From: Ben Pfaff Date: Mon, 31 Jan 2011 23:47:43 +0000 (-0800) Subject: datapath: Fix behavior of NLA_NESTED for pre-2.6.29 kernels. X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0700107651b6a774f8f7ba873259a5d5011e3cb0;p=openvswitch datapath: Fix behavior of NLA_NESTED for pre-2.6.29 kernels. Before v2.6.29, a NLA_NESTED attribute, if it was present, was not allowed to be empty. However, OVS depends on the ability to accept empty attributes. For example, a present but empty ODP_FLOW_ATTR_ACTIONS on ODP_FLOW_CMD_SET replaces the existing set of actions by an empty "drop" action, whereas a missing ODP_FLOW_ATTR_ACTIONS leaves the existing actions, if any, unchanged. NLA_NESTED is different from NLA_UNSPEC in only two ways: * If the size of the nested attributes is zero, no further size checks are performed. * If the size of the nested attributes is not zero and no length parameter is specified the minimum size of nested attributes is NLA_HDRLEN. nla_parse_nested() validates that there is at least enough space for NLA_HDRLEN, so neither of these conditions are important, and we might as well use NLA_UNSPEC with old kernels. Signed-off-by: Ben Pfaff Acked-by: Jesse Gross --- diff --git a/datapath/linux-2.6/compat-2.6/include/net/netlink.h b/datapath/linux-2.6/compat-2.6/include/net/netlink.h index 0f881f1c..aa7c09c0 100644 --- a/datapath/linux-2.6/compat-2.6/include/net/netlink.h +++ b/datapath/linux-2.6/compat-2.6/include/net/netlink.h @@ -4,6 +4,31 @@ #include #include_next +#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,29) +/* Before v2.6.29, a NLA_NESTED attribute, if it was present, was not allowed + * to be empty. However, OVS depends on the ability to accept empty + * attributes. For example, a present but empty ODP_FLOW_ATTR_ACTIONS on + * ODP_FLOW_CMD_SET replaces the existing set of actions by an empty "drop" + * action, whereas a missing ODP_FLOW_ATTR_ACTIONS leaves the existing + * actions, if any, unchanged. + * + * NLA_NESTED is different from NLA_UNSPEC in only two ways: + * + * - If the size of the nested attributes is zero, no further size checks + * are performed. + * + * - If the size of the nested attributes is not zero and no length + * parameter is specified the minimum size of nested attributes is + * NLA_HDRLEN. + * + * nla_parse_nested() validates that there is at least enough space for + * NLA_HDRLEN, so neither of these conditions are important, and we might + * as well use NLA_UNSPEC with old kernels. + */ +#undef NLA_NESTED +#define NLA_NESTED NLA_UNSPEC +#endif + #ifndef HAVE_NLA_NUL_STRING static inline int VERIFY_NUL_STRING(struct nlattr *attr, int maxlen) {