Temporary workaround, Joan Lledó is submitting a fixed version to
upstream.

---
 contrib/ports/unix/posixlib/include/posix/inet.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/contrib/ports/unix/posixlib/include/posix/inet.h
+++ b/contrib/ports/unix/posixlib/include/posix/inet.h
@@ -45,12 +45,14 @@ extern "C" {
 #define inet_addr_to_ip4addr(target_ipaddr, source_inaddr)   (ip4_addr_set_u32(target_ipaddr, (source_inaddr)->s_addr))
 
 #ifdef LWIP_UNIX_HURD
+#ifndef IP_PKTINFO
 #define IP_PKTINFO  8
 
 struct in_pktinfo {
   unsigned int   ipi_ifindex;  /* Interface index */
   struct in_addr ipi_addr;     /* Destination (from header) address */
 };
+#endif
 #endif /* LWIP_UNIX_HURD */
 
 #endif /* LWIP_IPV4 */
