diff options
Diffstat (limited to 'lib/attr.c')
| -rw-r--r-- | lib/attr.c | 49 |
1 files changed, 49 insertions, 0 deletions
@@ -962,6 +962,55 @@ int nla_nest_end(struct nl_msg *msg, struct nlattr *start) } /** + * Finalize nesting of attributes without stripping off empty attributes. + * @arg msg Netlink message. + * @arg start Container attribute as returned from nla_nest_start(). + * + * Corrects the container attribute header to include the appeneded attributes. + * Keep empty attribute if NO actual attribute payload exists. + * + * @return 0 on success or a negative error code. + */ +int nla_nest_end_keep_empty(struct nl_msg *msg, struct nlattr *start) +{ + size_t pad, len; + + len = (void *) nlmsg_tail(msg->nm_nlh) - (void *) start; + + if (len > USHRT_MAX) { + /* + * Max nlattr size is exceeded, trim the attribute header again + */ + nla_nest_cancel(msg, start); + + /* Return error only if nlattr size was exceeded */ + return -NLE_ATTRSIZE; + } + + start->nla_len = len; + + pad = NLMSG_ALIGN(msg->nm_nlh->nlmsg_len) - msg->nm_nlh->nlmsg_len; + if (pad > 0) { + /* + * Data inside attribute does not end at a alignment boundry. + * Pad accordingly and accoun for the additional space in + * the message. nlmsg_reserve() may never fail in this situation, + * the allocate message buffer must be a multiple of NLMSG_ALIGNTO. + */ + if (!nlmsg_reserve(msg, pad, 0)) + BUG(); + + NL_DBG(2, "msg %p: attr <%p> %d: added %zu bytes of padding\n", + msg, start, start->nla_type, pad); + } + + NL_DBG(2, "msg %p: attr <%p> %d: closing nesting, len=%u\n", + msg, start, start->nla_type, start->nla_len); + + return 0; +} + +/** * Cancel the addition of a nested attribute * @arg msg Netlink message * @arg attr Nested netlink attribute |