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Add ipv6_get_data_any and ip_get_data_any.

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These version allow returning an extension header or other
non–upper-layer protocol if it is the final header before the end of the
packet. This is used to parse the broken packets sent as part of
protocol scan.
This commit is contained in:
david
2011-06-17 05:47:33 +00:00
parent 332c93ea07
commit e748e46d9e
2 changed files with 92 additions and 64 deletions
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153
libnetutil/netutil.cc
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@@ -541,8 +541,76 @@ unsigned short in_cksum(u16 *ptr,int nbytes) {
}
const void *ip_get_data(const void *packet, unsigned int *len,
struct abstract_ip_hdr *hdr) {
/* Return true iff this Next Header type is an extension header we must skip to
get to the upper-layer header. Types for which neither this function nor
ipv6_is_upperlayer return true are unknown and could be either. */
static int ipv6_is_extension_header(u8 type)
{
switch (type) {
case IP_PROTO_HOPOPTS:
case IP_PROTO_DSTOPTS:
case IP_PROTO_ROUTING:
case IP_PROTO_FRAGMENT:
/*
case IP_PROTO_ESP:
case IP_PROTO_AH:
*/
return 1;
default:
return 0;
}
}
/* Return true iff this Next Header type is a known upper-layer protocol, one
that isn't followed by any more headers. Types for which neither this
function nor ipv6_is_upperlayer return true are unknown and could be
either. */
static int ipv6_is_upperlayer(u8 type)
{
switch (type) {
case IP_PROTO_TCP:
case IP_PROTO_UDP:
case IP_PROTO_ICMP:
case IP_PROTO_ICMPV6:
case IP_PROTO_SCTP:
return 1;
default:
return 0;
}
}
/* upperlayer_only controls whether we require a known upper-layer protocol at
the end of the chain, or return the last readable header even if it is not an
upper-layer protocol (may even be another extension header). */
static const void *ipv6_get_data_primitive(const struct ip6_hdr *ip6,
unsigned int *len, u8 *nxt, bool upperlayer_only)
{
const unsigned char *p, *end;
if (*len < sizeof(*ip6))
return NULL;
p = (unsigned char *) ip6;
end = p + *len;
*nxt = ip6->ip6_nxt;
p += sizeof(*ip6);
while (p < end && ipv6_is_extension_header(*nxt)) {
if (p + 2 > end)
return NULL;
*nxt = *p;
p += (*(p + 1) + 1) * 8;
}
*len = end - p;
if (upperlayer_only && !ipv6_is_upperlayer(*nxt))
return NULL;
return (char *) p;
}
static const void *ip_get_data_primitive(const void *packet, unsigned int *len,
struct abstract_ip_hdr *hdr, bool upperlayer_only) {
const struct ip *ip;
ip = (struct ip *) packet;
@@ -583,12 +651,22 @@ const void *ip_get_data(const void *packet, unsigned int *len,
hdr->ttl = ip6->ip6_hlim;
hdr->ipid = ntohl(ip6->ip6_flow & IP6_FLOWLABEL_MASK);
return ipv6_get_data(ip6, len, &hdr->proto);
return ipv6_get_data_primitive(ip6, len, &hdr->proto, upperlayer_only);
}
return NULL;
}
const void *ip_get_data(const void *packet, unsigned int *len,
struct abstract_ip_hdr *hdr) {
return ip_get_data_primitive(packet, len, hdr, true);
}
const void *ip_get_data_any(const void *packet, unsigned int *len,
struct abstract_ip_hdr *hdr) {
return ip_get_data_primitive(packet, len, hdr, false);
}
/* Get the upper-layer protocol from an IPv4 packet. */
const void *ipv4_get_data(const struct ip *ip, unsigned int *len)
{
@@ -606,73 +684,20 @@ const void *ipv4_get_data(const struct ip *ip, unsigned int *len)
return (char *) ip + header_len;
}
/* Return true iff this Next Header type is an extension header we must skip to
get to the upper-layer header. Types for which neither this function nor
ipv6_is_upperlayer return true are unknown and could be either. */
static int ipv6_is_extension_header(u8 type)
{
switch (type) {
case IP_PROTO_HOPOPTS:
case IP_PROTO_DSTOPTS:
case IP_PROTO_ROUTING:
case IP_PROTO_FRAGMENT:
/*
case IP_PROTO_ESP:
case IP_PROTO_AH:
*/
return 1;
default:
return 0;
}
}
/* Return true iff this Next Header type is a known upper-layer protocol, one
that isn't followed by any more headers. Types for which neither this
function nor ipv6_is_upperlayer return true are unknown and could be
either. */
static int ipv6_is_upperlayer(u8 type)
{
switch (type) {
case IP_PROTO_TCP:
case IP_PROTO_UDP:
case IP_PROTO_ICMP:
case IP_PROTO_ICMPV6:
case IP_PROTO_SCTP:
return 1;
default:
return 0;
}
}
/* Get the upper-layer protocol from an IPv6 packet. This skips over known
extension headers. The length of the upper-layer payload is stored in *len.
The protocol is stored in *nxt. Returns NULL in case of error. */
const void *ipv6_get_data(const struct ip6_hdr *ip6, unsigned int *len, u8 *nxt)
{
const unsigned char *p, *end;
return ipv6_get_data_primitive(ip6, len, nxt, true);
}
if (*len < sizeof(*ip6))
return NULL;
p = (unsigned char *) ip6;
end = p + *len;
*nxt = ip6->ip6_nxt;
p += sizeof(*ip6);
while (ipv6_is_extension_header(*nxt)) {
if (p + 2 > end)
return NULL;
*nxt = *p;
p += (*(p + 1) + 1) * 8;
if (p > end)
return NULL;
}
*len = end - p;
if (!ipv6_is_upperlayer(*nxt))
return NULL;
return (char *) p;
/* Get the protocol payload from an IPv6 packet. This skips over known extension
headers. It differs from ipv6_get_data in that it will return a result even
if the final header is not a known upper-layer protocol. */
const void *ipv6_get_data_any(const struct ip6_hdr *ip6, unsigned int *len, u8 *nxt)
{
return ipv6_get_data_primitive(ip6, len, nxt, false);
}
const void *icmp_get_data(const struct icmp_hdr *icmp, unsigned int *len)