libiptc：添加带目标IP的DNAT规则

Question

我正在尝试使用libiptc创建一个c程序来创建端口转发规则。

static int insert_forward_rule(const char *table, const char *chain, unsigned int src, unsigned int dest, const char * ports, const char *target1, char * proto) {
struct xtc_handle *h;
struct ipt_entry *en = NULL;
struct ipt_entry * e;

struct ipt_entry_match * match_proto, * match_limit;
struct ipt_entry_target * target;
unsigned int size_ipt_entry, size_ipt_entry_match, size_ipt_entry_target, total_length;

size_ipt_entry = IPT_ALIGN(sizeof (struct ipt_entry));
size_ipt_entry_match = IPT_ALIGN(sizeof (struct ipt_entry_match)) + sizeof (struct ipt_tcp) + sizeof (int);
size_ipt_entry_target = IPT_ALIGN(sizeof (struct ipt_entry_target) + sizeof (IPTC_LABEL_ACCEPT));
total_length = 216; //size_ipt_entry + size_ipt_entry_match + size_ipt_entry_target + IPT_ALIGN(sizeof (struct ipt_natinfo)); //size_ipt_entry + 48 + 40
//printf("size of ipt ebtry=%u,match=%u,target=%u,total=%u
", size_ipt_entry, size_ipt_entry_match, size_ipt_entry_target, total_length);
//memory allocation for all structs that represent the netfilter rule we want to insert

e = calloc(1, total_length);
if (e == NULL) {
    printf("malloc failure");
    exit(1);
}
int size = 160;
//offsets to the other bits:
//target struct begining
e->target_offset = size; //size_ipt_entry + size_ipt_entry_match; //+ size_ipt_tcp + size_rateinfo + size_physdevinfo;
//next "e" struct, end of the current one
e->next_offset = total_length;
e->nfcache = NFC_IP_DST_PT;

if (dest) {
    e->ip.dst.s_addr = dest;
    e->ip.dmsk.s_addr = 0xFFFFFFFF;

}
match_limit = (struct ipt_entry_match *) (e->elems); //+ match_proto->u.match_size
match_limit->u.user.match_size = size_ipt_entry_match; //size_ipt_entry_match*3; //+ size_rateinfo;
strncpy(match_limit->u.user.name, "tcp", sizeof (match_limit->u.user.name)); //set name of the module, we will use in this match
struct ipt_tcp *info = (struct ipt_tcp *) match_limit->data;
unsigned int i = 0;
if (strchr(ports, ':') != NULL) {
    char aPort[2][10];
    sscanf(ports, "%[^:], %[^:]", aPort[0], aPort[1]);

    info->dpts[0] = atoi(aPort[0]);
    info->dpts[1] = atoi(aPort[1]);
} else {
    info->dpts[0] = info->dpts[1] = atoi(ports);

}
info->spts[0] = 0;
info->spts[1] = 0xFFFF;
e->ip.proto = IPPROTO_TCP;
printf("Target offset=%d,next offset=%d
", e->target_offset, e->next_offset);
target = (struct ipt_entry_target *) ((void*) e + e->target_offset); // + size_ipt_entry_match); //+ size_ipt_tcp + size_rateinfo + size_physdevinfo
size = 56;
target->u.user.target_size = size_ipt_entry_target + IPT_ALIGN(sizeof (struct nf_nat_range)); // size_ipt_entry_target;
target->u.user.revision = 0;
strncpy(target->u.user.name, target1, sizeof (target->u.user.name));
struct ipt_natinfo *inf = (struct ipt_natinfo*) target->data;
struct nf_nat_range range;
memset(&range, 0, sizeof (range));
range.flags |= IP_NAT_RANGE_MAP_IPS;
range.min_ip = range.max_ip = src;
inf->mr.rangesize++;
inf->mr.range[inf->mr.rangesize] = range;
inf->t.u.target_size = XT_ALIGN(sizeof (*inf) + inf->mr.rangesize * sizeof (struct nf_nat_range));


printf("after s_addr

");


//All the functions, mentioned below could be found in "Querying libiptc HOWTO" manual
h = iptc_init(table);
printf("h=%d
", h);
if (!h) {
    printf("Error initializing: %s
", iptc_strerror(errno));
    return 0;
}

printf("target_size=%d,match=%d,chain=%s,table=%s,target=%s
", target->u.user.target_size, match_limit->u.user.match_size, chain, table, target1);

int x = iptc_append_entry(chain, e, h);
if (!x) {
    printf("Error append_entry: %s
", iptc_strerror(errno));
    goto ERROR;
}
printf("%d,chain=%s,target=%s
", target->u.user.target_size, chain, table);
int y = iptc_commit(h);
if (!y) {
    printf("Error no=%d,commit: %s
", errno, iptc_strerror(errno));
    goto ERROR;
}
iptc_free(h);
if (e != NULL) {
    free(e);
    e = NULL;
}
return 1;
ERROR:
iptc_free(h);
if (e != NULL) {
    free(e);
    e = NULL;
}
return 0;
}

要调用此功能

inet_pton(AF_INET, "20.10.10.254", &a);
inet_pton(AF_INET, "20.10.10.100", &b);
insert_forward_rule("nat", "port_forward", b, a, "1111", "DNAT", "tcp");

每次我运行这段代码我都会得到错误作为无效的参数（代码22）。如果我将rangeize的位置更改为低于iptc_init（），那么它给出了错误代码94（非套接字上的套接字操作）我尝试了struct nf_nat_range结构直接然后它没有在规则中保存目标IP而不是它显示随机。我想做的规则是

iptables  -t nat -A port_forward -j DNAT -d 192.168.10.202 -p udp --dport 8080:8084 --to 20.10.10.112

用结构nf_nat_range创建的是

Chain port_forward (0 references)
pkts      bytes target     prot opt in     out     source               destination         
   0        0 DNAT       tcp  --  *      *       0.0.0.0/0            20.10.10.254        tcp dpt:1111 to: random 
   0        0 DNAT       tcp  --  *      *       0.0.0.0/0            20.10.10.254        tcp dpt:1111 to: random 
   0        0 DNAT       tcp  --  *      *       0.0.0.0/0            20.10.10.254        tcp dpt:1111 to: random