From: Roy Marples <roy@marples.name>
Date: Wed, 23 Aug 2023 20:26:21 +0000 (+0100)
Subject: linux: Use the VRF link routing table in non manager
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fheads%2Fvrf;p=thirdparty%2Fdhcpcd.git

linux: Use the VRF link routing table in non manager

dhcpcd is limited it only one routing table and better VRF support
would need more extensive changes.
We detect the VRF table for the specificed interface when dhcpcd
initially creates routes and we use that table for lifetime of
the dhcpcd process.

Should address #238
---

diff --git a/src/if-linux.c b/src/if-linux.c
index cb389536..59840e58 100644
--- a/src/if-linux.c
+++ b/src/if-linux.c
@@ -273,6 +273,22 @@ check_proc_uint(struct dhcpcd_ctx *ctx, const char *path, unsigned int *u)
 	return 0;
 }
 
+static int
+parse_rtattr(struct rtattr *tb[], size_t max, struct rtattr *rta, size_t len)
+{
+	unsigned short type;
+
+	memset(tb, 0, sizeof(struct rtattr *) * (max + 1));
+	for (; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
+		type = (unsigned short)(rta->rta_type & NLA_TYPE_MASK);
+		if (type <= max && !tb[type])
+			tb[type] = rta;
+	}
+	return 0;
+}
+#define parse_rtattr_nested(tb, max, rta) \
+	(parse_rtattr((tb), (max), RTA_DATA(rta), RTA_PAYLOAD(rta)))
+
 static ssize_t
 if_writepathuint(struct dhcpcd_ctx *ctx, const char *path, unsigned int val)
 {
@@ -645,6 +661,7 @@ recv_again:
 static int
 if_copyrt(struct dhcpcd_ctx *ctx, struct rt *rt, struct nlmsghdr *nlm)
 {
+	struct priv *priv = ctx->priv;
 	size_t len;
 	struct rtmsg *rtm;
 	struct rtattr *rta;
@@ -657,7 +674,7 @@ if_copyrt(struct dhcpcd_ctx *ctx, struct rt *rt, struct nlmsghdr *nlm)
 		return -1;
 	}
 	rtm = (struct rtmsg *)NLMSG_DATA(nlm);
-	if (rtm->rtm_table != RT_TABLE_MAIN)
+	if (rtm->rtm_table != priv->rt_table)
 		return -1;
 
 	memset(rt, 0, sizeof(*rt));
@@ -1491,6 +1508,13 @@ struct nlma
 	char buffer[64];
 };
 
+struct nlmi
+{
+	struct nlmsghdr hdr;
+	struct ifinfomsg ifi;
+	char buffer[1024];
+};
+
 #ifdef INET
 struct ifiaddr
 {
@@ -1560,9 +1584,74 @@ struct nlmr
 	char buffer[256];
 };
 
+#ifdef IFLA_VRF_MAX
+static int
+_if_vrf_table(__unused struct dhcpcd_ctx *ctx,
+    void *arg, struct nlmsghdr *nlm)
+{
+	uint32_t *table = arg;
+	struct ifinfomsg *ifi;
+	size_t len;
+
+	struct rtattr *tb[IFLA_MAX + 1];
+	struct rtattr *li[IFLA_INFO_MAX + 1];
+	struct rtattr *vrf[IFLA_VRF_MAX + 1];
+
+	// Default to unspecified table
+	*table = 0;
+
+	ifi = NLMSG_DATA(nlm);
+	len = NLMSG_PAYLOAD(nlm, sizeof(*ifi));
+
+	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
+	if (!tb[IFLA_LINKINFO])
+		return 0;
+
+	parse_rtattr_nested(li, IFLA_INFO_MAX, tb[IFLA_LINKINFO]);
+
+	if (!li[IFLA_INFO_KIND] || strcmp(RTA_DATA(li[IFLA_INFO_KIND]), "vrf"))
+		return 0;
+
+	if (!li[IFLA_INFO_DATA])
+		return 0;
+
+	parse_rtattr_nested(vrf, IFLA_VRF_MAX, li[IFLA_INFO_DATA]);
+	if (vrf[IFLA_VRF_TABLE])
+		*table = *(uint32_t *)RTA_DATA(vrf[IFLA_VRF_TABLE]);
+
+	return 0;
+}
+
+static unsigned char
+if_vrf_table(const struct interface *ifp)
+{
+	uint32_t table;
+	struct nlmi nlm = {
+	    .hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
+	    .hdr.nlmsg_type = RTM_GETLINK,
+	    .hdr.nlmsg_flags = NLM_F_REQUEST,
+	    .ifi.ifi_family = AF_UNSPEC,
+	};
+
+	add_attr_l(&nlm.hdr, sizeof(nlm), IFLA_IFNAME,
+	    ifp->name, (unsigned short)(strlen(ifp->name) + 1));
+
+	int error = if_sendnetlink(ifp->ctx, NETLINK_ROUTE, &nlm.hdr,
+	    &_if_vrf_table, &table);
+	if (error == -1) {
+		logerr(__func__);
+		return 0;
+	}
+	return (unsigned char)table;
+}
+#else
+#define	if_vrf_table(ifp)	0
+#endif
+
 int
 if_route(unsigned char cmd, const struct rt *rt)
 {
+	struct priv *priv = rt->rt_ifp->ctx->priv;
 	struct nlmr nlm;
 	bool gateway_unspec;
 
@@ -1583,7 +1672,7 @@ if_route(unsigned char cmd, const struct rt *rt)
 	}
 	nlm.hdr.nlmsg_flags |= NLM_F_REQUEST;
 	nlm.rt.rtm_family = (unsigned char)rt->rt_dest.sa_family;
-	nlm.rt.rtm_table = RT_TABLE_MAIN;
+	nlm.rt.rtm_table = priv->rt_table;
 
 	gateway_unspec = sa_is_unspecified(&rt->rt_gateway);
 
@@ -1707,11 +1796,34 @@ _if_initrt(struct dhcpcd_ctx *ctx, void *arg,
 int
 if_initrt(struct dhcpcd_ctx *ctx, rb_tree_t *kroutes, int af)
 {
+	struct priv *priv = ctx->priv;
+
+#ifdef IFLA_VRF_MAX
+	if (!priv->rt_table) {
+		/* dhcpcd routing only works on one table.
+		 * For VRF we can work it out. */
+		struct interface *ifp;
+
+		if (!(ctx->options & DHCPCD_MANAGER)) {
+			if (!priv->rt_table) {
+				TAILQ_FOREACH(ifp, ctx->ifaces, next) {
+					if (ifp->active == IF_ACTIVE_USER)
+						break;
+				}
+				if (ifp)
+					priv->rt_table = if_vrf_table(ifp);
+			}
+		}
+	}
+#endif
+	if (!priv->rt_table)
+		priv->rt_table = RT_TABLE_MAIN;
+
 	struct nlmr nlm = {
 	    .hdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg)),
 	    .hdr.nlmsg_type = RTM_GETROUTE,
 	    .hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_MATCH,
-	    .rt.rtm_table = RT_TABLE_MAIN,
+	    .rt.rtm_table = priv->rt_table,
 	    .rt.rtm_family = (unsigned char)af,
 	};
 
diff --git a/src/if.h b/src/if.h
index df5f921e..2f614a23 100644
--- a/src/if.h
+++ b/src/if.h
@@ -137,6 +137,7 @@ struct priv {
 	int route_fd;
 	int generic_fd;
 	uint32_t route_pid;
+	unsigned char rt_table;
 };
 #endif
 #ifdef __sun