system-linux: make encaplimit configurable for ip6 tunnels (FS#1501)

Make encapsulation limit of IP6 tunnels configurable for the ds-lite/map
proto shell handlers as not all ISPs support the destination option header
containing the tunnel encapsulation limit value as reported in FS#1501.

The IP6 tunnel specific setting encaplimit is parsed as a nested json
data object; setting it to ignore disables the insertion of the
destination option header while a value from 0 till 255 sets the
tunnel encapsulation limit accordingly in the destination option header.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

3 files changed, 50 insertions, 18 deletions

diff --git a/system-linux.c b/system-linux.c
index 2a108e2..0127b01 100644
--- a/system-linux.c
+++ b/system-linux.c
@@ -2300,7 +2300,6 @@ static int system_add_ip6_tunnel(const char *name, const unsigned int link,
 
 	nla_put_u8(nlm, IFLA_IPTUN_PROTO, IPPROTO_IPIP);
 	nla_put_u8(nlm, IFLA_IPTUN_TTL, (ttl) ? ttl : 64);
-	nla_put_u8(nlm, IFLA_IPTUN_ENCAP_LIMIT, 4);
 
 	struct in6_addr in6buf;
 	if ((cur = tb[TUNNEL_ATTR_LOCAL])) {
@@ -2319,26 +2318,41 @@ static int system_add_ip6_tunnel(const char *name, const unsigned int link,
 		nla_put(nlm, IFLA_IPTUN_REMOTE, sizeof(in6buf), &in6buf);
 	}
 
-#ifdef IFLA_IPTUN_FMR_MAX
 	if ((cur = tb[TUNNEL_ATTR_DATA])) {
-		struct blob_attr *dcur;
-		unsigned drem, fmrcnt = 0;
-		struct nlattr *fmrs = nla_nest_start(nlm, IFLA_IPTUN_FMRS);
+		struct blob_attr *tb_data[__IPIP6_DATA_ATTR_MAX];
 
-		if (!fmrs) {
-			ret = -ENOMEM;
-			goto failure;
-		}
+		blobmsg_parse(ipip6_data_attr_list.params, __IPIP6_DATA_ATTR_MAX, tb_data,
+			blobmsg_data(cur), blobmsg_len(cur));
 
-		blobmsg_for_each_attr(dcur, cur, drem) {
-			if (blobmsg_type(dcur) != BLOBMSG_TYPE_ARRAY ||
-					strcmp(blobmsg_name(dcur), "fmrs") ||
-					blobmsg_check_array(dcur, BLOBMSG_TYPE_UNSPEC) <= 0)
-				continue;
+		if ((cur = tb_data[IPIP6_DATA_ENCAPLIMIT])) {
+			char *str = blobmsg_get_string(cur);
+
+			if (strcmp(str, "ignore")) {
+				char *e;
+				unsigned encap_limit = strtoul(str, &e, 0);
+
+				if (e == str || *e || encap_limit > 255) {
+					ret = -EINVAL;
+					goto failure;
+				}
 
+				nla_put_u8(nlm, IFLA_IPTUN_ENCAP_LIMIT, encap_limit);
+			} else
+				nla_put_u32(nlm, IFLA_IPTUN_FLAGS, IP6_TNL_F_IGN_ENCAP_LIMIT);
+		}
+
+#ifdef IFLA_IPTUN_FMR_MAX
+		if ((cur = tb_data[IPIP6_DATA_FMRS])) {
 			struct blob_attr *rcur;
-			unsigned rrem;
-			blobmsg_for_each_attr(rcur, dcur, rrem) {
+			unsigned rrem, fmrcnt = 0;
+			struct nlattr *fmrs = nla_nest_start(nlm, IFLA_IPTUN_FMRS);
+
+			if (!fmrs) {
+				ret = -ENOMEM;
+				goto failure;
+			}
+
+			blobmsg_for_each_attr(rcur, cur, rrem) {
 				struct blob_attr *tb_fmr[__FMR_DATA_ATTR_MAX], *tb_cur;
 				struct in6_addr ip6prefix;
 				struct in_addr ip4prefix;
@@ -2390,10 +2404,11 @@ static int system_add_ip6_tunnel(const char *name, const unsigned int link,
 
 				nla_nest_end(nlm, rule);
 			}
+
+			nla_nest_end(nlm, fmrs);
 		}
-		nla_nest_end(nlm, fmrs);
-	}
 #endif
+	}
 
 	nla_nest_end(nlm, infodata);
 	nla_nest_end(nlm, linkinfo);
diff --git a/system.c b/system.c
index e236e96..f96708d 100644
--- a/system.c
+++ b/system.c
@@ -79,6 +79,16 @@ const struct uci_blob_param_list sixrd_data_attr_list = {
 	.params = sixrd_data_attrs,
 };
 
+static const struct blobmsg_policy ipip6_data_attrs[__SIXRD_DATA_ATTR_MAX] = {
+	[IPIP6_DATA_ENCAPLIMIT] = { .name = "encaplimit", .type = BLOBMSG_TYPE_STRING },
+	[IPIP6_DATA_FMRS] = { .name = "fmrs", .type = BLOBMSG_TYPE_ARRAY },
+};
+
+const struct uci_blob_param_list ipip6_data_attr_list = {
+	.n_params = __IPIP6_DATA_ATTR_MAX,
+	.params = ipip6_data_attrs,
+};
+
 static const struct blobmsg_policy fmr_data_attrs[__FMR_DATA_ATTR_MAX] = {
 	[FMR_DATA_PREFIX6] = { .name = "prefix6", .type = BLOBMSG_TYPE_STRING },
 	[FMR_DATA_PREFIX4] = { .name = "prefix4", .type = BLOBMSG_TYPE_STRING },
diff --git a/system.h b/system.h
index 371a524..683dc18 100644
--- a/system.h
+++ b/system.h
@@ -68,6 +68,12 @@ enum sixrd_data {
 	__SIXRD_DATA_ATTR_MAX
 };
 
+enum ipip6_data {
+	IPIP6_DATA_ENCAPLIMIT,
+	IPIP6_DATA_FMRS,
+	__IPIP6_DATA_ATTR_MAX
+};
+
 enum fmr_data {
 	FMR_DATA_PREFIX6,
 	FMR_DATA_PREFIX4,
@@ -80,6 +86,7 @@ extern const struct uci_blob_param_list vxlan_data_attr_list;
 extern const struct uci_blob_param_list gre_data_attr_list;
 extern const struct uci_blob_param_list vti_data_attr_list;
 extern const struct uci_blob_param_list sixrd_data_attr_list;
+extern const struct uci_blob_param_list ipip6_data_attr_list;
 extern const struct uci_blob_param_list fmr_data_attr_list;
 
 enum bridge_opt {