Repository : ssh://git@open-mesh.org/batctl
On branch : next
commit d348f8cb9d3dc45d92a8ab9bdd616cd82a5f589a Author: Sven Eckelmann sven@narfation.org Date: Mon Nov 5 21:25:27 2012 +0100
batctl: Use packing of 2 for all headers before an ethernet header
All packet headers in front of an ethernet header have to be completely divisible by 2 but not by 4 to make the payload after the ethernet header again 4 bytes boundary aligned.
A packing of 2 is necessary to avoid extra padding at the end of the struct caused by a structure member which is larger than two bytes. Otherwise the structure would not fulfill the previously mentioned rule to avoid the misalignment of the payload after the ethernet header. It may also lead to leakage of information when the padding it not initialized before sending.
Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Marek Lindner lindner_marek@yahoo.de
d348f8cb9d3dc45d92a8ab9bdd616cd82a5f589a packet.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/packet.h b/packet.h index 55e6935..cef1b3f 100644 --- a/packet.h +++ b/packet.h @@ -173,6 +173,18 @@ struct batadv_icmp_packet_rr { uint8_t rr[BATADV_RR_LEN][ETH_ALEN]; };
+/* All packet headers in front of an ethernet header have to be completely + * divisible by 2 but not by 4 to make the payload after the ethernet + * header again 4 bytes boundary aligned. + * + * A packing of 2 is necessary to avoid extra padding at the end of the struct + * caused by a structure member which is larger than two bytes. Otherwise + * the structure would not fulfill the previously mentioned rule to avoid the + * misalignment of the payload after the ethernet header. It may also lead to + * leakage of information when the padding it not initialized before sending. + */ +#pragma pack(2) + struct batadv_unicast_packet { struct batadv_header header; uint8_t ttvn; /* destination translation table version number */ @@ -212,7 +224,9 @@ struct batadv_bcast_packet { /* "4 bytes boundary + 2 bytes" long to make the payload after the * following ethernet header again 4 bytes boundary aligned */ -} __packed; +}; + +#pragma pack()
struct batadv_vis_packet { struct batadv_header header;