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udhcp6: fix problems found running against dnsmasq

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Patch is based on work by tiggerswelt.net. They say:
"
But when we tried to use dnsmasq on server-side, udhcpc6 was unable to
forward the acquired address to its setup-script although the
IPv6-Address had been assigned by the server as we could see via
tcpdump. We traced this issue down to a problem on how udhcpc6 parses
DHCPv6-Options: When moving to next option, a pointer-address is
increased and a length buffer is decreased by the length of the option.
The problem is that it is done in this order:

  option += 4 + option[3];
  len_m4 -= 4 + option[3];

But this has to be switched as the length is decreased by the length of
the *next* option, not the current one. This affected both - internal
checks if a required option is present and the function to expose
options to the environment of the setup-script.
There was also a bug parsing D6_OPT_STATUS_CODE Options, that made
dnsmasq not work as udhcpc6 thought it is receiving a non-positive
status-code (because it did not parse the status-code as required in RFC
3315).
In addition we introduced basic support for RFC 3646 (OPTION_DNS_SERVERS
and OPTION_DOMAIN_LIST) and RFC 4704 (OPTION_CLIENT_FQDN).
"

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-03-27 22:22:09 +02:00
parent e09f5e3045
commit 64d58aa806
2 changed files with 76 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
networking/udhcp/d6_common.h
View File

@ -81,9 +81,14 @@ struct d6_option {
#define D6_OPT_RECONF_MSG 19
#define D6_OPT_RECONF_ACCEPT 20
#define D6_OPT_DNS_SERVERS 23
#define D6_OPT_DOMAIN_LIST 24
#define D6_OPT_IA_PD 25
#define D6_OPT_IAPREFIX 26
#define D6_OPT_CLIENT_FQDN 39
/*** Other shared functions ***/
struct client6_data_t {

74
networking/udhcp/d6_dhcpc.c
View File

@ -86,6 +86,19 @@ enum {
IF_FEATURE_UDHCP_PORT( OPT_P = 1 << OPTBIT_P,)
};
static const char opt_req[] = {
(D6_OPT_ORO >> 8), (D6_OPT_ORO & 0xff),
0, 6,
(D6_OPT_DNS_SERVERS >> 8), (D6_OPT_DNS_SERVERS & 0xff),
(D6_OPT_DOMAIN_LIST >> 8), (D6_OPT_DOMAIN_LIST & 0xff),
(D6_OPT_CLIENT_FQDN >> 8), (D6_OPT_CLIENT_FQDN & 0xff)
};
static const char opt_fqdn_req[] = {
(D6_OPT_CLIENT_FQDN >> 8), (D6_OPT_CLIENT_FQDN & 0xff),
0, 2,
0, 0
};
/*** Utility functions ***/
@ -107,8 +120,8 @@ static void *d6_find_option(uint8_t *option, uint8_t *option_end, unsigned code)
/* Does its code match? */
if (option[1] == code)
return option; /* yes! */
option += option[3] + 4;
len_m4 -= option[3] + 4;
option += option[3] + 4;
}
return NULL;
}
@ -140,7 +153,9 @@ static char** new_env(void)
static void option_to_env(uint8_t *option, uint8_t *option_end)
{
/* "length minus 4" */
char *dlist, *ptr;
int len_m4 = option_end - option - 4;
int olen, ooff;
while (len_m4 >= 0) {
uint32_t v32;
char ipv6str[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff")];
@ -217,9 +232,54 @@ static void option_to_env(uint8_t *option, uint8_t *option_end)
sprint_nip6(ipv6str, option + 4 + 4 + 1);
*new_env() = xasprintf("ipv6prefix=%s/%u", ipv6str, (unsigned)(option[4 + 4]));
break;
case D6_OPT_DNS_SERVERS:
olen = ((option[2] << 8) | option[3]) / 16;
dlist = ptr = malloc (4 + olen * 40 - 1);
memcpy (ptr, "dns=", 4);
ptr += 4;
ooff = 0;
while (olen--) {
sprint_nip6(ptr, option + 4 + ooff);
ptr += 39;
ooff += 16;
if (olen)
*ptr++ = ' ';
}
*new_env() = dlist;
break;
case D6_OPT_DOMAIN_LIST:
dlist = dname_dec(option + 4, (option[2] << 8) | option[3], "search=");
if (!dlist)
break;
*new_env() = dlist;
break;
case D6_OPT_CLIENT_FQDN:
// Work around broken ISC DHCPD6
if (option[4] & 0xf8) {
olen = ((option[2] << 8) | option[3]);
dlist = xmalloc(olen);
//fixme:
//- explain
//- add len error check
//- merge two allocs into one
memcpy(dlist, option + 4, olen);
*new_env() = xasprintf("fqdn=%s", dlist);
free(dlist);
break;
}
dlist = dname_dec(option + 5, ((option[2] << 8) | option[3]) - 1, "fqdn=");
if (!dlist)
break;
*new_env() = dlist;
break;
}
option += 4 + option[3];
len_m4 -= 4 + option[3];
option += 4 + option[3];
}
}
@ -423,6 +483,10 @@ static NOINLINE int send_d6_discover(uint32_t xid, struct in6_addr *requested_ip
}
opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, len);
/* Request additional options */
opt_ptr = d6_store_blob(opt_ptr, &opt_req, sizeof(opt_req));
opt_ptr = d6_store_blob(opt_ptr, &opt_fqdn_req, sizeof(opt_fqdn_req));
/* Add options:
* "param req" option according to -O, options specified with -x
*/
@ -476,6 +540,10 @@ static NOINLINE int send_d6_select(uint32_t xid)
/* IA NA (contains requested IP) */
opt_ptr = d6_store_blob(opt_ptr, client6_data.ia_na, client6_data.ia_na->len + 2+2);
/* Request additional options */
opt_ptr = d6_store_blob(opt_ptr, &opt_req, sizeof(opt_req));
opt_ptr = d6_store_blob(opt_ptr, &opt_fqdn_req, sizeof(opt_fqdn_req));
/* Add options:
* "param req" option according to -O, options specified with -x
*/
@ -1306,7 +1374,7 @@ int udhcpc6_main(int argc UNUSED_PARAM, char **argv)
struct d6_option *option, *iaaddr;
type_is_ok:
option = d6_find_option(packet.d6_options, packet_end, D6_OPT_STATUS_CODE);
if (option && option->data[4] != 0) {
if (option && (option->data[0] | option->data[1]) != 0) {
/* return to init state */
bb_error_msg("received DHCP NAK (%u)", option->data[4]);
d6_run_script(&packet, "nak");