[PATCH 2/3] rtnl_route: find lwtunnel encap type

[Mathis Marion]

From: Mathis Marion <mathis.marion at silabs.com>

This is necessary to decode RTA_ENCAP attributes. Therer are no
requirement regarding the placement of RTA_ENCAP_TYPE in relation to
RTA_ENCAP, so it must be found before decoding.
---
 src/rtnl_route.c | 37 +++++++++++++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/rtnl_route.c b/src/rtnl_route.c
index 331d35f53..6bb34cfd1 100644
--- a/src/rtnl_route.c
+++ b/src/rtnl_route.c
@@ -245,6 +245,34 @@ static const nla_decoder_t rtmsg_nla_decoders[] = {
 	[RTA_DPORT]		= decode_nla_u16
 };
 
+static uint16_t
+find_lwt_encap_type(struct tcb *const tcp,
+		    kernel_ulong_t addr,
+		    unsigned int len)
+{
+	uint16_t lwt_encap_type;
+	unsigned int nla_len;
+	struct nlattr nla;
+
+	while (len >= sizeof(struct nlattr)) {
+		if (!tfetch_obj(tcp, addr, &nla))
+			return 0;
+		if (nla.nla_len < NLA_HDRLEN)
+			return 0;
+
+		nla_len = MIN(nla.nla_len, len);
+		if ((nla.nla_type & NLA_TYPE_MASK) == RTA_ENCAP_TYPE &&
+		    nla_len - NLA_HDRLEN >= sizeof(lwt_encap_type) &&
+		    !umove(tcp, addr + NLA_HDRLEN, &lwt_encap_type))
+			return lwt_encap_type;
+
+		nla_len = NLA_ALIGN(nla.nla_len);
+                len  -= MIN(len, nla_len);
+		addr += nla_len;
+	}
+	return 0;
+}
+
 /*
  * RTA_MULTIPATH payload is a list of struct rtnexthop-headed RTA_* netlink
  * attributes:
@@ -258,6 +286,7 @@ decode_rta_multipath(struct tcb *const tcp,
 		     const unsigned int len,
 		     const void *const opaque_data)
 {
+	struct rtmsg_ctx ctx = *(const struct rtmsg_ctx *)opaque_data;
 	bool is_array = false;
 	struct rtnexthop nh;
 	kernel_ulong_t cur = addr;
@@ -294,12 +323,14 @@ decode_rta_multipath(struct tcb *const tcp,
 		tprint_struct_end();
 
 		if (rtnh_len > offset) {
+			ctx.lwt_encap_type = find_lwt_encap_type(tcp,
+								 addr + offset,
+								 len - offset);
 			tprint_array_next();
 			decode_nlattr(tcp, cur + offset, rtnh_len - offset,
 				      rtnl_route_attrs, "RTA_???",
 				      rtmsg_nla_decoders,
-				      ARRAY_SIZE(rtmsg_nla_decoders),
-				      opaque_data);
+				      ARRAY_SIZE(rtmsg_nla_decoders), &ctx);
 		}
 
 		if (rtnh_len > offset)
@@ -361,6 +392,8 @@ DECL_NETLINK_ROUTE_DECODER(decode_rtmsg)
 
 	offset = NLMSG_ALIGN(sizeof(ctx.rtmsg));
 	if (decode_nla && len > offset) {
+		ctx.lwt_encap_type = find_lwt_encap_type(tcp, addr + offset,
+							 len - offset);
 		tprint_array_next();
 		decode_nlattr(tcp, addr + offset, len - offset,
 			      rtnl_route_attrs, "RTA_???",
-- 
2.42.0