From afdc3238ec948531205f5c5f77d2de7bae519c71 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Mon, 25 Jun 2007 14:30:16 -0700 Subject: [PATCH] [RTNETLINK]: Add nested compat attribute Add a nested compat attribute type that can be used to convert attributes that contain a structure to nested attributes in a backwards compatible way. The attribute looks like this: struct { [ compat contents ] struct rtattr { .rta_len = total size, .rta_type = type, } rta; struct old_structure struct; [ nested top-level attribute ] struct rtattr { .rta_len = nest size, .rta_type = type, } nest_attr; [ optional 0 .. n nested attributes ] struct rtattr { .rta_len = private attribute len, .rta_type = private attribute typ, } nested_attr; struct nested_data data; }; Since both userspace and kernel deal correctly with attributes that are larger than expected old versions will just parse the compat part and ignore the rest. Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- include/linux/rtnetlink.h | 14 ++++++++++++++ net/core/rtnetlink.c | 16 ++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h index 6127858485..6731e7f4cc 100644 --- a/include/linux/rtnetlink.h +++ b/include/linux/rtnetlink.h @@ -570,6 +570,8 @@ static __inline__ int rtattr_strcmp(const struct rtattr *rta, const char *str) } extern int rtattr_parse(struct rtattr *tb[], int maxattr, struct rtattr *rta, int len); +extern int rtattr_parse_nested_compat(struct rtattr *tb[], int maxattr, + struct rtattr *rta, void **data, int len); #define rtattr_parse_nested(tb, max, rta) \ rtattr_parse((tb), (max), RTA_DATA((rta)), RTA_PAYLOAD((rta))) @@ -638,6 +640,18 @@ extern void __rta_fill(struct sk_buff *skb, int attrtype, int attrlen, const voi ({ (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \ (skb)->len; }) +#define RTA_NEST_COMPAT(skb, type, attrlen, data) \ +({ struct rtattr *__start = (struct rtattr *)skb_tail_pointer(skb); \ + RTA_PUT(skb, type, attrlen, data); \ + RTA_NEST(skb, type); \ + __start; }) + +#define RTA_NEST_COMPAT_END(skb, start) \ +({ struct rtattr *__nest = (void *)(start) + NLMSG_ALIGN((start)->rta_len); \ + (start)->rta_len = skb_tail_pointer(skb) - (unsigned char *)(start); \ + RTA_NEST_END(skb, __nest); \ + (skb)->len; }) + #define RTA_NEST_CANCEL(skb, start) \ ({ if (start) \ skb_trim(skb, (unsigned char *) (start) - (skb)->data); \ diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 06c0c5afab..c25d23ba6d 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -97,6 +97,21 @@ int rtattr_parse(struct rtattr *tb[], int maxattr, struct rtattr *rta, int len) return 0; } +int rtattr_parse_nested_compat(struct rtattr *tb[], int maxattr, + struct rtattr *rta, void **data, int len) +{ + if (RTA_PAYLOAD(rta) < len) + return -1; + *data = RTA_DATA(rta); + + if (RTA_PAYLOAD(rta) >= RTA_ALIGN(len) + sizeof(struct rtattr)) { + rta = RTA_DATA(rta) + RTA_ALIGN(len); + return rtattr_parse_nested(tb, maxattr, rta); + } + memset(tb, 0, sizeof(struct rtattr *) * maxattr); + return 0; +} + static struct rtnl_link *rtnl_msg_handlers[NPROTO]; static inline int rtm_msgindex(int msgtype) @@ -1297,6 +1312,7 @@ void __init rtnetlink_init(void) EXPORT_SYMBOL(__rta_fill); EXPORT_SYMBOL(rtattr_strlcpy); EXPORT_SYMBOL(rtattr_parse); +EXPORT_SYMBOL(rtattr_parse_nested_compat); EXPORT_SYMBOL(rtnetlink_put_metrics); EXPORT_SYMBOL(rtnl_lock); EXPORT_SYMBOL(rtnl_trylock); -- 2.39.5