diff options
Diffstat (limited to 'libnet/include/libnet/libnet-structures.h')
| -rw-r--r-- | libnet/include/libnet/libnet-structures.h | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/libnet/include/libnet/libnet-structures.h b/libnet/include/libnet/libnet-structures.h index 38aff5d..eb7de76 100644 --- a/libnet/include/libnet/libnet-structures.h +++ b/libnet/include/libnet/libnet-structures.h @@ -79,8 +79,19 @@ struct libnet_protocol_block u_int8_t *buf; /* protocol buffer */ u_int32_t b_len; /* length of buf */ u_int16_t h_len; /* header length (for checksumming) */ - u_int32_t ip_offset; /* offset to IP header for csums */ - u_int32_t copied; /* bytes copied */ + /* Unused for IPV4_H block types. + * For protocols that sit on top of IP, it should be the the amount of + * buf that is the header, and will be included in the checksum. + */ + u_int32_t ip_offset; /* offset from end of pkt to beginning of IP header for csums */ + /* Unused for IPV4_H block types. + * For protocols that sit on top of IP (UDP, ICMP, ...), they often + * include some information from the IP header (in the form of a "pseudo + * header") in their own checksum calculation. To build that + * pseudo-header, thet need to find the real header. + */ + u_int32_t copied; /* bytes copied - the amount of data copied into buf */ + /* Used and updated by libnet_pblock_append(). */ u_int8_t type; /* type of pblock */ /* this needs to be updated every time a new packet builder is added */ #define LIBNET_PBLOCK_ARP_H 0x01 /* ARP header */ |