On 3/27/24 16:55, Mike Pattrick wrote:
> This patch adopts the proposed RFC 6935 by allowing null UDP checksums
> even if the tunnel protocol is IPv6. This is already supported by Linux
> through the udp6zerocsumtx tunnel option. It is disabled by default and
> IPv6 tunnels are flagged as requiring a checksum, but this patch enables
> the user to set csum=false on IPv6 tunnels.
>
> Signed-off-by: Mike Pattrick <m...@redhat.com>
> ---
> v2: Changed documentation, and added a NEWS item
> v3: NEWS file merge conflict
> v4: Better comments, new test
> v5: Addressed identified nit's
> ---
> NEWS | 4 ++++
> lib/netdev-native-tnl.c | 2 +-
> lib/netdev-vport.c | 17 +++++++++++++++--
> lib/netdev.h | 18 +++++++++++++++++-
> ofproto/tunnel.c | 10 ++++++++--
> tests/tunnel-push-pop-ipv6.at | 9 +++++++++
> tests/tunnel-push-pop.at | 7 +++++++
> tests/tunnel.at | 2 +-
> vswitchd/vswitch.xml | 12 +++++++++---
> 9 files changed, 71 insertions(+), 10 deletions(-)
>
> diff --git a/NEWS b/NEWS
> index c9e4064e6..6c8c4a2dc 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -4,6 +4,10 @@ Post-v3.3.0
> * Conntrack now supports 'random' flag for selecting ports in a range
> while natting and 'persistent' flag for selection of the IP address
> from a range.
> + * IPv6 UDP tunnel encapsulation including Geneve and VXLAN will now
> + honour the csum option. Configuring the interface with
> + "options:csum=false" now has the same effect as the udp6zerocsumtx
> + option has with Linux kernel UDP tunnels.
>
>
> v3.3.0 - 16 Feb 2024
> diff --git a/lib/netdev-native-tnl.c b/lib/netdev-native-tnl.c
> index dee9ab344..e8258bc4e 100644
> --- a/lib/netdev-native-tnl.c
> +++ b/lib/netdev-native-tnl.c
> @@ -424,7 +424,7 @@ udp_build_header(const struct netdev_tunnel_config
> *tnl_cfg,
> udp = netdev_tnl_ip_build_header(data, params, IPPROTO_UDP, 0);
> udp->udp_dst = tnl_cfg->dst_port;
>
> - if (params->is_ipv6 || params->flow->tunnel.flags & FLOW_TNL_F_CSUM) {
> + if (params->flow->tunnel.flags & FLOW_TNL_F_CSUM) {
> /* Write a value in now to mark that we should compute the checksum
> * later. 0xffff is handy because it is transparent to the
> * calculation. */
> diff --git a/lib/netdev-vport.c b/lib/netdev-vport.c
> index 60caa02fb..234a4ebe1 100644
> --- a/lib/netdev-vport.c
> +++ b/lib/netdev-vport.c
> @@ -702,7 +702,9 @@ set_tunnel_config(struct netdev *dev_, const struct smap
> *args, char **errp)
> tnl_cfg.dst_port = htons(atoi(node->value));
> } else if (!strcmp(node->key, "csum") && has_csum) {
> if (!strcmp(node->value, "true")) {
> - tnl_cfg.csum = true;
> + tnl_cfg.csum = NETDEV_TNL_CSUM_ENABLED;
> + } else if (!strcmp(node->value, "false")) {
> + tnl_cfg.csum = NETDEV_TNL_CSUM_DISABLED;
> }
> } else if (!strcmp(node->key, "seq") && has_seq) {
> if (!strcmp(node->value, "true")) {
> @@ -850,6 +852,15 @@ set_tunnel_config(struct netdev *dev_, const struct smap
> *args, char **errp)
> }
> }
>
> + /* The default csum state for GRE is special as it does have an optional
> + * checksum but the default configuration isn't correlated with IP
> version
> + * like UDP tunnels are. Likewise, tunnels with no checksum at all must
> be
> + * in this state. */
> + if (tnl_cfg.csum == NETDEV_TNL_CSUM_DEFAULT &&
> + (!has_csum || strstr(type, "gre"))) {
> + tnl_cfg.csum = NETDEV_TNL_DEFAULT_NO_CSUM;
> + }
> +
> enum tunnel_layers layers = tunnel_supported_layers(type, &tnl_cfg);
> const char *full_type = (strcmp(type, "vxlan") ? type
> : (tnl_cfg.exts & (1 << OVS_VXLAN_EXT_GPE)
> @@ -1026,8 +1037,10 @@ get_tunnel_config(const struct netdev *dev, struct
> smap *args)
> }
> }
>
> - if (tnl_cfg->csum) {
> + if (tnl_cfg->csum == NETDEV_TNL_CSUM_ENABLED) {
> smap_add(args, "csum", "true");
> + } else if (tnl_cfg->csum == NETDEV_TNL_CSUM_DISABLED) {
> + smap_add(args, "csum", "false");
> }
>
> if (tnl_cfg->set_seq) {
> diff --git a/lib/netdev.h b/lib/netdev.h
> index 67a8486bd..5d253157c 100644
> --- a/lib/netdev.h
> +++ b/lib/netdev.h
> @@ -111,6 +111,22 @@ enum netdev_srv6_flowlabel {
> SRV6_FLOWLABEL_COMPUTE,
> };
>
> +enum netdev_tnl_csum {
> + /* Default value for UDP tunnels if no configurations is present.
> Enforce
> + * checksum calculation in IPv6 tunnels, disable in IPv4 tunnels. */
> + NETDEV_TNL_CSUM_DEFAULT = 0,
> +
> + /* Checksum explicitly to be calculated. */
> + NETDEV_TNL_CSUM_ENABLED,
> +
> + /* Checksum calculation explicitly disabled. */
> + NETDEV_TNL_CSUM_DISABLED,
> +
> + /* A value for when there is no checksum or the default value is no
> + * checksum reguardless of IP version. */
* regardless
> + NETDEV_TNL_DEFAULT_NO_CSUM,
> +};
> +
> /* Configuration specific to tunnels. */
> struct netdev_tunnel_config {
> ovs_be64 in_key;
> @@ -139,7 +155,7 @@ struct netdev_tunnel_config {
> uint8_t tos;
> bool tos_inherit;
>
> - bool csum;
> + enum netdev_tnl_csum csum;
> bool dont_fragment;
> enum netdev_pt_mode pt_mode;
>
> diff --git a/ofproto/tunnel.c b/ofproto/tunnel.c
> index 80ddee78a..f067a6c26 100644
> --- a/ofproto/tunnel.c
> +++ b/ofproto/tunnel.c
> @@ -465,9 +465,13 @@ tnl_port_send(const struct ofport_dpif *ofport, struct
> flow *flow,
>
> flow->tunnel.flags &= ~(FLOW_TNL_F_MASK & ~FLOW_TNL_PUB_F_MASK);
> flow->tunnel.flags |= (cfg->dont_fragment ? FLOW_TNL_F_DONT_FRAGMENT : 0)
> - | (cfg->csum ? FLOW_TNL_F_CSUM : 0)
> | (cfg->out_key_present ? FLOW_TNL_F_KEY : 0);
>
> + if (cfg->csum == NETDEV_TNL_CSUM_ENABLED ||
> + (cfg->csum == NETDEV_TNL_CSUM_DEFAULT && !flow->tunnel.ip_dst)) {
> + flow->tunnel.flags |= FLOW_TNL_F_CSUM;
> + }
> +
> if (cfg->set_egress_pkt_mark) {
> flow->pkt_mark = cfg->egress_pkt_mark;
> wc->masks.pkt_mark = UINT32_MAX;
> @@ -706,8 +710,10 @@ tnl_port_format(const struct tnl_port *tnl_port, struct
> ds *ds)
> ds_put_cstr(ds, ", df=false");
> }
>
> - if (cfg->csum) {
> + if (cfg->csum == NETDEV_TNL_CSUM_ENABLED) {
> ds_put_cstr(ds, ", csum=true");
> + } else if (cfg->csum == NETDEV_TNL_CSUM_DISABLED) {
> + ds_put_cstr(ds, ", csum=false");
> }
>
> ds_put_cstr(ds, ")\n");
> diff --git a/tests/tunnel-push-pop-ipv6.at b/tests/tunnel-push-pop-ipv6.at
> index 3f2cf8429..394bdc81c 100644
> --- a/tests/tunnel-push-pop-ipv6.at
> +++ b/tests/tunnel-push-pop-ipv6.at
> @@ -610,6 +610,15 @@ AT_CHECK([ovs-appctl tnl/arp/show | tail -n+3 | sort],
> [0], [dnl
> 2001:cafe::93 f8:bc:12:44:34:b7 br0
> ])
>
> +dnl Disable checksum from VXLAN port.
> +AT_CHECK([ovs-vsctl set Interface t3 options:csum=false])
> +AT_CHECK([ovs-ofctl del-flows int-br])
> +AT_CHECK([ovs-ofctl add-flow int-br action=4])
> +AT_CHECK([ovs-appctl ofproto/trace ovs-dummy
> 'in_port(2),eth(src=36:b1:ee:7c:01:01,dst=36:b1:ee:7c:01:02),eth_type(0x0800),ipv4(src=1.1.3.88,dst=1.1.3.112,proto=47,tos=0,ttl=64,frag=no)'],
> [0], [stdout])
> +AT_CHECK([tail -1 stdout], [0],
> + [Datapath actions:
> tnl_push(tnl_port(4789),header(size=70,type=4,eth(dst=f8:bc:12:44:34:b7,src=aa:55:aa:55:00:00,dl_type=0x86dd),ipv6(src=2001:cafe::88,dst=2001:cafe::93,label=0,proto=17,tclass=0x0,hlimit=64),udp(src=0,dst=4789,csum=0x0),vxlan(flags=0x8000000,vni=0x0)),out_port(100)),1
> +])
> +
> ovs-appctl time/warp 10000
>
> AT_CHECK([ovs-vsctl del-port int-br t3 \
> diff --git a/tests/tunnel-push-pop.at b/tests/tunnel-push-pop.at
> index 97405636f..d571e60c5 100644
> --- a/tests/tunnel-push-pop.at
> +++ b/tests/tunnel-push-pop.at
> @@ -642,6 +642,13 @@ AT_CHECK([tail -1 stdout], [0],
> [Datapath actions:
> tnl_push(tnl_port(4789),header(size=50,type=4,eth(dst=f8:bc:12:44:34:b6,src=aa:55:aa:55:00:00,dl_type=0x0800),ipv4(src=1.1.2.88,dst=1.1.2.92,proto=17,tos=0,ttl=64,frag=0x4000),udp(src=0,dst=4789,csum=0x0),vxlan(flags=0x8000000,vni=0x7b)),out_port(100)),1
> ])
>
> +dnl Check VXLAN tunnel push with checksum.
> +AT_CHECK([ovs-vsctl set Interface t2 options:csum=true])
> +AT_CHECK([ovs-appctl ofproto/trace ovs-dummy
> 'in_port(2),eth(src=36:b1:ee:7c:01:01,dst=36:b1:ee:7c:01:02),eth_type(0x0800),ipv4(src=1.1.3.88,dst=1.1.3.112,proto=47,tos=0,ttl=64,frag=no)'],
> [0], [stdout])
> +AT_CHECK([tail -1 stdout], [0],
> + [Datapath actions:
> tnl_push(tnl_port(4789),header(size=50,type=4,eth(dst=f8:bc:12:44:34:b6,src=aa:55:aa:55:00:00,dl_type=0x0800),ipv4(src=1.1.2.88,dst=1.1.2.92,proto=17,tos=0,ttl=64,frag=0x4000),udp(src=0,dst=4789,csum=0xffff),vxlan(flags=0x8000000,vni=0x7b)),out_port(100)),1
> +])
> +
> AT_CHECK([ovs-appctl tnl/neigh/show | tail -n+3 | sort], [0], [dnl
> 1.1.2.92 f8:bc:12:44:34:b6 br0
> 1.1.2.93 f8:bc:12:44:34:b7 br0
> diff --git a/tests/tunnel.at b/tests/tunnel.at
> index 9d539ee6f..31e935901 100644
> --- a/tests/tunnel.at
> +++ b/tests/tunnel.at
> @@ -1038,7 +1038,7 @@ AT_CHECK([ovs-ofctl add-flows br0 flows.txt])
>
> AT_CHECK([ovs-appctl ofproto/trace ovs-dummy
> 'tunnel(tun_id=0,src=1.1.1.1,dst=1.1.1.2,ttl=64),in_port(4789)'], [0],
> [stdout])
> AT_CHECK([tail -1 stdout], [0],
> - [Datapath actions:
> set(tunnel(ipv6_dst=2001:cafe::1,ttl=64,tp_dst=4789,flags(df))),4789
> + [Datapath actions:
> set(tunnel(ipv6_dst=2001:cafe::1,ttl=64,tp_dst=4789,flags(df|csum))),4789
> ])
Hrm. This change is concerning. Does it mean we actualy had different
defaults for the kernel datapath? i.e. will we start calculating checksums
on IPv6 tunnels in the kernel that we didn't before? A quick look throug
the kernel code suggests so.
Also a fun conversation here:
https://lore.kernel.org/netdev/8d2a6ece65b17ae61343dce27f3709d3cd249832.1455118911.git.pab...@redhat.com/T/#u
The documentaion below seems to be correct with this patch, but it wasn't
correct before... I think, it's fine to change the default behavior for
the kernel datapath, i.e. start calculating checksums for IPv6 tunnels, but
we need to reflect that in the NEWS and the commit message.
>
> AT_CHECK([ovs-appctl ofproto/trace ovs-dummy
> 'tunnel(tun_id=0x0,ipv6_src=2001:cafe::1,ipv6_dst=2001:cafe::2,ttl=64),in_port(4789)'],
> [0], [stdout])
> diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
> index 8a1b607d7..5f309658e 100644
> --- a/vswitchd/vswitch.xml
> +++ b/vswitchd/vswitch.xml
> @@ -3207,9 +3207,15 @@
> <column name="options" key="csum" type='{"type": "boolean"}'>
> <p>
> Optional. Compute encapsulation header (either GRE or UDP)
> - checksums on outgoing packets. Default is disabled, set to
> - <code>true</code> to enable. Checksums present on incoming
> - packets will be validated regardless of this setting.
> + checksums on outgoing packets. When unset (the default value),
> + checksum computing for outgoing packets is enabled for UDP IPv6
> + tunnels, and disabled for GRE and IPv4 UDP tunnels. When set to
> + <code>false</code>, no checksums will be computed for outgoing
> + tunnel encapsulation headers. When <code>true</code>, checksums
> + will be computed for all outgoing tunnel encapsulation headers.
> + Checksums present on incoming packets will be validated
> + regardless of this setting. Incoming packets without a checksum
> + will also be accepted regardless of this setting.
> </p>
>
> <p>
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