add libgtpnl
This patch adds the libgtpnl library. Harald mentioned that he wanted
that the specific code that is added is well encapsulated, so let's
start a small library to interact with the GTP kernel module via netlink
interface.
This was done a bit while in the rush, so the interfaces are not nice
at all and the tools need to be ported on top of this library.
This library will be used to integrate openggsn with the GTP kernel
module.
diff --git a/src/genl.c b/src/genl.c
new file mode 100644
index 0000000..099b317
--- /dev/null
+++ b/src/genl.c
@@ -0,0 +1,146 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <time.h>
+
+#include <libmnl/libmnl.h>
+#include <linux/genetlink.h>
+
+#include <libgtpnl/gtpnl.h>
+
+#include "internal.h"
+
+struct nlmsghdr *
+genl_nlmsg_build_hdr(char *buf, uint16_t type, uint16_t flags, uint32_t seq,
+ uint8_t cmd)
+{
+ struct nlmsghdr *nlh;
+ struct genlmsghdr *genl;
+
+ nlh = mnl_nlmsg_put_header(buf);
+ nlh->nlmsg_type = type;
+ nlh->nlmsg_flags = NLM_F_REQUEST | flags;
+ nlh->nlmsg_seq = seq;
+
+ genl = mnl_nlmsg_put_extra_header(nlh, sizeof(struct genlmsghdr));
+ genl->cmd = cmd;
+ genl->version = 0;
+
+ return nlh;
+}
+EXPORT_SYMBOL(genl_nlmsg_build_hdr);
+
+static int genl_ctrl_validate_cb(const struct nlattr *attr, void *data)
+{
+ const struct nlattr **tb = data;
+ int type = mnl_attr_get_type(attr);
+
+ if (mnl_attr_type_valid(attr, CTRL_ATTR_MAX) < 0)
+ return MNL_CB_OK;
+
+ switch(type) {
+ case CTRL_ATTR_FAMILY_ID:
+ if (mnl_attr_validate(attr, MNL_TYPE_U16) < 0) {
+ perror("mnl_attr_validate");
+ return MNL_CB_ERROR;
+ }
+ break;
+ }
+ tb[type] = attr;
+ return MNL_CB_OK;
+}
+
+static int genl_ctrl_cb(const struct nlmsghdr *nlh, void *data)
+{
+ struct nlattr *tb[CTRL_ATTR_MAX + 1] = {};
+ struct genlmsghdr *genl = mnl_nlmsg_get_payload(nlh);
+ int32_t *genl_id = data;
+
+ mnl_attr_parse(nlh, sizeof(*genl), genl_ctrl_validate_cb, tb);
+ if (tb[CTRL_ATTR_FAMILY_ID])
+ *genl_id = mnl_attr_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
+ else
+ *genl_id = -1;
+
+ return MNL_CB_OK;
+}
+
+struct mnl_socket *genl_socket_open(void)
+{
+ struct mnl_socket *nl;
+
+ nl = mnl_socket_open(NETLINK_GENERIC);
+ if (nl == NULL) {
+ perror("mnl_socket_open");
+ return NULL;
+ }
+
+ if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+ perror("mnl_socket_bind");
+ return NULL;
+ }
+
+ return nl;
+}
+EXPORT_SYMBOL(genl_socket_open);
+
+int genl_socket_talk(struct mnl_socket *nl, struct nlmsghdr *nlh, uint32_t seq,
+ int (*cb)(const struct nlmsghdr *nlh, void *data),
+ void *data)
+{
+ char buf[MNL_SOCKET_BUFFER_SIZE];
+ int ret;
+
+ if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
+ perror("mnl_socket_send");
+ return -1;
+ }
+
+ ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+ while (ret > 0) {
+ ret = mnl_cb_run(buf, ret, seq, mnl_socket_get_portid(nl),
+ cb, data);
+ if (ret <= 0)
+ break;
+ ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL(genl_socket_talk);
+
+static struct nlmsghdr *
+genl_nlmsg_build_lookup(char *buf, const char *subsys_name)
+{
+ struct nlmsghdr *nlh;
+ struct genlmsghdr *genl;
+
+ nlh = mnl_nlmsg_put_header(buf);
+ nlh->nlmsg_type = GENL_ID_CTRL;
+ nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+ nlh->nlmsg_seq = time(NULL);
+
+ genl = mnl_nlmsg_put_extra_header(nlh, sizeof(struct genlmsghdr));
+ genl->cmd = CTRL_CMD_GETFAMILY;
+ genl->version = 1;
+
+ mnl_attr_put_u32(nlh, CTRL_ATTR_FAMILY_ID, GENL_ID_CTRL);
+ mnl_attr_put_strz(nlh, CTRL_ATTR_FAMILY_NAME, subsys_name);
+
+ return nlh;
+}
+
+int genl_lookup_family(struct mnl_socket *nl, const char *family)
+{
+ int32_t genl_id;
+ char buf[MNL_SOCKET_BUFFER_SIZE];
+ struct nlmsghdr *nlh = genl_nlmsg_build_lookup(buf, "gtp");
+ int err;
+
+ err = genl_socket_talk(nl, nlh, nlh->nlmsg_seq, genl_ctrl_cb, &genl_id);
+ if (err < 0)
+ return -1;
+
+ return genl_id;
+}
+EXPORT_SYMBOL(genl_lookup_family);