b/lib/conntrack-private.h @@ -172,6 +172,8 @@ struct conntrack { /* Fragmentation handling context. */ struct ipf *ipf; + + bool tcp_be_liberal; }; /* Lock acquisition order: diff --git a/lib/conntrack-tcp.c b/lib/conntrack-tcp.c index 397aca1..61abafb 100644 --- a/lib/conntrack-tcp.c +++ b/lib/conntrack-tcp.c @@ -272,7 +272,7 @@ tcp_conn_update(struct conntrack *ct, struct conn *conn_, int ackskew = check_ackskew ? dst->seqlo - ack : 0; #define MAXACKWINDOW (0xffff + 1500) /* 1500 is an arbitrary fudge factor */ - if (SEQ_GEQ(src->seqhi, end) + if ((SEQ_GEQ(src->seqhi, end) /* Last octet inside other's window space */ && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) /* Retrans: not more than one window back */ @@ -281,7 +281,8 @@ tcp_conn_update(struct conntrack *ct, struct conn *conn_, && (ackskew <= (MAXACKWINDOW << sws)) /* Acking not more than one window forward */ && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) { + || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) + || (ct->tcp_be_liberal)) { /* Require an exact/+1 sequence match on resets when possible */ /* update max window */ diff --git a/lib/conntrack.c b/lib/conntrack.c index 6711f5e..bd92710 100644 --- a/lib/conntrack.c +++ b/lib/conntrack.c @@ -2282,6 +2282,12 @@ conntrack_ipf_ctx(struct conntrack *ct) return ct->ipf; } +void +conntrack_set_tcp_be_liberal(struct conntrack *ct, bool enabled) +{ + ct->tcp_be_liberal = enabled; +} + int conntrack_dump_start(struct conntrack *ct, struct conntrack_dump *dump, const uint16_t *pzone, int *ptot_bkts) diff --git a/lib/conntrack.h b/lib/conntrack.h index 2012150..b8d799d 100644 --- a/lib/conntrack.h +++ b/lib/conntrack.h @@ -119,5 +119,7 @@ int conntrack_set_maxconns(struct conntrack *ct, uint32_t maxconns); int conntrack_get_maxconns(struct conntrack *ct, uint32_t *maxconns); int conntrack_get_nconns(struct conntrack *ct, uint32_t *nconns); struct ipf *conntrack_ipf_ctx(struct conntrack *ct); - + +void conntrack_set_tcp_be_liberal(struct conntrack *ct, bool enabled); + #endif /* conntrack.h */ diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index 5a6f2ab..ae6a18e 100644 --- a/lib/dpif-netdev.c +++ b/lib/dpif-netdev.c @@ -3823,6 +3823,12 @@ dpif_netdev_set_config(struct dpif *dpif, const struct smap *other_config) uint32_t tx_flush_interval, cur_tx_flush_interval; uint64_t rebalance_intvl; + bool tcp_be_liberal = smap_get_bool(other_config, + "conntrack_tcp_be_liberal", + false); + + conntrack_set_tcp_be_liberal(&dp->conntrack, tcp_be_liberal); + tx_flush_interval = smap_get_int(other_config, "tx-flush-interval", DEFAULT_TX_FLUSH_INTERVAL); atomic_read_relaxed(&dp->tx_flush_interval, &cur_tx_flush_interval); -- 1.8.3.1
Hi Darrell, The “tighter checking” on TCP_RST in kernel, do you mean processes under “TCP_CONNTRACK_CLOSE” case? There is only one situation(when th->seq is less than peer td_maxack, as mentioned) may leads to explicitly –NF_ACCEPT, kernel implementation just lets most TCP_RST packets pass when TCP liberal mode is enabled. Meanwhile, I think the purpose of TCP liberal mode is to skip TCP SEQ check in conntrack, when SEQ out of sync is normal situation in some application scenarios. For example, TCP_RST packets can have very different SEQ than what is captured in conntrack in hardware-offloading scenario, because most of packets are forwarded by hardware. In this scenario, TCP_RST can work normally with kernel TCP liberal mode because it is passed to destination, but won’t work with user space conntrack with current change due to being dropped. I think tighter check is good for normal situation, but may be conflict with the purpose of TCP liberal mode by putting more limitations. BR, Lidong 发件人: Darrell Ball <dlu998@gmail.com> 发送时间: 2019年6月3日 23:53 收件人: 姜立东 <jianglidong3@jd.com> 抄送: dev@openvswitch.org; 王志克 <wangzhike@jd.com> 主题: Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in userspace conntrack On Mon, Jun 3, 2019 at 12:21 AM 姜立东 <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> wrote: Hi Darrell, By checking latest patch, we notice it has inconsistent behavior on TCP_RST packet with kernel tcp_liberal option. In kernel, TCP_RST packet is only checked for TCP_CONNTRACK_CLOSE state, TCP_CONNTRACK_CLOSE is the 'next state' on receiving RST TCP_RST packet is dropped if its seq is less than peer acked. In other cases, TCP_RST packets are processed in tcp_in_window() as other packets, if tcp_liberal is enabled, they always are accepted. On receipt of a RST in any present state, tighter checking is done; this checking is done before tcp_in_window<https://elixir.bootlin.com/linux/v4.9.12/ident/tcp_in_window>() is executed. Do you mean “tighter checking” is processes under “TCP_CONNTRACK_CLOSE” case? There is Please refer to tcp_packet() and tcp_in_window() in kernel conntrack. Current implementation may cause TCP_RST packet is marked as INVALID by conntrack due to old seq info in conntrack in hardware-offloading scenario. So that we suggest to move conntrack_get_tcp_liberal(ct) up in this check to include TCP_RST packet as below, I think the tighter checking for RSTs I am proposing is generally consistent, although BSD and Linux are somewhat different. - if (SEQ_GEQ(src->seqhi, end) - /* Last octet inside other's window space */ - && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) - /* Retrans: not more than one window back */ - && (ackskew >= -MAXACKWINDOW) - /* Acking not more than one reassembled fragment backwards */ - && (ackskew <= (MAXACKWINDOW << sws)) - /* Acking not more than one window forward */ + if ((SEQ_GEQ(src->seqhi, end) + /* Last octet inside other's window space */ + && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) + /* Retrans: not more than one window back */ + && ackskew >= -MAXACKWINDOW + /* Acking not more than one reassembled fragment backwards */ + && ackskew <= (MAXACKWINDOW << sws)) + /* Acking not more than one window forward */ && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) { + || (orig_seq == src->seqlo + 1) + || (orig_seq + 1 == src->seqlo))) + || conntrack_get_tcp_liberal(ct)) { Thanks, Lidong 发件人: Darrell Ball <dlu998@gmail.com<mailto:dlu998@gmail.com>> 发送时间: 2019年6月1日 2:11 收件人: 姜立东 <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> 抄送: dev@openvswitch.org<mailto:dev@openvswitch.org>; 王志克 <wangzhike@jd.com<mailto:wangzhike@jd.com>> 主题: Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in userspace conntrack On Fri, May 31, 2019 at 9:40 AM Darrell Ball <dlu998@gmail.com<mailto:dlu998@gmail.com>> wrote: On Fri, May 31, 2019 at 2:42 AM 姜立东 <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> wrote: Hi Darrell, Thanks for prompt action. I think there are 2 main differences in your change, 1. Replace Open_vswitch.other_config by dpctl CLI command. 2. One more case to check tcp_liberal as below. @@ -333,10 +335,12 @@ tcp_conn_update(struct conntrack *ct, struct conn *conn_, } else if ((dst->state < CT_DPIF_TCPS_SYN_SENT || dst->state >= CT_DPIF_TCPS_FIN_WAIT_2 || src->state >= CT_DPIF_TCPS_FIN_WAIT_2) - && SEQ_GEQ(src->seqhi + MAXACKWINDOW, end) - /* Within a window forward of the originating packet */ - && SEQ_GEQ(seq, src->seqlo - MAXACKWINDOW)) { - /* Within a window backward of the originating packet */ + && ((SEQ_GEQ(src->seqhi + MAXACKWINDOW, end) + /* Within a window forward of the originating packet */ + && SEQ_GEQ(seq, src->seqlo - MAXACKWINDOW)) + /* Within a window backward of the originating packet */ + || (conntrack_get_tcp_liberal(ct) + && (tcp_flags & TCP_RST) == 0))) For item 1, it is fine for us. For item 2, we didn’t actually hit into this conditional branch in our application, but considering conntrack is in the middle of this path, it is reasonable to add this check and leave SEQ validation to endpoints’ local TCP state machine. So it looks good to us. Lidong I just noticed you were referring to the "else if" condition above This change had been dropped in v2 since it is not needed, here: https://patchwork.ozlabs.org/patch/1107761/ The change in the 'if' condition check is the main algorithm change; you might want to compare it to the proposed change that you had sent out. Thanks Darrell diff --git a/lib/conntrack-tcp.c b/lib/conntrack-tcp.c index 397aca1..e95d2f3 100644 --- a/lib/conntrack-tcp.c +++ b/lib/conntrack-tcp.c @@ -272,16 +272,18 @@ tcp_conn_update(struct conntrack *ct, struct conn *conn_, int ackskew = check_ackskew ? dst->seqlo - ack : 0; #define MAXACKWINDOW (0xffff + 1500) /* 1500 is an arbitrary fudge factor */ - if (SEQ_GEQ(src->seqhi, end) - /* Last octet inside other's window space */ - && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) - /* Retrans: not more than one window back */ - && (ackskew >= -MAXACKWINDOW) - /* Acking not more than one reassembled fragment backwards */ - && (ackskew <= (MAXACKWINDOW << sws)) - /* Acking not more than one window forward */ + if (((SEQ_GEQ(src->seqhi, end) + /* Last octet inside other's window space */ + && SEQ_GEQ(seq, src->seqlo - (dst->max_win << dws)) + /* Retrans: not more than one window back */ + && ackskew >= -MAXACKWINDOW + /* Acking not more than one reassembled fragment backwards */ + && ackskew <= (MAXACKWINDOW << sws)) + || conntrack_get_tcp_liberal(ct)) + /* Acking not more than one window forward */ && ((tcp_flags & TCP_RST) == 0 || orig_seq == src->seqlo - || (orig_seq == src->seqlo + 1) || (orig_seq + 1 == src->seqlo))) { + || (orig_seq == src->seqlo + 1) + || (orig_seq + 1 == src->seqlo))) { /* Require an exact/+1 sequence match on resets when possible */ /* update max window */ Thanks Lidong The algorithm I used adheres to the liberal mode definition. For future reference, another important aspect is test support. Darrell BR, Lidong 发件人: Darrell Ball <dlu998@gmail.com<mailto:dlu998@gmail.com>> 发送时间: 2019年5月30日 14:51 收件人: 姜立东 <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> 抄送: dev@openvswitch.org<mailto:dev@openvswitch.org>; 王志克 <wangzhike@jd.com<mailto:wangzhike@jd.com>> 主题: Re: [ovs-dev] [PATCH] conntrack: add tcp_in_liberal option in userspace conntrack Hi Lidong/Zhike I sent an alternative implementation: https://mail.openvswitch.org/pipermail/ovs-dev/2019-May/359364.html Pls take a look and check if it meets your requirements. Thanks Darrell On Fri, May 24, 2019 at 10:11 AM Darrell Ball <dlu998@gmail.com<mailto:dlu998@gmail.com>> wrote: Thanks for the patch Lidong/Zhike I took an initial look and will send a response next week. Darrell On Tue, May 21, 2019 at 8:53 PM 姜立东 <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> wrote: From 3ce112684921bca74839e109fda91848aa024a54 Mon Sep 17 00:00:00 2001 From: Jiang Lidong <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> Date: Wed, 22 May 2019 11:21:34 +0800 Subject: [PATCH] conntrack: add tcp_in_liberal option in userspace conntrack Adding similar cp_in_liberal option in userspace conntrack as kernel conntrack does to skip seq check on tcp connection. It prevents packet is marked as INVALID by stable seq info in conntrack connection. This option can help to make traffic survive in hardware offloading cases, especially when traffic is being moved back to software path from hardware forwarding engine. Signed-off-by: Lidong Jiang <jianglidong3@jd.com<mailto:jianglidong3@jd.com>> Signed-off-by: Zhike Wang <wangzhike@jd.com<mailto:wangzhike@jd.com>> --- lib/conntrack-private.h | 2 ++ lib/conntrack-tcp.c | 5 +++-- lib/conntrack.c | 6 ++++++ lib/conntrack.h | 4 +++- lib/dpif-netdev.c | 6 ++++++ 5 files changed, 20 insertions(+), 3 deletions(-)