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Merging my IGMP -sO patch. This adds build_igmp_raw() to easily build IGMP packets and uses it for -sO. Systems respond more when these packets are sent with an actual IGMP header. The RFC says they MUST verify the checksum, so that's most likely why I always got open|filtered instead of open. Since the different IGMP types all seem to have the checksum in the same place in the packet, it should at least tell us if it's supported or not even if the rest of the header is bogus (because the rest of the header has changed a little bit between the versions).

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kris
2007-01-17 17:40:16 +00:00
parent 2ce87a0250
commit 9ff574d50e
3 changed files with 85 additions and 0 deletions
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60
tcpip.cc
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@@ -1447,6 +1447,66 @@ return build_ip_raw(source, victim,
packetlen);
}
/* Builds an IGMP packet (including an IP header) by packing the fields
with the given information. It allocates a new buffer to store the
packet contents, and then returns that buffer. The packet is not
actually sent by this function. Caller must delete the buffer when
finished with the packet. The packet length is returned in packetlen,
which must be a valid int pointer.
*/
u8 *build_igmp_raw(const struct in_addr *source, const struct in_addr *victim,
int ttl, u16 ipid, u8 tos, bool df,
u8 *ipopt, int ipoptlen,
u8 ptype, u8 pcode,
char *data, u16 datalen, u32 *packetlen) {
struct {
u8 igmp_type;
u8 igmp_code;
u16 igmp_cksum;
u32 var; /* changes between types, unused. usually group address. */
u8 data[1500];
} igmp;
u32 *datastart = (u32 *) igmp.data;
int dlen = sizeof(igmp.data);
int igmplen = 0;
char *pkt = (char *) &igmp;
igmp.igmp_type = ptype;
igmp.igmp_code = pcode;
if (ptype == 0x11) { /* Membership Query */
igmplen = 8;
} else if (ptype == 0x12) { /* v1 Membership Report */
igmplen = 8;
} else if (ptype == 0x16) { /* v2 Membership Report */
igmplen = 8;
} else if (ptype == 0x17) { /* v2 Leave Group */
igmplen = 8;
} else if (ptype == 0x22) { /* v3 Membership Report */
igmplen = 8;
} else {
fatal("Unknown igmp type (%d) in build_igmp_raw", ptype);
}
if (datalen > 0) {
igmplen += MIN(dlen, datalen);
memset(datastart, 0, MIN(dlen, datalen));
}
igmp.igmp_cksum = 0;
igmp.igmp_cksum = in_cksum((unsigned short *)pkt, igmplen);
if (o.badsum)
--igmp.igmp_cksum;
return build_ip_raw(source, victim,
IPPROTO_IGMP,
ttl, get_random_u16(), tos, df,
ipopt, ipoptlen,
pkt, igmplen,
packetlen);
}
/* A simple function I wrote to help in debugging, shows the important fields
of a TCP packet*/