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函数如下
void nf_nat_l4proto_unique_tuple(const struct nf_nat_l3proto *l3proto,
struct nf_conntrack_tuple *tuple,
const struct nf_nat_range *range,
enum nf_nat_manip_type maniptype,
const struct nf_conn *ct,
u16 *rover)
{
unsigned int range_size, min, i;
__be16 *portptr;
u_int16_t off;
if (maniptype == NF_NAT_MANIP_SRC)
portptr = &tuple->src.u.all;
else
portptr = &tuple->dst.u.all;
/* If no range specified... */
if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED)) {
/* If it's dst rewrite, can't change port */
if (maniptype == NF_NAT_MANIP_DST)
return;
if (ntohs(*portptr) < 1024) {
/* Loose convention: >> 512 is credential passing */
if (ntohs(*portptr) < 512) {
min = 1;
range_size = 511 - min + 1;
} else {
min = 600;
range_size = 1023 - min + 1;
}
} else {
min = 1024;
range_size = 65535 - 1024 + 1;
}
} else {
min = ntohs(range->min_proto.all);
range_size = ntohs(range->max_proto.all) - min + 1;
}
if (range->flags & NF_NAT_RANGE_PROTO_RANDOM)
off = l3proto->secure_port(tuple, maniptype == NF_NAT_MANIP_SRC
? tuple->dst.u.all
: tuple->src.u.all);
else
off = *rover;
for (i = 0; ; ++off) {
*portptr = htons(min + off % range_size);
if (++i != range_size && nf_nat_used_tuple(tuple, ct))
continue;
if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM))
*rover = off;
return;
}
return;
}
标红的部分，如果源端口在1024之下，为何转换的端口也需要在1024之下呢？这是出于什么考虑的。实在是没弄明白，多谢各位 |
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发表于 2016-12-30 17:52
。