Infinband requires longer link-layer addresses and headers than Ethernet.

src/include/gpxe/netdevice.h

 struct device;
 
 /** Maximum length of a link-layer address */
-#define MAX_LL_ADDR_LEN 6
+#define MAX_LL_ADDR_LEN 20
 
 /** Maximum length of a link-layer header */
-#define MAX_LL_HEADER_LEN 16
+#define MAX_LL_HEADER_LEN 32
 
 /** Maximum length of a network-layer address */
 #define MAX_NET_ADDR_LEN 4