1 files changed, 369 insertions, 0 deletions
diff --git a/zebra/ge_netlink.c b/zebra/ge_netlink.c
new file mode 100644
index 0000000..e7d2e6b
--- /dev/null
+++ b/zebra/ge_netlink.c
@@ -0,0 +1,369 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Generic Netlink functions.
+ * Copyright (C) 2022, Carmine Scarpitta
+ */
+
+#include <zebra.h>
+
+#ifdef HAVE_NETLINK
+
+/* The following definition is to workaround an issue in the Linux kernel
+ * header files with redefinition of 'struct in6_addr' in both
+ * netinet/in.h and linux/in6.h.
+ * Reference - https://sourceware.org/ml/libc-alpha/2013-01/msg00599.html
+ */
+#define _LINUX_IN6_H
+
+#include <linux/genetlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/seg6_genl.h>
+
+#include "lib/ns.h"
+#include "zebra/ge_netlink.h"
+#include "zebra/debug.h"
+#include "zebra/kernel_netlink.h"
+#include "zebra/zebra_router.h"
+#include "zebra/zebra_srv6.h"
+
+
+/**
+ * This file provides an implementation of the functionality exposed by the
+ * kernel through the Generic Netlink mechanism.
+ *
+ * Supported features include the ability to configure the source address used
+ * for SRv6 encapsulation ('sr tunsrc' in kernel terminology).
+ *
+ * At the time of writing this code, the kernel does not send us any asynchronous
+ * notifications when someone changes the 'sr tunsrc' under us. As a result, we
+ * are currently unable to detect when the source address changes and update the
+ * SRv6 encapsulation source address configured in zebra.
+ *
+ * In the future, when the kernel supports async notifications, the implementation
+ * can be improved by listening on the Generic Netlink socket and adding a handler
+ * to process/parse incoming 'sr tunsrc' change messages and update the SRv6 zebra
+ * configuration with the new encap source address.
+ */
+
+
+/*
+ * Numeric family identifier used to configure SRv6 internal parameters through Generic Netlink.
+ */
+static int16_t seg6_genl_family = -1;
+
+static int genl_parse_getfamily(struct nlmsghdr *h, ns_id_t ns_id, int startup)
+{
+	int len;
+	struct rtattr *tb[CTRL_ATTR_MAX + 1];
+	struct genlmsghdr *ghdr = NLMSG_DATA(h);
+	struct rtattr *attrs;
+	const char *family;
+
+	if (h->nlmsg_type != GENL_ID_CTRL) {
+		zlog_err(
+			"Not a controller message, nlmsg_len=%d nlmsg_type=0x%x",
+			h->nlmsg_len, h->nlmsg_type);
+		return 0;
+	}
+
+	len = h->nlmsg_len - NLMSG_LENGTH(GENL_HDRLEN);
+	if (len < 0) {
+		zlog_err(
+			"Message received from netlink is of a broken size %d %zu",
+			h->nlmsg_len, (size_t)NLMSG_LENGTH(GENL_HDRLEN));
+		return -1;
+	}
+
+	if (ghdr->cmd != CTRL_CMD_NEWFAMILY) {
+		zlog_err("Unknown controller command %d", ghdr->cmd);
+		return -1;
+	}
+
+	attrs = (struct rtattr *)((char *)ghdr + GENL_HDRLEN);
+	netlink_parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
+
+	if (tb[CTRL_ATTR_FAMILY_ID] == NULL) {
+		zlog_err("Missing family id TLV");
+		return -1;
+	}
+
+	if (tb[CTRL_ATTR_FAMILY_NAME] == NULL) {
+		zlog_err("Missing family name TLV");
+		return -1;
+	}
+
+	family = (char *)RTA_DATA(tb[CTRL_ATTR_FAMILY_NAME]);
+
+	if (strmatch(family, "SEG6"))
+		seg6_genl_family =
+			*(int16_t *)RTA_DATA(tb[CTRL_ATTR_FAMILY_ID]);
+	else {
+		if (IS_ZEBRA_DEBUG_KERNEL)
+			zlog_err("Unsupported Generic Netlink family '%s'",
+				 family);
+		return -1;
+	}
+
+	return 0;
+}
+
+int genl_resolve_family(const char *family)
+{
+	struct zebra_ns *zns;
+	struct genl_request req;
+
+	memset(&req, 0, sizeof(req));
+
+	zns = zebra_ns_lookup(NS_DEFAULT);
+
+	req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type = GENL_ID_CTRL;
+
+	req.n.nlmsg_pid = zns->ge_netlink_cmd.snl.nl_pid;
+
+	req.g.cmd = CTRL_CMD_GETFAMILY;
+	req.g.version = 0;
+
+	if (!nl_attr_put(&req.n, sizeof(req), CTRL_ATTR_FAMILY_NAME, family,
+			 strlen(family) + 1))
+		return -1;
+
+	return ge_netlink_talk(genl_parse_getfamily, &req.n, zns, false);
+}
+
+/*
+ * sr tunsrc change via netlink interface, using a dataplane context object
+ *
+ * Returns -1 on failure, 0 when the msg doesn't fit entirely in the buffer
+ * otherwise the number of bytes written to buf.
+ */
+ssize_t netlink_sr_tunsrc_set_msg_encode(int cmd, struct zebra_dplane_ctx *ctx,
+					 void *buf, size_t buflen)
+{
+	struct nlsock *nl;
+	const struct in6_addr *tunsrc_addr;
+	struct genl_request *req = buf;
+
+	if (seg6_genl_family < 0) {
+		zlog_err(
+			"Failed to set SRv6 source address: kernel does not support 'SEG6' Generic Netlink family.");
+		return -1;
+	}
+
+	tunsrc_addr = dplane_ctx_get_srv6_encap_srcaddr(ctx);
+	if (!tunsrc_addr)
+		return -1;
+
+	if (buflen < sizeof(*req))
+		return 0;
+
+	nl = kernel_netlink_nlsock_lookup(dplane_ctx_get_ns_sock(ctx));
+
+	memset(req, 0, sizeof(*req));
+
+	req->n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+	req->n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
+
+	/* Prepare Netlink request to set tunsrc addr */
+	req->n.nlmsg_type = seg6_genl_family;
+	req->n.nlmsg_pid = nl->snl.nl_pid;
+
+	req->g.cmd = cmd;
+	req->g.version = SEG6_GENL_VERSION;
+
+	switch (cmd) {
+	case SEG6_CMD_SET_TUNSRC:
+		if (!nl_attr_put(&req->n, buflen, SEG6_ATTR_DST, tunsrc_addr,
+				 sizeof(struct in6_addr)))
+			return 0;
+		break;
+	default:
+		zlog_err("Unsupported command (%u)", cmd);
+		return -1;
+	}
+
+	return NLMSG_ALIGN(req->n.nlmsg_len);
+}
+
+ssize_t netlink_sr_tunsrc_set_msg_encoder(struct zebra_dplane_ctx *ctx,
+					  void *buf, size_t buflen)
+{
+	enum dplane_op_e op;
+	int cmd = 0;
+
+	op = dplane_ctx_get_op(ctx);
+
+	/* Call to netlink layer based on type of operation */
+	if (op == DPLANE_OP_SRV6_ENCAP_SRCADDR_SET) {
+		/* Validate */
+		if (dplane_ctx_get_srv6_encap_srcaddr(ctx) == NULL) {
+			if (IS_ZEBRA_DEBUG_KERNEL)
+				zlog_debug(
+					"sr tunsrc set failed: SRv6 encap source address not set");
+			return -1;
+		}
+
+		cmd = SEG6_CMD_SET_TUNSRC;
+	} else {
+		/* Invalid op */
+		zlog_err("Context received for kernel sr tunsrc update with incorrect OP code (%u)",
+			 op);
+		return -1;
+	}
+
+	return netlink_sr_tunsrc_set_msg_encode(cmd, ctx, buf, buflen);
+}
+
+enum netlink_msg_status
+netlink_put_sr_tunsrc_set_msg(struct nl_batch *bth, struct zebra_dplane_ctx *ctx)
+{
+	enum dplane_op_e op;
+	struct zebra_ns *zns;
+	struct genl_request req;
+
+	op = dplane_ctx_get_op(ctx);
+	assert(op == DPLANE_OP_SRV6_ENCAP_SRCADDR_SET);
+
+	netlink_sr_tunsrc_set_msg_encoder(ctx, &req, sizeof(req));
+
+	zns = zebra_ns_lookup(dplane_ctx_get_ns_sock(ctx));
+
+	return ge_netlink_talk(netlink_talk_filter, &req.n, zns, false);
+}
+
+/**
+ * netlink_sr_tunsrc_reply_read() - Read in SR tunsrc reply from the kernel
+ *
+ * @h:			Netlink message header
+ * @ns_id:		Namspace id
+ * @startup:	Are we reading under startup conditions?
+ *
+ * Return:	Result status
+ */
+int netlink_sr_tunsrc_reply_read(struct nlmsghdr *h, ns_id_t ns_id, int startup)
+{
+	int len;
+	struct genlmsghdr *ghdr;
+	struct rtattr *tb[SEG6_ATTR_MAX + 1] = {};
+	struct rtattr *attrs;
+
+	if (h->nlmsg_type != seg6_genl_family)
+		return 0;
+
+	len = h->nlmsg_len - NLMSG_LENGTH(GENL_HDRLEN);
+	if (len < 0) {
+		zlog_warn("%s: Message received from netlink is of a broken size %d %zu",
+			  __func__, h->nlmsg_len,
+			  (size_t)NLMSG_LENGTH(GENL_HDRLEN));
+		return -1;
+	}
+
+	ghdr = NLMSG_DATA(h);
+
+	if (ghdr->cmd != SEG6_CMD_GET_TUNSRC)
+		return 0;
+
+	attrs = (struct rtattr *)((char *)ghdr + GENL_HDRLEN);
+	netlink_parse_rtattr(tb, SEG6_ATTR_MAX, attrs, len);
+
+	if (tb[SEG6_ATTR_DST] == NULL) {
+		zlog_err("Missing tunsrc addr");
+		return -1;
+	}
+
+	zebra_srv6_encap_src_addr_set(
+		(struct in6_addr *)RTA_DATA(tb[SEG6_ATTR_DST]));
+
+	if (IS_ZEBRA_DEBUG_KERNEL)
+		zlog_debug("%s: SRv6 encap source address received from kernel: '%pI6'",
+			   __func__,
+			   (struct in6_addr *)RTA_DATA(tb[SEG6_ATTR_DST]));
+
+	return 0;
+}
+
+/**
+ * netlink_request_sr_tunsrc() - Request SR tunsrc from the kernel
+ * @zns:	Zebra namespace
+ *
+ * Return:	Result status
+ */
+static int netlink_request_sr_tunsrc(struct zebra_ns *zns)
+{
+	struct genl_request req;
+
+	if (zns->ge_netlink_cmd.sock < 0)
+		return -1;
+
+	if (seg6_genl_family < 0) {
+		zlog_err(
+			"Failed to get SRv6 encap source address: kernel does not support 'SEG6' Generic Netlink family.");
+		return -1;
+	}
+
+	/* Form the request, specifying filter (rtattr) if needed. */
+	memset(&req, 0, sizeof(req));
+	req.n.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type = seg6_genl_family;
+	req.g.cmd = SEG6_CMD_GET_TUNSRC;
+	req.g.version = SEG6_GENL_VERSION;
+
+	return netlink_request(&zns->ge_netlink_cmd, &req);
+}
+
+/**
+ * SR tunsrc read function using netlink interface. Only called
+ * on bootstrap time.
+ */
+int netlink_sr_tunsrc_read(struct zebra_ns *zns)
+{
+	int ret;
+	struct zebra_dplane_info dp_info;
+
+	if (zns->ge_netlink_cmd.sock < 0)
+		return -1;
+
+	/* Capture info in intermediate info struct */
+	dp_info.ns_id = zns->ns_id;
+	dp_info.is_cmd = true;
+	dp_info.sock = zns->ge_netlink_cmd.sock;
+	dp_info.seq = zns->ge_netlink_cmd.seq;
+
+	/* Get SR tunsrc. */
+	ret = netlink_request_sr_tunsrc(zns);
+	if (ret < 0)
+		return ret;
+	ret = netlink_parse_info(netlink_sr_tunsrc_reply_read,
+				 &zns->ge_netlink_cmd, &dp_info, 0, true);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+void ge_netlink_init(struct zebra_ns *zns)
+{
+	if (zns->ge_netlink_cmd.sock < 0)
+		return;
+
+	/*
+	 * Resolves the 'seg6' Generic Netlink family name to the corresponding numeric family identifier.
+	 * This will give us the numeric family identifier required to send 'seg6' commands to the kernel
+	 * over the Generic Netlink socket. 'seg6' commands are used to configure SRv6 internal parameters
+	 * such as the address to use as source for encapsulated packets.
+	 */
+	if (genl_resolve_family("SEG6"))
+		zlog_warn(
+			"Kernel does not support 'SEG6' Generic Netlink family. Any attempt to set the encapsulation parameters under the SRv6 configuration will fail");
+
+	/**
+	 * Retrieve the actual SRv6 encap source address from the kernel
+	 * (default namespace) and save it to zebra SRv6 config
+	 */
+	if (zns->ns_id == NS_DEFAULT)
+		netlink_sr_tunsrc_read(zns);
+}
+
+#endif /* HAVE_NETLINK */