Merge pull request #2608 from brauner/2018-09-11/netns_get_nsid

src/lxc/macro.h

@@ -27,6 +27,7 @@
 #include <linux/loop.h>
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
+#include <linux/types.h>
 #include <stdint.h>
 #include <string.h>
 #include <sys/mount.h>
@@ -279,6 +280,10 @@ extern int __build_bug_on_failed;
 #define RTM_NEWNSID 88
 #endif
 
+#ifndef RTM_GETNSID
+#define RTM_GETNSID 90
+#endif
+
 #ifndef NLMSG_ERROR
 #define NLMSG_ERROR 0x2
 #endif

src/lxc/network.c

@@ -3171,6 +3171,7 @@ int addattr(struct nlmsghdr *n, size_t maxlen, int type, const void *data, size_
 	int len = RTA_LENGTH(alen);
 	struct rtattr *rta;
 
+	errno = EMSGSIZE;
 	if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen)
 		return -1;
 
@@ -3196,7 +3197,7 @@ enum {
 
 int lxc_netns_set_nsid(int fd)
 {
-	ssize_t ret;
+	int ret;
 	char buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
 		 NLMSG_ALIGN(sizeof(struct rtgenmsg)) +
 		 NLMSG_ALIGN(1024)];
@@ -3204,12 +3205,12 @@ int lxc_netns_set_nsid(int fd)
 	struct nlmsghdr *hdr;
 	struct rtgenmsg *msg;
 	int saved_errno;
-	__s32 ns_id = -1;
-	__u32 netns_fd = fd;
+	const __s32 ns_id = -1;
+	const __u32 netns_fd = fd;
 
 	ret = netlink_open(&nlh, NETLINK_ROUTE);
 	if (ret < 0)
-		return ret;
+		return -1;
 
 	memset(buf, 0, sizeof(buf));
 	hdr = (struct nlmsghdr *)buf;
@@ -3222,15 +3223,99 @@ int lxc_netns_set_nsid(int fd)
 	hdr->nlmsg_seq = RTM_NEWNSID;
 	msg->rtgen_family = AF_UNSPEC;
 
-	addattr(hdr, 1024, __LXC_NETNSA_FD, &netns_fd, sizeof(netns_fd));
-	addattr(hdr, 1024, __LXC_NETNSA_NSID, &ns_id, sizeof(ns_id));
+	ret = addattr(hdr, 1024, __LXC_NETNSA_FD, &netns_fd, sizeof(netns_fd));
+	if (ret < 0)
+		goto on_error;
+
+	ret = addattr(hdr, 1024, __LXC_NETNSA_NSID, &ns_id, sizeof(ns_id));
+	if (ret < 0)
+		goto on_error;
 
 	ret = __netlink_transaction(&nlh, hdr, hdr);
+
+on_error:
+	saved_errno = errno;
+	netlink_close(&nlh);
+	errno = saved_errno;
+
+	return ret;
+}
+
+static int parse_rtattr(struct rtattr *tb[], int max, struct rtattr *rta, int len)
+{
+
+	memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
+
+	while (RTA_OK(rta, len)) {
+		unsigned short type = rta->rta_type;
+
+		if ((type <= max) && (!tb[type]))
+			tb[type] = rta;
+
+		rta = RTA_NEXT(rta, len);
+	}
+
+	return 0;
+}
+
+static inline __s32 rta_getattr_s32(const struct rtattr *rta)
+{
+	return *(__s32 *)RTA_DATA(rta);
+}
+
+#ifndef NETNS_RTA
+#define NETNS_RTA(r) \
+	((struct rtattr *)(((char *)(r)) + NLMSG_ALIGN(sizeof(struct rtgenmsg))))
+#endif
+
+int lxc_netns_get_nsid(int fd)
+{
+	int ret;
+	ssize_t len;
+	char buf[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
+		 NLMSG_ALIGN(sizeof(struct rtgenmsg)) +
+		 NLMSG_ALIGN(1024)];
+	struct rtattr *tb[__LXC_NETNSA_MAX + 1];
+	struct nl_handler nlh;
+	struct nlmsghdr *hdr;
+	struct rtgenmsg *msg;
+	int saved_errno;
+	__u32 netns_fd = fd;
+
+	ret = netlink_open(&nlh, NETLINK_ROUTE);
+	if (ret < 0)
+		return -1;
+
+	memset(buf, 0, sizeof(buf));
+	hdr = (struct nlmsghdr *)buf;
+	msg = (struct rtgenmsg *)NLMSG_DATA(hdr);
+
+	hdr->nlmsg_len = NLMSG_LENGTH(sizeof(*msg));
+	hdr->nlmsg_type = RTM_GETNSID;
+	hdr->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+	hdr->nlmsg_pid = 0;
+	hdr->nlmsg_seq = RTM_GETNSID;
+	msg->rtgen_family = AF_UNSPEC;
+
+	ret = addattr(hdr, 1024, __LXC_NETNSA_FD, &netns_fd, sizeof(netns_fd));
+	if (ret == 0)
+		ret = __netlink_transaction(&nlh, hdr, hdr);
+
 	saved_errno = errno;
 	netlink_close(&nlh);
 	errno = saved_errno;
 	if (ret < 0)
 		return -1;
 
-	return 0;
+	errno = EINVAL;
+	msg = NLMSG_DATA(hdr);
+	len = hdr->nlmsg_len - NLMSG_SPACE(sizeof(*msg));
+	if (len < 0)
+		return -1;
+
+	parse_rtattr(tb, __LXC_NETNSA_MAX, NETNS_RTA(msg), len);
+	if (tb[__LXC_NETNSA_NSID])
+		return rta_getattr_s32(tb[__LXC_NETNSA_NSID]);
+
+	return -1;
 }

src/lxc/network.h

@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <unistd.h>
 #include <arpa/inet.h>
+#include <linux/types.h>
 #include <sys/socket.h>
 
 #include "list.h"
@@ -273,5 +274,6 @@ extern int lxc_network_recv_veth_names_from_parent(struct lxc_handler *handler);
 extern int lxc_network_send_name_and_ifindex_to_parent(struct lxc_handler *handler);
 extern int lxc_network_recv_name_and_ifindex_from_child(struct lxc_handler *handler);
 extern int lxc_netns_set_nsid(int netns_fd);
+extern int lxc_netns_get_nsid(__s32 fd);
 
 #endif /* __LXC_NETWORK_H */