tools/bpf: add more netlink functionalities in lib/bpf

This patch added a few netlink attribute parsing functions
and the netlink API functions to query networking links, tc classes,
tc qdiscs and tc filters. For example, the following API is
to get networking links:
  int nl_get_link(int sock, unsigned int nl_pid,
                  dump_nlmsg_t dump_link_nlmsg,
                  void *cookie);

Note that when the API is called, the user also provided a
callback function with the following signature:
  int (*dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);

The "cookie" is the parameter the user passed to the API and will
be available for the callback function.
The "msg" is the information about the result, e.g., ifinfomsg or
tcmsg. The "tb" is the parsed netlink attributes.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 96c55fac54c3..e3b00e23e181 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -46,6 +46,7 @@ enum libbpf_errno {
 	LIBBPF_ERRNO__PROGTYPE,	/* Kernel doesn't support this program type */
 	LIBBPF_ERRNO__WRNGPID,	/* Wrong pid in netlink message */
 	LIBBPF_ERRNO__INVSEQ,	/* Invalid netlink sequence */
+	LIBBPF_ERRNO__NLPARSE,	/* netlink parsing error */
 	__LIBBPF_ERRNO__END,
 };
 
@@ -297,4 +298,19 @@ int bpf_perf_event_read_simple(void *mem, unsigned long size,
 			       unsigned long page_size,
 			       void **buf, size_t *buf_len,
 			       bpf_perf_event_print_t fn, void *priv);
+
+struct nlmsghdr;
+struct nlattr;
+typedef int (*dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
+typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, dump_nlmsg_t,
+			      void *cookie);
+int bpf_netlink_open(unsigned int *nl_pid);
+int nl_get_link(int sock, unsigned int nl_pid, dump_nlmsg_t dump_link_nlmsg,
+		void *cookie);
+int nl_get_class(int sock, unsigned int nl_pid, int ifindex,
+		 dump_nlmsg_t dump_class_nlmsg, void *cookie);
+int nl_get_qdisc(int sock, unsigned int nl_pid, int ifindex,
+		 dump_nlmsg_t dump_qdisc_nlmsg, void *cookie);
+int nl_get_filter(int sock, unsigned int nl_pid, int ifindex, int handle,
+		  dump_nlmsg_t dump_filter_nlmsg, void *cookie);
 #endif