[ovs-dev] [QoS v2 13/17] netlink: Improve support for nested Netlink attributes.
Ben Pfaff
blp at nicira.com
Tue Jun 8 20:41:33 UTC 2010
Fairly often it happens that nested Netlink attributes must themselves
contain Netlink attributes. In such a case, nlmsg_put_nested() is not so
convenient, because it requires the contents to be pre-assembled and then
copied into place. This commit introduces a new interface that instead
allows the nested attributes to be assembled in-place. As a demonstration,
it updates nl_msg_put_nested() to use this new interface.
---
lib/netlink.c | 34 ++++++++++++++++++++++++++++------
lib/netlink.h | 14 +++++++++-----
2 files changed, 37 insertions(+), 11 deletions(-)
diff --git a/lib/netlink.c b/lib/netlink.c
index 6eee028..bde66b3 100644
--- a/lib/netlink.c
+++ b/lib/netlink.c
@@ -811,15 +811,37 @@ nl_msg_put_string(struct ofpbuf *msg, uint16_t type, const char *value)
nl_msg_put_unspec(msg, type, value, strlen(value) + 1);
}
-/* Appends a Netlink attribute of the given 'type' and the given buffered
- * netlink message in 'nested_msg' to 'msg'. The nlmsg_len field in
- * 'nested_msg' is finalized to match 'nested_msg->size'. */
+/* Adds the header for nested Netlink attributes to 'msg', with the specified
+ * 'type', and returns the header's offset within 'msg'. The caller should add
+ * the content for the nested Netlink attribute to 'msg' (e.g. using the other
+ * nl_msg_*() functions), and then pass the returned offset to
+ * nl_msg_end_nested() to finish up the nested attributes. */
+size_t
+nl_msg_start_nested(struct ofpbuf *msg, uint16_t type)
+{
+ size_t offset = msg->size;
+ nl_msg_put_unspec(msg, type, NULL, 0);
+ return offset;
+}
+
+/* Finalizes a nested Netlink attribute in 'msg'. 'offset' should be the value
+ * returned by nl_msg_start_nested(). */
+void
+nl_msg_end_nested(struct ofpbuf *msg, size_t offset)
+{
+ struct nlattr *attr = ofpbuf_at_assert(msg, offset, sizeof *attr);
+ attr->nla_len = msg->size - offset;
+}
+
+/* Appends a nested Netlink attribute of the given 'type', with the 'size'
+ * bytes of content starting at 'data', to 'msg'. */
void
nl_msg_put_nested(struct ofpbuf *msg,
- uint16_t type, struct ofpbuf *nested_msg)
+ uint16_t type, const void *data, size_t size)
{
- nl_msg_nlmsghdr(nested_msg)->nlmsg_len = nested_msg->size;
- nl_msg_put_unspec(msg, type, nested_msg->data, nested_msg->size);
+ size_t offset = nl_msg_start_nested(msg, type);
+ nl_msg_put(msg, data, size);
+ nl_msg_end_nested(msg, offset);
}
/* If 'buffer' begins with a valid "struct nlmsghdr", pulls the header and its
diff --git a/lib/netlink.h b/lib/netlink.h
index 13f1459..9cb1f81 100644
--- a/lib/netlink.h
+++ b/lib/netlink.h
@@ -52,10 +52,10 @@ void nl_sock_wait(const struct nl_sock *, short int events);
/* Table dumping. */
struct nl_dump {
- uint32_t seq;
- struct nl_sock *sock;
- int status;
- struct ofpbuf *buffer;
+ struct nl_sock *sock; /* Socket being dumped. */
+ uint32_t seq; /* Expected nlmsg_seq for replies. */
+ struct ofpbuf *buffer; /* Receive buffer currently being iterated. */
+ int status; /* 0=OK, EOF=done, or positive errno value. */
};
void nl_dump_start(struct nl_dump *, struct nl_sock *,
@@ -89,7 +89,11 @@ void nl_msg_put_u16(struct ofpbuf *, uint16_t type, uint16_t value);
void nl_msg_put_u32(struct ofpbuf *, uint16_t type, uint32_t value);
void nl_msg_put_u64(struct ofpbuf *, uint16_t type, uint64_t value);
void nl_msg_put_string(struct ofpbuf *, uint16_t type, const char *value);
-void nl_msg_put_nested(struct ofpbuf *, uint16_t type, struct ofpbuf *);
+
+size_t nl_msg_start_nested(struct ofpbuf *, uint16_t type);
+void nl_msg_end_nested(struct ofpbuf *, size_t offset);
+void nl_msg_put_nested(struct ofpbuf *, uint16_t type,
+ const void *data, size_t size);
/* Separating buffers into individual messages. */
struct nlmsghdr *nl_msg_next(struct ofpbuf *buffer, struct ofpbuf *msg);
--
1.7.1
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