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- For #911: Try to trim EXTRA-TEXT (and LDNS_EDE_OTHER options

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altogether) before giving up on attaching EDE options.
This commit is contained in:
George Thessalonikefs
2023-08-01 09:55:28 +02:00
parent dcd0191d7e
commit 08e11284fb
3 changed files with 312 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
util/data/msgencode.c
+85 -8
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@@ -814,16 +814,85 @@ calc_edns_option_size(struct edns_data* edns, uint16_t code)
if(!edns || !edns->edns_present)
return 0;
for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
if (opt->opt_code == code)
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)
if(opt->opt_code == code)
rdatalen += 4 + opt->opt_len;
}
return rdatalen;
}
uint16_t
calc_ede_option_size(struct edns_data* edns, uint16_t* txt_size)
{
size_t rdatalen = 0;
struct edns_option* opt;
*txt_size = 0;
if(!edns || !edns->edns_present)
return 0;
for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
if(opt->opt_code == LDNS_EDNS_EDE)
rdatalen += 4 + opt->opt_len;
if(opt->opt_len > 2)
*txt_size += opt->opt_len - 2;
if(opt->opt_len >= 2 && sldns_read_uint16(
opt->opt_data) == LDNS_EDE_OTHER)
*txt_size += 4 + 2;
}
for(opt = edns->opt_list_out; opt; opt = opt->next) {
if(opt->opt_code == LDNS_EDNS_EDE)
rdatalen += 4 + opt->opt_len;
if(opt->opt_len > 2)
*txt_size += opt->opt_len - 2;
if(opt->opt_len >= 2 && sldns_read_uint16(
opt->opt_data) == LDNS_EDE_OTHER)
*txt_size += 4 + 2;
}
return rdatalen;
}
/* Trims the EDE OPTION-DATA to not include any EXTRA-TEXT data.
* Also removes any LDNS_EDE_OTHER options from the list since they are useless
* without the extra text. */
static void
ede_trim_text(struct edns_option** list)
{
struct edns_option* curr, *prev = NULL;
if(!list || !(*list)) return;
/* Unlink and repoint if LDNS_EDE_OTHER are first in list */
while(list && *list && (*list)->opt_code == LDNS_EDNS_EDE
&& (*list)->opt_len >= 2
&& sldns_read_uint16((*list)->opt_data) == LDNS_EDE_OTHER ) {
*list = (*list)->next;
}
if(!list || !(*list)) return;
curr = *list;
while(curr) {
if(curr->opt_code == LDNS_EDNS_EDE) {
if(curr->opt_len >= 2 && sldns_read_uint16(
curr->opt_data) == LDNS_EDE_OTHER) {
/* LDNS_EDE_OTHER cannot be the first option in
* this while, so prev is always initialized at
* this point from the other branches;
* cut this option off */
prev->next = curr->next;
curr = curr->next;
} else if(curr->opt_len > 2) {
/* trim this option's EXTRA-TEXT */
curr->opt_len = 2;
prev = curr;
curr = curr->next;
}
} else {
/* continue */
prev = curr;
curr = curr->next;
}
}
}
static void
attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
uint16_t max_msg_sz)
@@ -912,6 +981,7 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
{
uint16_t flags;
unsigned int attach_edns = 0;
uint16_t edns_field_size, ede_size, ede_txt_size;
if(!cached || rep->authoritative) {
/* original flags, copy RD and CD bits from query. */
@@ -934,16 +1004,19 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
log_assert(flags & BIT_QR); /* QR bit must be on in our replies */
if(udpsize < LDNS_HEADER_SIZE)
return 0;
/* currently edns does not change during calculations;
* calculate sizes once here */
edns_field_size = calc_edns_field_size(edns);
ede_size = calc_ede_option_size(edns, &ede_txt_size);
if(sldns_buffer_capacity(pkt) < udpsize)
udpsize = sldns_buffer_capacity(pkt);
if(udpsize < LDNS_HEADER_SIZE + calc_edns_field_size(edns) -
calc_edns_option_size(edns, LDNS_EDNS_EDE)) {
/* EDEs are optional, try to fit anything else before them */
if(udpsize < LDNS_HEADER_SIZE + edns_field_size - ede_size) {
/* 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) -
calc_edns_option_size(edns, LDNS_EDNS_EDE);
attach_edns = (unsigned int)edns_field_size - ede_size;
}
if(!reply_info_encode(qinf, rep, id, flags, pkt, timenow, region,
@@ -952,9 +1025,13 @@ reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
return 0;
}
if(attach_edns) {
if(udpsize >= sldns_buffer_limit(pkt)+calc_edns_field_size(edns))
if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size)
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
else if(udpsize >= sldns_buffer_limit(pkt) + attach_edns) {
else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_txt_size) {
ede_trim_text(&edns->opt_list_inplace_cb_out);
ede_trim_text(&edns->opt_list_out);
attach_edns_record_max_msg_sz(pkt, edns, udpsize);
} else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_size) {
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);