Older kernels do not reject unsupported features. This can lead to a situation in which 'ovs-vswitchd' believes that a feature is supported when, in fact, it is not.
This patch probes for this by attempting to set a known unsupported feature. Reported-by: Dumitru Ceara <dce...@redhat.com> Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=2004083 Suggested-by: Ilya Maximets <i.maxim...@ovn.org> Signed-off-by: Mark Gray <mark.d.g...@redhat.com> --- lib/dpif-netlink.c | 66 ++++++++++++++++++++++++++++++---------------- 1 file changed, 43 insertions(+), 23 deletions(-) diff --git a/lib/dpif-netlink.c b/lib/dpif-netlink.c index 34fc04237333..c16323f7ee21 100644 --- a/lib/dpif-netlink.c +++ b/lib/dpif-netlink.c @@ -84,6 +84,8 @@ enum { MAX_PORTS = USHRT_MAX }; #define EPOLLEXCLUSIVE (1u << 28) #endif +#define OVS_DP_F_UNSUPPORTED (1 << 31); + /* This PID is not used by the kernel datapath when using dispatch per CPU, * but it is required to be set (not zero). */ #define DPIF_NETLINK_PER_CPU_PID UINT32_MAX @@ -382,36 +384,54 @@ dpif_netlink_open(const struct dpif_class *class OVS_UNUSED, const char *name, dp_request.cmd = OVS_DP_CMD_SET; } - /* The Open vSwitch kernel module has two modes for dispatching upcalls: - * per-vport and per-cpu. - * - * When dispatching upcalls per-vport, the kernel will - * send the upcall via a Netlink socket that has been selected based on the - * vport that received the packet that is causing the upcall. - * - * When dispatching upcall per-cpu, the kernel will send the upcall via - * a Netlink socket that has been selected based on the cpu that received - * the packet that is causing the upcall. - * - * First we test to see if the kernel module supports per-cpu dispatching - * (the preferred method). If it does not support per-cpu dispatching, we - * fall back to the per-vport dispatch mode. + /* Some older kernels will not reject unknown features. This will cause + * 'ovs-vswitchd' to incorrectly assume a feature is supported. In order to + * test for that, we attempt to set a feature that we know is not supported + * by any kernel. If this feature is not rejected, we can assume we are + * running on one of these older kernels. */ dp_request.user_features |= OVS_DP_F_UNALIGNED; - dp_request.user_features &= ~OVS_DP_F_VPORT_PIDS; - dp_request.user_features |= OVS_DP_F_DISPATCH_UPCALL_PER_CPU; + dp_request.user_features |= OVS_DP_F_VPORT_PIDS; + dp_request.user_features |= OVS_DP_F_UNSUPPORTED; error = dpif_netlink_dp_transact(&dp_request, &dp, &buf); + dp_request.user_features &= ~OVS_DP_F_UNSUPPORTED; if (error) { - dp_request.user_features &= ~OVS_DP_F_DISPATCH_UPCALL_PER_CPU; - dp_request.user_features |= OVS_DP_F_VPORT_PIDS; + /* The Open vSwitch kernel module has two modes for dispatching + * upcalls: per-vport and per-cpu. + * + * When dispatching upcalls per-vport, the kernel will + * send the upcall via a Netlink socket that has been selected based on + * the vport that received the packet that is causing the upcall. + * + * When dispatching upcall per-cpu, the kernel will send the upcall via + * a Netlink socket that has been selected based on the cpu that + * received the packet that is causing the upcall. + * + * First we test to see if the kernel module supports per-cpu + * dispatching (the preferred method). If it does not support per-cpu + * dispatching, we fall back to the per-vport dispatch mode. + */ + dp_request.user_features |= OVS_DP_F_UNALIGNED; + dp_request.user_features &= ~OVS_DP_F_VPORT_PIDS; + dp_request.user_features |= OVS_DP_F_DISPATCH_UPCALL_PER_CPU; error = dpif_netlink_dp_transact(&dp_request, &dp, &buf); - } - if (error) { - return error; + if (error) { + dp_request.user_features &= ~OVS_DP_F_DISPATCH_UPCALL_PER_CPU; + dp_request.user_features |= OVS_DP_F_VPORT_PIDS; + error = dpif_netlink_dp_transact(&dp_request, &dp, &buf); + } + if (error) { + return error; + } + + error = open_dpif(&dp, dpifp); + dpif_netlink_set_features(*dpifp, OVS_DP_F_TC_RECIRC_SHARING); + } else { + VLOG_INFO("Kernel does not correctly support feature negotiation. " + "Using standard features"); + error = open_dpif(&dp, dpifp); } - error = open_dpif(&dp, dpifp); - dpif_netlink_set_features(*dpifp, OVS_DP_F_TC_RECIRC_SHARING); ofpbuf_delete(buf); if (create) { -- 2.27.0 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
