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Exclude EDE before other EDNS options when there isn't enough space

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This commit is contained in:
Natalie Reece 2023-07-11 17:01:26 -06:00
parent 7240ecbeb0
commit 67e52ea9c5
2 changed files with 48 additions and 9 deletions
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49
util/data/msgencode.c
View file

@ -806,6 +806,24 @@ calc_edns_field_size(struct edns_data* edns)
return 1 + 2 + 2 + 4 + 2 + rdatalen;
}
uint16_t
calc_edns_option_size(struct edns_data* edns, uint16_t code)
{
size_t rdatalen = 0;
struct edns_option* opt;
if(!edns || !edns->edns_present)
return 0;
for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
if (opt->opt_code == code)
rdatalen += 4 + opt->opt_len;
}
for(opt = edns->opt_list_out; opt; opt = opt->next) {
if (opt->opt_code == code)
rdatalen += 4 + opt->opt_len;
}
return rdatalen;
}
static void
attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
uint16_t max_msg_sz)
@ -918,23 +936,30 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
return 0;
if(sldns_buffer_capacity(pkt) < udpsize)
udpsize = sldns_buffer_capacity(pkt);
if(udpsize < LDNS_HEADER_SIZE + calc_edns_field_size(edns)) {
if(udpsize < LDNS_HEADER_SIZE + calc_edns_field_size(edns) -
calc_edns_option_size(edns, LDNS_EDNS_EDE)) {
/* packet too small to contain edns, omit it. */
attach_edns = 0;
} else {
/* reserve space for edns record */
attach_edns = (unsigned int)calc_edns_field_size(edns);
udpsize -= attach_edns;
attach_edns = (unsigned int)calc_edns_field_size(edns) -
calc_edns_option_size(edns, LDNS_EDNS_EDE);
}
if(!reply_info_encode(qinf, rep, id, flags, pkt, timenow, region,
udpsize, dnssec, MINIMAL_RESPONSES)) {
udpsize - attach_edns, dnssec, MINIMAL_RESPONSES)) {
log_err("reply encode: out of memory");
return 0;
}
if(attach_edns && sldns_buffer_capacity(pkt) >=
sldns_buffer_limit(pkt)+attach_edns)
attach_edns_record_max_msg_sz(pkt, edns, udpsize+attach_edns);
if(attach_edns) {
if(udpsize >= sldns_buffer_limit(pkt)+calc_edns_field_size(edns))
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
else if(udpsize >= sldns_buffer_limit(pkt) + attach_edns) {
edns_opt_list_remove(&edns->opt_list_inplace_cb_out, LDNS_EDNS_EDE);
edns_opt_list_remove(&edns->opt_list_out, LDNS_EDNS_EDE);
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
}
}
return 1;
}
@ -996,8 +1021,14 @@ error_encode(sldns_buffer* buf, int r, struct query_info* qinfo,
es.ext_rcode = 0;
es.bits &= EDNS_DO;
if(sldns_buffer_limit(buf) + calc_edns_field_size(&es) >
edns->udp_size)
return;
edns->udp_size) {
edns_opt_list_remove(&es.opt_list_inplace_cb_out, LDNS_EDNS_EDE);
edns_opt_list_remove(&es.opt_list_out, LDNS_EDNS_EDE);
if(sldns_buffer_limit(buf) + calc_edns_field_size(&es) >
edns->udp_size) {
return;
}
}
attach_edns_record(buf, &es);
}
}

8
util/data/msgencode.h
View file

@ -108,6 +108,14 @@ void qinfo_query_encode(struct sldns_buffer* pkt, struct query_info* qinfo);
*/
uint16_t calc_edns_field_size(struct edns_data* edns);
/**
* Calculate the size of a specific EDNS option in packet.
* @param edns: edns data or NULL.
* @param code: the opt code to get the size of.
* @return octets the option will take up.
*/
uint16_t calc_edns_option_size(struct edns_data* edns, uint16_t code);
/**
* Attach EDNS record to buffer. Buffer has complete packet. There must
* be enough room left for the EDNS record.