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Simplify EDNS0 packet size handling.

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In the post 2020 flag-day world, we limit UDP packets to 1232 bytes
which can go anywhere, so the dodgy code to try and determine the
functional maxmimum packet size on the path from upstream servers
is obsolete.
This commit is contained in:
Simon Kelley
2024-11-24 23:06:22 +00:00
parent 04d7693d86
commit f04cf8506a
5 changed files with 31 additions and 75 deletions
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27
src/edns0.c
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@@ -99,11 +99,9 @@ unsigned char *find_pseudoheader(struct dns_header *header, size_t plen, size_t
/* replace == 0 ->don't replace existing option
replace == 1 ->replace existing or add option
replace == 2 ->relpace existing option only.
udp_sz == 0 -> leave unchanged in existing EDNS0 or set to deamon->edns_pksz in a new one.
*/
size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *limit,
unsigned short udp_sz, int optno, unsigned char *opt, size_t optlen, int set_do, int replace)
int optno, unsigned char *opt, size_t optlen, int set_do, int replace)
{
unsigned char *lenp, *datap, *p, *udp_len, *buff = NULL;
int rdlen = 0, is_sign, is_last;
@@ -122,11 +120,7 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
p = udp_len;
if (udp_sz == 0)
GETSHORT(udp_sz, p);
else
PUTSHORT(udp_sz, p);
PUTSHORT(daemon->edns_pktsz, p);
GETSHORT(rcode, p);
GETSHORT(flags, p);
@@ -208,12 +202,9 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
return plen; /* bad packet */
}
if (udp_sz == 0)
udp_sz = daemon->edns_pktsz;
*p++ = 0; /* empty name */
PUTSHORT(T_OPT, p);
PUTSHORT(udp_sz, p); /* max packet length, 512 if not given in EDNS0 header */
PUTSHORT(daemon->edns_pktsz, p); /* max packet length, 512 if not given in EDNS0 header */
PUTSHORT(rcode, p); /* extended RCODE and version */
PUTSHORT(flags, p); /* DO flag */
lenp = p;
@@ -258,7 +249,7 @@ size_t add_pseudoheader(struct dns_header *header, size_t plen, unsigned char *l
size_t add_do_bit(struct dns_header *header, size_t plen, unsigned char *limit)
{
return add_pseudoheader(header, plen, (unsigned char *)limit, 0, 0, NULL, 0, 1, 0);
return add_pseudoheader(header, plen, (unsigned char *)limit, 0, NULL, 0, 1, 0);
}
static unsigned char char64(unsigned char c)
@@ -303,7 +294,7 @@ static size_t add_dns_client(struct dns_header *header, size_t plen, unsigned ch
replace = 2;
if (replace != 0 || maclen == 6)
plen = add_pseudoheader(header, plen, limit, 0, EDNS0_OPTION_NOMDEVICEID, (unsigned char *)encode, strlen(encode), 0, replace);
plen = add_pseudoheader(header, plen, limit, EDNS0_OPTION_NOMDEVICEID, (unsigned char *)encode, strlen(encode), 0, replace);
return plen;
}
@@ -328,7 +319,7 @@ static size_t add_mac(struct dns_header *header, size_t plen, unsigned char *lim
replace = 2;
if (replace != 0 || maclen != 0)
plen = add_pseudoheader(header, plen, limit, 0, EDNS0_OPTION_MAC, mac, maclen, 0, replace);
plen = add_pseudoheader(header, plen, limit, EDNS0_OPTION_MAC, mac, maclen, 0, replace);
return plen;
}
@@ -428,7 +419,7 @@ static size_t add_source_addr(struct dns_header *header, size_t plen, unsigned c
else
return plen;
return add_pseudoheader(header, plen, (unsigned char *)limit, 0, EDNS0_OPTION_CLIENT_SUBNET, (unsigned char *)&opt, len, 0, replace);
return add_pseudoheader(header, plen, (unsigned char *)limit, EDNS0_OPTION_CLIENT_SUBNET, (unsigned char *)&opt, len, 0, replace);
}
int check_source(struct dns_header *header, size_t plen, unsigned char *pseudoheader, union mysockaddr *peer)
@@ -528,7 +519,7 @@ static size_t add_umbrella_opt(struct dns_header *header, size_t plen, unsigned
PUTLONG(daemon->umbrella_asset, u);
}
return add_pseudoheader(header, plen, (unsigned char *)limit, 0, EDNS0_OPTION_UMBRELLA, (unsigned char *)&opt, u - (u8 *)&opt, 0, 1);
return add_pseudoheader(header, plen, (unsigned char *)limit, EDNS0_OPTION_UMBRELLA, (unsigned char *)&opt, u - (u8 *)&opt, 0, 1);
}
/* Set *check_subnet if we add a client subnet option, which needs to checked
@@ -543,7 +534,7 @@ size_t add_edns0_config(struct dns_header *header, size_t plen, unsigned char *l
plen = add_dns_client(header, plen, limit, source, now, cacheable);
if (daemon->dns_client_id)
plen = add_pseudoheader(header, plen, limit, 0, EDNS0_OPTION_NOMCPEID,
plen = add_pseudoheader(header, plen, limit, EDNS0_OPTION_NOMCPEID,
(unsigned char *)daemon->dns_client_id, strlen(daemon->dns_client_id), 0, 1);
if (option_bool(OPT_UMBRELLA))