net/eth: Simplify _eth_get_rss_ex_dst_addr()

The length field is already contained in the ip6_ext_hdr structure.
Check it direcly in eth_parse_ipv6_hdr() before calling
_eth_get_rss_ex_dst_addr(), which gets a bit simplified.

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

net/eth.c

@@ -407,9 +407,7 @@ _eth_get_rss_ex_dst_addr(const struct iovec *pkt, int pkt_frags,
 {
     struct ip6_ext_hdr_routing *rthdr = (struct ip6_ext_hdr_routing *) ext_hdr;
 
-    if ((rthdr->rtype == 2) &&
-        (rthdr->len == sizeof(struct in6_address) / 8) &&
-        (rthdr->segleft == 1)) {
+    if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
 
         size_t input_size = iov_size(pkt, pkt_frags);
         size_t bytes_read;
@@ -528,10 +526,12 @@ bool eth_parse_ipv6_hdr(const struct iovec *pkt, int pkt_frags,
         }
 
         if (curr_ext_hdr_type == IP6_ROUTING) {
-            info->rss_ex_dst_valid =
-                _eth_get_rss_ex_dst_addr(pkt, pkt_frags,
-                                         ip6hdr_off + info->full_hdr_len,
-                                         &ext_hdr, &info->rss_ex_dst);
+            if (ext_hdr.ip6r_len == sizeof(struct in6_address) / 8) {
+                info->rss_ex_dst_valid =
+                    _eth_get_rss_ex_dst_addr(pkt, pkt_frags,
+                                             ip6hdr_off + info->full_hdr_len,
+                                             &ext_hdr, &info->rss_ex_dst);
+            }
         } else if (curr_ext_hdr_type == IP6_DESTINATON) {
             info->rss_ex_src_valid =
                 _eth_get_rss_ex_src_addr(pkt, pkt_frags,