1 files changed, 59 insertions, 0 deletions
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index e30515f89802..cf36f955bfe6 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -1116,6 +1116,65 @@ error:
 	goto drop;
 }
 
+static bool ip_icmp_error_rfc4884_validate(const struct sk_buff *skb, int off)
+{
+	struct icmp_extobj_hdr *objh, _objh;
+	struct icmp_ext_hdr *exth, _exth;
+	u16 olen;
+
+	exth = skb_header_pointer(skb, off, sizeof(_exth), &_exth);
+	if (!exth)
+		return false;
+	if (exth->version != 2)
+		return true;
+
+	if (exth->checksum &&
+	    csum_fold(skb_checksum(skb, off, skb->len - off, 0)))
+		return false;
+
+	off += sizeof(_exth);
+	while (off < skb->len) {
+		objh = skb_header_pointer(skb, off, sizeof(_objh), &_objh);
+		if (!objh)
+			return false;
+
+		olen = ntohs(objh->length);
+		if (olen < sizeof(_objh))
+			return false;
+
+		off += olen;
+		if (off > skb->len)
+			return false;
+	}
+
+	return true;
+}
+
+void ip_icmp_error_rfc4884(const struct sk_buff *skb,
+			   struct sock_ee_data_rfc4884 *out,
+			   int thlen, int off)
+{
+	int hlen;
+
+	/* original datagram headers: end of icmph to payload (skb->data) */
+	hlen = -skb_transport_offset(skb) - thlen;
+
+	/* per rfc 4884: minimal datagram length of 128 bytes */
+	if (off < 128 || off < hlen)
+		return;
+
+	/* kernel has stripped headers: return payload offset in bytes */
+	off -= hlen;
+	if (off + sizeof(struct icmp_ext_hdr) > skb->len)
+		return;
+
+	out->len = off;
+
+	if (!ip_icmp_error_rfc4884_validate(skb, off))
+		out->flags |= SO_EE_RFC4884_FLAG_INVALID;
+}
+EXPORT_SYMBOL_GPL(ip_icmp_error_rfc4884);
+
 int icmp_err(struct sk_buff *skb, u32 info)
 {
 	struct iphdr *iph = (struct iphdr *)skb->data;