zebra: upon NS creation, collect the NSID via netlink

A NS identifier is collected by netlink. This identifier is a 32 bit
identifier that is either generated by the kernel (if not set) or
manually set by a set netlink command. The commit here is getting the
NSID from the newly created NS. If the linux option to create or get a
new NSID from the kernel does not exist, then the NSID is locally
genrated.

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>

include/linux/net_namespace.h

@@ -0,0 +1,23 @@
+/* Copyright (c) 2015 6WIND S.A.
+ * Author: Nicolas Dichtel <nicolas.dichtel@6wind.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+#ifndef _LINUX_NET_NAMESPACE_H_
+#define _LINUX_NET_NAMESPACE_H_
+
+/* Attributes of RTM_NEWNSID/RTM_GETNSID messages */
+enum {
+	NETNSA_NONE,
+#define NETNSA_NSID_NOT_ASSIGNED -1
+	NETNSA_NSID,
+	NETNSA_PID,
+	NETNSA_FD,
+	__NETNSA_MAX,
+};
+
+#define NETNSA_MAX		(__NETNSA_MAX - 1)
+
+#endif /* _LINUX_NET_NAMESPACE_H_ */

include/subdir.am

@@ -6,4 +6,5 @@ noinst_HEADERS += \
 	include/linux/neighbour.h \
 	include/linux/rtnetlink.h \
 	include/linux/socket.h \
+	include/linux/net_namespace.h \
 	# end

zebra/subdir.am

@@ -65,6 +65,7 @@ zebra_zebra_SOURCES = \
 	zebra/zebra_vty.c \
 	zebra/zebra_vxlan.c \
 	zebra/zserv.c \
+	zebra/zebra_netns_id.c \
 	# end
 
 zebra/zebra_vty_clippy.c: $(CLIPPY_DEPS)
@@ -104,6 +105,7 @@ noinst_HEADERS += \
 	zebra/zebra_vxlan.h \
 	zebra/zebra_vxlan_private.h \
 	zebra/zserv.h \
+	zebra/zebra_netns_id.h \
 	# end
 
 zebra_zebra_irdp_la_SOURCES = \

zebra/zebra_netns_id.c

@@ -0,0 +1,314 @@
+/* zebra NETNS ID handling routines
+ * those routines are implemented locally to avoid having external dependencies.
+ * Copyright (C) 2018 6WIND
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <zebra.h>
+
+#include "ns.h"
+#include "log.h"
+
+#if defined(HAVE_NETLINK)
+
+#include <linux/net_namespace.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+#include "rib.h"
+#include "zebra_ns.h"
+#include "kernel_netlink.h"
+#endif /* defined(HAVE_NETLINK) */
+
+#include "zebra_netns_id.h"
+
+/* in case NEWNSID not available, the NSID will be locally obtained
+ */
+#define NS_BASE_NSID 0
+
+#if defined(HAVE_NETLINK)
+
+#define NETLINK_SOCKET_BUFFER_SIZE 512
+#define NETLINK_ALIGNTO             4
+#define NETLINK_ALIGN(len)          (((len)+NETLINK_ALIGNTO-1)	\
+				     & ~(NETLINK_ALIGNTO-1))
+#define NETLINK_NLATTR_LEN(_a, _b)   (unsigned int)((char *)_a - (char *)_b)
+
+#endif /* defined(HAVE_NETLINK) */
+
+static ns_id_t zebra_ns_id_get_fallback(const char *netnspath)
+{
+	static int zebra_ns_id_local;
+
+	return zebra_ns_id_local++;
+}
+
+#if defined(HAVE_NETLINK)
+
+static struct nlmsghdr *initiate_nlh(char *buf, unsigned int *seq, int type)
+{
+	struct nlmsghdr *nlh;
+
+	nlh = (struct nlmsghdr *)buf;
+	nlh->nlmsg_len = NETLINK_ALIGN(sizeof(struct nlmsghdr));
+
+	nlh->nlmsg_type = type;
+	nlh->nlmsg_flags = NLM_F_REQUEST;
+	if (type == RTM_NEWNSID)
+		nlh->nlmsg_flags |= NLM_F_ACK;
+	nlh->nlmsg_seq = *seq = time(NULL);
+	return nlh;
+}
+
+static int send_receive(int sock, struct nlmsghdr *nlh,
+			unsigned int seq, char *buf)
+{
+	int ret;
+	static const struct sockaddr_nl snl = {
+		.nl_family = AF_NETLINK
+	};
+
+	ret = sendto(sock, (const void *)nlh, (size_t)nlh->nlmsg_len, 0,
+		     (struct sockaddr *) &snl, (socklen_t)sizeof(snl));
+	if (ret < 0) {
+		zlog_err("netlink( %u) sendmsg() error: %s",
+			 sock, safe_strerror(errno));
+		return -1;
+	}
+
+	/* reception */
+	struct sockaddr_nl addr;
+	struct iovec iov = {
+		.iov_base       = buf,
+		.iov_len        = NETLINK_SOCKET_BUFFER_SIZE,
+	};
+	struct msghdr msg = {
+		.msg_name       = &addr,
+		.msg_namelen    = sizeof(struct sockaddr_nl),
+		.msg_iov        = &iov,
+		.msg_iovlen     = 1,
+		.msg_control    = NULL,
+		.msg_controllen = 0,
+		.msg_flags      = 0,
+	};
+	ret = recvmsg(sock, &msg, 0);
+	if (ret < 0) {
+		zlog_err("netlink recvmsg: error %d (errno %u)", ret, errno);
+		return -1;
+	}
+	if (msg.msg_flags & MSG_TRUNC) {
+		zlog_err("netlink recvmsg : error message truncated");
+		return -1;
+	}
+	/* nlh already points to buf */
+	if (nlh->nlmsg_seq != seq) {
+		zlog_err("netlink recvmsg: bad sequence number %x (expected %x)",
+			 seq, nlh->nlmsg_seq);
+		return -1;
+	}
+	return ret;
+}
+
+/* extract on a valid nlmsg the nsid
+ * valid nlmsghdr - not a nlmsgerr
+ */
+static ns_id_t extract_nsid(struct nlmsghdr *nlh, char *buf)
+{
+	ns_id_t ns_id = NS_UNKNOWN;
+	int offset = NETLINK_ALIGN(sizeof(struct nlmsghdr)) +
+		NETLINK_ALIGN(sizeof(struct rtgenmsg));
+	int curr_length = offset;
+	void *tail = (void *)((char *)nlh + NETLINK_ALIGN(nlh->nlmsg_len));
+	struct nlattr *attr;
+
+	for (attr = (struct nlattr *)((char *)buf + offset);
+	     NETLINK_NLATTR_LEN(tail, attr) >= sizeof(struct nlattr) &&
+		     attr->nla_len >= sizeof(struct nlattr) &&
+		     attr->nla_len <= NETLINK_NLATTR_LEN(tail, attr);
+	     attr += NETLINK_ALIGN(attr->nla_len)) {
+		curr_length += attr->nla_len;
+		if ((attr->nla_type & NLA_TYPE_MASK) == NETNSA_NSID) {
+			u_int32_t *ptr = (u_int32_t *)(attr);
+
+			ns_id = ptr[1];
+			break;
+		}
+	}
+	return ns_id;
+}
+
+ns_id_t zebra_ns_id_get(const char *netnspath)
+{
+	int ns_id = -1;
+	struct sockaddr_nl snl;
+	int fd, sock, ret;
+	unsigned int seq;
+	ns_id_t return_nsid = NS_UNKNOWN;
+
+	/* netns path check */
+	if (!netnspath)
+		return NS_UNKNOWN;
+	fd = open(netnspath, O_RDONLY);
+	if (fd == -1)
+		return NS_UNKNOWN;
+
+	/* netlink socket */
+	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+	if (sock < 0) {
+		zlog_err("netlink( %u) socket() error: %s",
+			 sock, safe_strerror(errno));
+		return NS_UNKNOWN;
+	}
+	memset(&snl, 0, sizeof(snl));
+	snl.nl_family = AF_NETLINK;
+	snl.nl_groups = RTNLGRP_NSID;
+	snl.nl_pid = 0; /* AUTO PID */
+	ret = bind(sock, (struct sockaddr *)&snl, sizeof(snl));
+	if (ret < 0) {
+		zlog_err("netlink( %u) socket() bind error: %s",
+			 sock, safe_strerror(errno));
+		close(sock);
+		close(fd);
+		return NS_UNKNOWN;
+	}
+
+	/* message to send to netlink,and response : NEWNSID */
+	char buf[NETLINK_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	struct rtgenmsg *rt;
+	int len;
+
+	memset(buf, 0, NETLINK_SOCKET_BUFFER_SIZE);
+	nlh = initiate_nlh(buf, &seq, RTM_NEWNSID);
+	rt = (struct rtgenmsg *)(buf + nlh->nlmsg_len);
+	nlh->nlmsg_len += NETLINK_ALIGN(sizeof(struct rtgenmsg));
+	rt->rtgen_family = AF_UNSPEC;
+
+	addattr32(nlh, NETLINK_SOCKET_BUFFER_SIZE, NETNSA_FD, fd);
+	addattr32(nlh, NETLINK_SOCKET_BUFFER_SIZE, NETNSA_NSID, ns_id);
+
+	ret = send_receive(sock, nlh, seq, buf);
+	if (ret < 0) {
+		close(sock);
+		close(fd);
+		return NS_UNKNOWN;
+	}
+	nlh = (struct nlmsghdr *)buf;
+
+	/* message to analyse : NEWNSID response */
+	len = ret;
+	ret = 0;
+	do {
+		if (nlh->nlmsg_type >= NLMSG_MIN_TYPE) {
+			return_nsid = extract_nsid(nlh, buf);
+			if (return_nsid != NS_UNKNOWN)
+				break;
+		} else {
+			if (nlh->nlmsg_type == NLMSG_ERROR) {
+				struct nlmsgerr *err = (struct nlmsgerr *)
+					((char *)nlh +
+					 NETLINK_ALIGN(sizeof(
+						struct nlmsghdr)));
+
+				ret = -1;
+				if (err->error < 0)
+					errno = -err->error;
+				else
+					errno = err->error;
+				if (errno == 0) {
+					/* request NEWNSID was successfull
+					 * return EEXIST error to get GETNSID
+					 */
+					errno = EEXIST;
+				}
+			} else {
+				/* other errors ignored
+				 * attempt to get nsid
+				 */
+				ret = -1;
+				errno = EEXIST;
+				break;
+			}
+		}
+		len = len - NETLINK_ALIGN(nlh->nlmsg_len);
+		nlh = (struct nlmsghdr *)((char *)nlh +
+					  NETLINK_ALIGN(nlh->nlmsg_len));
+	} while (len != 0 && return_nsid != NS_UNKNOWN && ret == 0);
+
+	if (ret <= 0) {
+		if (errno != EEXIST && ret != 0) {
+			zlog_err("netlink( %u) recvfrom() error 2 when reading: %s",
+				 fd, safe_strerror(errno));
+			close(sock);
+			close(fd);
+			if (errno == ENOTSUP) {
+				zlog_warn("NEWNSID locally generated");
+				return zebra_ns_id_get_fallback(netnspath);
+			}
+			return NS_UNKNOWN;
+		}
+		/* message to send to netlink : GETNSID */
+		memset(buf, 0, NETLINK_SOCKET_BUFFER_SIZE);
+		nlh = initiate_nlh(buf, &seq, RTM_GETNSID);
+		rt = (struct rtgenmsg *)(buf + nlh->nlmsg_len);
+		nlh->nlmsg_len += NETLINK_ALIGN(sizeof(struct rtgenmsg));
+		rt->rtgen_family = AF_UNSPEC;
+
+		addattr32(nlh, NETLINK_SOCKET_BUFFER_SIZE, NETNSA_FD, fd);
+		addattr32(nlh, NETLINK_SOCKET_BUFFER_SIZE, NETNSA_NSID, ns_id);
+
+		ret = send_receive(sock, nlh, seq, buf);
+		if (ret < 0) {
+			close(sock);
+			close(fd);
+			return NS_UNKNOWN;
+		}
+		nlh = (struct nlmsghdr *)buf;
+		len = ret;
+		ret = 0;
+		do {
+			if (nlh->nlmsg_type >= NLMSG_MIN_TYPE) {
+				return_nsid = extract_nsid(nlh, buf);
+				if (return_nsid != NS_UNKNOWN)
+					break;
+			} else if (nlh->nlmsg_type == NLMSG_ERROR) {
+				struct nlmsgerr *err = (struct nlmsgerr *)
+					((char *)nlh +
+					 NETLINK_ALIGN(sizeof(
+						 struct nlmsghdr)));
+				if (err->error < 0)
+					errno = -err->error;
+				else
+					errno = err->error;
+				break;
+			}
+			len = len - NETLINK_ALIGN(nlh->nlmsg_len);
+			nlh = (struct nlmsghdr *)((char *)nlh +
+				  NETLINK_ALIGN(nlh->nlmsg_len));
+		} while (len != 0 && return_nsid != NS_UNKNOWN && ret == 0);
+	}
+
+	close(fd);
+	close(sock);
+	return return_nsid;
+}
+
+#else
+ns_id_t zebra_ns_id_get(const char *netnspath)
+{
+	return zebra_ns_id_get_fallback(netnspath);
+}
+#endif /* ! defined(HAVE_NETLINK) */

zebra/zebra_netns_id.h

@@ -0,0 +1,25 @@
+/* zebra NETNS ID handling routines
+ * Copyright (C) 2018 6WIND
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#if !defined(__ZEBRA_NS_ID_H__)
+#define __ZEBRA_NS_ID_H__
+#include "zebra.h"
+#include "ns.h"
+
+extern ns_id_t zebra_ns_id_get(const char *netnspath);
+
+#endif /* __ZEBRA_NS_ID_H__ */