net/eth: Check size earlier in _eth_get_rss_ex_dst_addr()

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Miroslav Rezanina <mrezanin@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

net/eth.c

@@ -406,16 +406,14 @@ _eth_get_rss_ex_dst_addr(const struct iovec *pkt, int pkt_frags,
                         struct in6_address *dst_addr)
 {
     struct ip6_ext_hdr_routing *rthdr = (struct ip6_ext_hdr_routing *) ext_hdr;
+    size_t input_size = iov_size(pkt, pkt_frags);
+    size_t bytes_read;
 
-    if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
-
-        size_t input_size = iov_size(pkt, pkt_frags);
-        size_t bytes_read;
-
-        if (input_size < ext_hdr_offset + sizeof(*ext_hdr)) {
-            return false;
-        }
+    if (input_size < ext_hdr_offset + sizeof(*ext_hdr)) {
+        return false;
+    }
 
+    if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
         bytes_read = iov_to_buf(pkt, pkt_frags,
                                 ext_hdr_offset + sizeof(*rthdr),
                                 dst_addr, sizeof(*dst_addr));