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dns.c: change dns_send/dns_recv to operate on pbuf, not on contiguous buffer -> dns_payload_buffer/DNS_MSG_SIZE can be removed

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This commit is contained in:
Simon Goldschmidt 2014-09-16 19:33:20 +02:00
parent e303f30d10
commit 56c6301089
3 changed files with 65 additions and 82 deletions
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3
CHANGELOG
View File

@ -6,6 +6,9 @@ HISTORY
++ New features:
2014-09-16: Simon Goldschmidt
* dns.c, opt.h: reduced ram usage by parsing DNS responses in place
2014-09-16: Simon Goldschmidt
* pbuf.h/.c: added pbuf_take_at() and pbuf_put_at()

139
src/core/dns.c
View File

@ -293,9 +293,6 @@ static u8_t dns_seqno;
static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
static struct dns_req_entry dns_requests[DNS_MAX_REQUESTS];
static ip_addr_t dns_servers[DNS_MAX_SERVERS];
/** Contiguous buffer for processing responses */
static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)];
static u8_t* dns_payload;
#ifndef LWIP_DNS_STRICMP
#define LWIP_DNS_STRICMP(str1, str2) dns_stricmp(str1, str2)
@ -345,8 +342,6 @@ dns_init()
LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer);
/* initialize default DNS server address */
DNS_SERVER_ADDRESS(&dnsserver);
@ -598,50 +593,53 @@ dns_lookup(const char *name)
* any more).
*
* @param query hostname (not encoded) from the dns_table
* @param response encoded hostname in the DNS response
* @return 0: names equal; 1: names differ
* @param p pbuf containing the encoded hostname in the DNS response
* @param start_offset offset into p where the name starts
* @return 0xFFFF: names differ, other: names equal -> offset behind name
*/
static char*
dns_compare_name(char *query, char *response)
static u16_t
dns_compare_name(char *query, struct pbuf* p, u16_t start_offset)
{
unsigned char n;
u16_t response_offset = start_offset;
do {
n = *response++;
n = pbuf_get_at(p, response_offset++);
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name: cannot be equal since we don't send them */
return NULL;
return 0xFFFF;
} else {
/* Not compressed name */
while (n > 0) {
if ((*query) != (*response)) {
return NULL;
if ((*query) != pbuf_get_at(p, response_offset)) {
return 0xFFFF;
}
++response;
++response_offset;
++query;
--n;
};
++query;
}
} while (*response != 0);
} while (pbuf_get_at(p, response_offset) != 0);
return response + 1;
return response_offset + 1;
}
/**
* Walk through a compact encoded DNS name and return the end of the name.
*
* @param query encoded DNS name in the DNS server response
* @return end of the name
* @param p pbuf containing the name
* @param query_idx start index into p pointing to encoded DNS name in the DNS server response
* @return index to end of the name
*/
static char *
dns_parse_name(char *query)
static u16_t
dns_parse_name(struct pbuf* p, u16_t query_idx)
{
unsigned char n;
do {
n = (unsigned char) *query++;
n = pbuf_get_at(p, query_idx++);
/** @see RFC 1035 - 4.1.4. Message compression */
if ((n & 0xc0) == 0xc0) {
/* Compressed name */
@ -649,13 +647,13 @@ dns_parse_name(char *query)
} else {
/* Not compressed name */
while (n > 0) {
++query;
++query_idx;
--n;
};
}
} while (*query != 0);
} while (pbuf_get_at(p, query_idx) != 0);
return query + 1;
return query_idx + 1;
}
/**
@ -668,11 +666,11 @@ static err_t
dns_send(struct dns_table_entry* entry)
{
err_t err;
struct dns_hdr *hdr;
struct dns_hdr hdr;
struct dns_query qry;
struct pbuf *p;
char *query, *nptr;
const char *pHostname;
u16_t query_idx, copy_len;
const char *hostname, *hostname_part;
u8_t n;
u8_t pcb_idx;
@ -682,44 +680,38 @@ dns_send(struct dns_table_entry* entry)
LWIP_ASSERT("dns server has no IP address set", !ip_addr_isany(&dns_servers[entry->server_idx]));
/* if here, we have either a new query or a retry on a previous query to process */
p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH + 1 +
p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
SIZEOF_DNS_QUERY, PBUF_RAM);
if (p != NULL) {
u16_t realloc_size;
LWIP_ASSERT("pbuf must be in one piece", p->next == NULL);
/* fill dns header */
hdr = (struct dns_hdr*)p->payload;
memset(hdr, 0, SIZEOF_DNS_HDR);
hdr->id = htons(entry->txid);
hdr->flags1 = DNS_FLAG1_RD;
hdr->numquestions = PP_HTONS(1);
query = (char*)hdr + SIZEOF_DNS_HDR;
pHostname = entry->name;
--pHostname;
memset(&hdr, 0, SIZEOF_DNS_HDR);
hdr.id = htons(entry->txid);
hdr.flags1 = DNS_FLAG1_RD;
hdr.numquestions = PP_HTONS(1);
pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
hostname = entry->name;
--hostname;
/* convert hostname into suitable query format. */
query_idx = SIZEOF_DNS_HDR;
do {
++pHostname;
nptr = query;
++query;
for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) {
*query = *pHostname;
++query;
++hostname;
hostname_part = hostname;
for(n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
++n;
}
*nptr = n;
} while(*pHostname != 0);
*query++='\0';
copy_len = hostname - hostname_part;
pbuf_put_at(p, query_idx, n);
pbuf_take_at(p, hostname_part, copy_len, query_idx + 1);
query_idx += n + 1;
} while(*hostname != 0);
pbuf_put_at(p, query_idx, 0);
query_idx++;
/* fill dns query */
qry.type = PP_HTONS(DNS_RRTYPE_A);
qry.cls = PP_HTONS(DNS_RRCLASS_IN);
SMEMCPY(query, &qry, SIZEOF_DNS_QUERY);
/* resize pbuf to the exact dns query */
realloc_size = (u16_t)((query + SIZEOF_DNS_QUERY) - ((char*)(p->payload)));
LWIP_ASSERT("p->tot_len >= realloc_size", p->tot_len >= realloc_size);
pbuf_realloc(p, realloc_size);
pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
#if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
pcb_idx = entry->pcb_idx;
@ -991,8 +983,8 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
{
u8_t i, entry_idx = DNS_TABLE_SIZE;
u16_t txid;
char *ptr;
struct dns_hdr *hdr;
u16_t res_idx;
struct dns_hdr hdr;
struct dns_answer ans;
struct dns_query qry;
u16_t nquestions, nanswers;
@ -1001,13 +993,6 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
LWIP_UNUSED_ARG(pcb);
LWIP_UNUSED_ARG(port);
/* is the dns message too big ? */
if (p->tot_len > DNS_MSG_SIZE) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n"));
/* free pbuf and return */
goto memerr;
}
/* is the dns message big enough ? */
if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
@ -1016,10 +1001,9 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
}
/* copy dns payload inside static buffer for processing */
if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) {
if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
/* Match the ID in the DNS header with the name table. */
hdr = (struct dns_hdr*)dns_payload;
txid = htons(hdr->id);
txid = htons(hdr.id);
for (i = 0; i < DNS_TABLE_SIZE; i++) {
struct dns_table_entry *entry = &dns_table[i];
entry_idx = i;
@ -1028,15 +1012,15 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
u8_t dns_err;
/* This entry is now completed. */
entry->state = DNS_STATE_DONE;
dns_err = hdr->flags2 & DNS_FLAG2_ERR_MASK;
dns_err = hdr.flags2 & DNS_FLAG2_ERR_MASK;
/* We only care about the question(s) and the answers. The authrr
and the extrarr are simply discarded. */
nquestions = htons(hdr->numquestions);
nanswers = htons(hdr->numanswers);
nquestions = htons(hdr.numquestions);
nanswers = htons(hdr.numanswers);
/* Check for error. If so, call callback to inform. */
if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (dns_err != 0) || (nquestions != 1)) {
if (((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) || (dns_err != 0) || (nquestions != 1)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
@ -1051,38 +1035,39 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
/* Check if the name in the "question" part match with the name in the entry and
skip it if equal. */
ptr = dns_compare_name(entry->name, (char*)dns_payload + SIZEOF_DNS_HDR);
if (ptr == NULL) {
res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
if (res_idx == 0xFFFF) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* check if "question" part matches the request */
SMEMCPY(&qry, ptr, SIZEOF_DNS_QUERY);
pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx);
if((qry.type != PP_HTONS(DNS_RRTYPE_A)) || (qry.cls != PP_HTONS(DNS_RRCLASS_IN))) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
/* call callback to indicate error, clean up memory and return */
goto responseerr;
}
/* skip the rest of the "question" part */
ptr += SIZEOF_DNS_QUERY;
res_idx += SIZEOF_DNS_QUERY;
while (nanswers > 0) {
/* skip answer resource record's host name */
ptr = dns_parse_name(ptr);
res_idx = dns_parse_name(p, res_idx);
/* Check for IP address type and Internet class. Others are discarded. */
SMEMCPY(&ans, ptr, SIZEOF_DNS_ANSWER);
pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx);
if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) &&
(ans.len == PP_HTONS(sizeof(ip_addr_t))) ) {
res_idx += SIZEOF_DNS_ANSWER;
/* read the answer resource record's TTL, and maximize it if needed */
entry->ttl = ntohl(ans.ttl);
if (entry->ttl > DNS_MAX_TTL) {
entry->ttl = DNS_MAX_TTL;
}
/* read the IP address after answer resource record's header */
SMEMCPY(&(entry->ipaddr), (ptr + SIZEOF_DNS_ANSWER), sizeof(ip_addr_t));
pbuf_copy_partial(p, &(entry->ipaddr), sizeof(entry->ipaddr), res_idx);
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
ip_addr_debug_print(DNS_DEBUG, (&(entry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
@ -1098,7 +1083,7 @@ dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t
/* deallocate memory and return */
goto memerr;
} else {
ptr = ptr + SIZEOF_DNS_ANSWER + htons(ans.len);
res_idx = SIZEOF_DNS_ANSWER + htons(ans.len);
}
--nanswers;
}

5
src/include/lwip/opt.h
View File

@ -901,11 +901,6 @@
#define DNS_DOES_NAME_CHECK 1
#endif
/** DNS message max. size. Default value is RFC compliant. */
#ifndef DNS_MSG_SIZE
#define DNS_MSG_SIZE 512
#endif
/** DNS_LOCAL_HOSTLIST: Implements a local host-to-address list. If enabled,
* you have to define
* #define DNS_LOCAL_HOSTLIST_INIT {{"host1", 0x123}, {"host2", 0x234}}