There are many unpatched kernel versions out there that do not initialize the reserved fields of struct nexthop_grp. The issue with that is that if those fields were to be used for some end (i.e. stop being reserved), old kernels would still keep sending random data through the field, and a new userspace could not rely on the value. In this patch, use the existing NHA_OP_FLAGS, which is currently inbound only, to carry flags back to the userspace. Add a flag to indicate that the reserved fields in struct nexthop_grp are zeroed before dumping. This is reliant on the actual fix from commit 6d745cd0e972 ("net: nexthop: Initialize all fields in dumped nexthops").
Unified · Split
| @@ -33,6 +33,9 @@ enum { · 32 unmodified lines | ||
| 33 | 33 | #define NHA_OP_FLAG_DUMP_STATS BIT(0) |
| 34 | 34 | #define NHA_OP_FLAG_DUMP_HW_STATS BIT(1) |
| 35 | 35 | |
| 36 | +/* Response OP_FLAGS. */ | |
| 37 | +#define NHA_OP_FLAG_RESP_GRP_RESVD_0 BIT(31) /* Dump clears resvd fields. */ | |
| 38 | + | |
| 36 | 39 | enum { |
| 37 | 40 | NHA_UNSPEC, |
| 38 | 41 | NHA_ID, /* u32; id for nexthop. id == 0 means auto-assign */ |
| @@ -865,7 +865,7 @@ out: · 864 unmodified lines | ||
| 865 | 865 | } |
| 866 | 866 | |
| 867 | 867 | static int nla_put_nh_group(struct sk_buff *skb, struct nexthop *nh, |
| 868 | − u32 op_flags) | |
| 868 | + u32 op_flags, u32 *resp_op_flags) | |
| 869 | 869 | { |
| 870 | 870 | struct nh_group *nhg = rtnl_dereference(nh->nh_grp); |
| 871 | 871 | struct nexthop_grp *p; |
| @@ -874,6 +874,8 @@ static int nla_put_nh_group(struct sk_buff *skb, struct nexthop *nh, · 2 unmodified lines | ||
| 874 | 874 | u16 group_type = 0; |
| 875 | 875 | int i; |
| 876 | 876 | |
| 877 | + *resp_op_flags |= NHA_OP_FLAG_RESP_GRP_RESVD_0; | |
| 878 | + | |
| 877 | 879 | if (nhg->hash_threshold) |
| 878 | 880 | group_type = NEXTHOP_GRP_TYPE_MPATH; |
| 879 | 881 | else if (nhg->resilient) |
| @@ -934,10 +936,12 @@ static int nh_fill_node(struct sk_buff *skb, struct nexthop *nh, · 54 unmodified lines | ||
| 934 | 936 | |
| 935 | 937 | if (nh->is_group) { |
| 936 | 938 | struct nh_group *nhg = rtnl_dereference(nh->nh_grp); |
| 939 | + u32 resp_op_flags = 0; | |
| 937 | 940 | |
| 938 | 941 | if (nhg->fdb_nh && nla_put_flag(skb, NHA_FDB)) |
| 939 | 942 | goto nla_put_failure; |
| 940 | − if (nla_put_nh_group(skb, nh, op_flags)) | |
| 943 | + if (nla_put_nh_group(skb, nh, op_flags, &resp_op_flags) || | |
| 944 | + nla_put_u32(skb, NHA_OP_FLAGS, resp_op_flags)) | |
| 941 | 945 | goto nla_put_failure; |
| 942 | 946 | goto out; |
| 943 | 947 | } |
| @@ -1050,7 +1054,9 @@ static size_t nh_nlmsg_size(struct nexthop *nh) · 106 unmodified lines | ||
| 1050 | 1054 | sz += nla_total_size(4); /* NHA_ID */ |
| 1051 | 1055 | |
| 1052 | 1056 | if (nh->is_group) |
| 1053 | − sz += nh_nlmsg_size_grp(nh); | |
| 1057 | + sz += nh_nlmsg_size_grp(nh) + | |
| 1058 | + nla_total_size(4) + /* NHA_OP_FLAGS */ | |
| 1059 | + 0; | |
| 1054 | 1060 | else |
| 1055 | 1061 | sz += nh_nlmsg_size_single(nh); |
| 1056 | 1062 | |