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Minor changes on DNS client. Coding style & add "response" checking

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This commit is contained in:
fbernon 2007-11-18 15:51:34 +00:00
parent 92401faa72
commit 4e398e2aa9
2 changed files with 62 additions and 45 deletions
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77
src/core/dns.c
View File

@ -68,7 +68,6 @@
/** @todo: secondary server support */
/** @todo: pbuf chain not yet supported */
/** @todo: improve answer parsing, more checkings... */
/** @todo: possible alignment problems to access to dns_answer fields? */
/*-----------------------------------------------------------------------------
* Includes
@ -132,31 +131,6 @@
#define DNS_STATE_ASKING 2
#define DNS_STATE_DONE 3
/* DNS field TYPE used for "Resource Records" */
#define DNS_RRTYPE_A 1 /* a host address */
#define DNS_RRTYPE_NS 2 /* an authoritative name server */
#define DNS_RRTYPE_MD 3 /* a mail destination (Obsolete - use MX) */
#define DNS_RRTYPE_MF 4 /* a mail forwarder (Obsolete - use MX) */
#define DNS_RRTYPE_CNAME 5 /* the canonical name for an alias */
#define DNS_RRTYPE_SOA 6 /* marks the start of a zone of authority */
#define DNS_RRTYPE_MB 7 /* a mailbox domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_MG 8 /* a mail group member (EXPERIMENTAL) */
#define DNS_RRTYPE_MR 9 /* a mail rename domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_NULL 10 /* a null RR (EXPERIMENTAL) */
#define DNS_RRTYPE_WKS 11 /* a well known service description */
#define DNS_RRTYPE_PTR 12 /* a domain name pointer */
#define DNS_RRTYPE_HINFO 13 /* host information */
#define DNS_RRTYPE_MINFO 14 /* mailbox or mail list information */
#define DNS_RRTYPE_MX 15 /* mail exchange */
#define DNS_RRTYPE_TXT 16 /* text strings */
/* DNS field CLASS used for "Resource Records" */
#define DNS_RRCLASS_IN 1 /* the Internet */
#define DNS_RRCLASS_CS 2 /* the CSNET class (Obsolete - used only for examples in some obsolete RFCs) */
#define DNS_RRCLASS_CH 3 /* the CHAOS class */
#define DNS_RRCLASS_HS 4 /* Hesiod [Dyer 87] */
#define DNS_RRCLASS_FLUSH 0x800 /* Flush bit */
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
@ -176,6 +150,22 @@ PACK_STRUCT_END
# include "arch/epstruct.h"
#endif
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
PACK_STRUCT_BEGIN
/** DNS query message structure */
struct dns_query {
/* DNS query record starts with either a domain name or a pointer
to a name already present somewhere in the packet. */
u16_t type;
u16_t class;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/epstruct.h"
#endif
#ifdef PACK_STRUCT_USE_INCLUDES
# include "arch/bpstruct.h"
#endif
@ -188,7 +178,6 @@ struct dns_answer {
u16_t class;
u32_t ttl;
u16_t len;
struct ip_addr ipaddr;
} PACK_STRUCT_STRUCT;
PACK_STRUCT_END
#ifdef PACK_STRUCT_USE_INCLUDES
@ -230,9 +219,6 @@ static struct udp_pcb *dns_pcb;
static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
static u8_t dns_seqno;
/* DNS request termination sequence: zero(1)+type(2)+class(2) */
static unsigned char dns_endquery[] = {0,0,1,0,1};
/**
* Initialize the resolver and configure which DNS server to use for queries.
*
@ -373,6 +359,7 @@ static err_t
dns_send(const char* name, u8_t id)
{
struct dns_hdr *hdr;
struct dns_query *qry;
struct pbuf *p;
char *query, *nptr;
const char *pHostname;
@ -381,8 +368,9 @@ dns_send(const char* name, u8_t id)
LWIP_DEBUGF(DNS_DEBUG, ("dns_send: \"%s\": request\n", name));
/* if here, we have either a new query or a retry on a previous query to process */
p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dns_hdr)+DNS_MAX_NAME_LENGTH+sizeof(dns_endquery), PBUF_RAM);
p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dns_hdr)+DNS_MAX_NAME_LENGTH+sizeof(struct dns_query), PBUF_RAM);
if (p) {
/* fill dns header */
hdr = (struct dns_hdr *)p->payload;
memset(hdr, 0, sizeof(struct dns_hdr));
hdr->id = htons(id);
@ -391,6 +379,7 @@ dns_send(const char* name, u8_t id)
query = (char *)hdr + sizeof(struct dns_hdr);
pHostname = name;
--pHostname;
/* convert hostname into suitable query format. */
do {
++pHostname;
@ -403,11 +392,15 @@ dns_send(const char* name, u8_t id)
}
*nptr = n;
} while(*pHostname != 0);
*query++='\0';
memcpy( query, dns_endquery, sizeof(dns_endquery));
/* fill dns query */
qry = (struct dns_query *)query;
qry->type = htons(DNS_RRTYPE_A);
qry->class = htons(DNS_RRCLASS_IN);
/* resize pbuf to the exact dns query */
pbuf_realloc(p, (query+sizeof(dns_endquery))-((char*)(p->payload)));
pbuf_realloc(p, (query+sizeof(struct dns_query))-((char*)(p->payload)));
/* send dns packet */
udp_send(dns_pcb, p);
@ -487,8 +480,8 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
{
u8_t i;
char *pHostname;
struct dns_answer *ans;
struct dns_hdr *hdr;
struct dns_answer *ans;
struct dns_table_entry *pEntry;
u8_t nquestions, nanswers;
@ -513,7 +506,7 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
nanswers = htons(hdr->numanswers);
/* Check for error. If so, call callback to inform. */
if ((pEntry->err != 0) || (nquestions != 1)) {
if (((hdr->flags1 & DNS_FLAG1_RESPONSE)==0) ||(pEntry->err != 0) || (nquestions != 1)) {
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name));
/* call specified callback function if provided */
if (pEntry->found)
@ -526,19 +519,17 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
/* Skip the name in the "question" part. This should really be checked
agains the name in the question, to be sure that they match. */
pHostname = (char *) dns_parse_name((unsigned char *)p->payload + sizeof(struct dns_hdr)) + 4/*type(2)+class(2)*/;
pHostname = (char *) dns_parse_name((unsigned char *)p->payload + sizeof(struct dns_hdr)) + sizeof(struct dns_query);
while(nanswers > 0) {
/* skip answer resource record's host name */
pHostname = (char *) dns_parse_name((unsigned char *)pHostname);
/* TODO: isn't it any problem to access to dns_answer fields since pHostname's length can be unaligned? */
ans = (struct dns_answer *)pHostname;
/* Check for IP address type and Internet class. Others are discarded. */
if((ntohs(ans->type) == DNS_RRTYPE_A) && (ntohs(ans->class) == DNS_RRCLASS_IN) && (ntohs(ans->len) == 4/*IPv4 address*/) ) {
/* TODO: we should really check that this IP address is the one we want. */
pEntry->ipaddr = ans->ipaddr;
ans = (struct dns_answer *)pHostname;
if((ntohs(ans->type) == DNS_RRTYPE_A) && (ntohs(ans->class) == DNS_RRCLASS_IN) && (ntohs(ans->len) == sizeof(struct ip_addr)) ) {
/* read the IP address after answer resource record's header */
pEntry->ipaddr = (*((struct ip_addr*)(ans+1)));
LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name));
ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr)));
LWIP_DEBUGF(DNS_DEBUG, ("\n"));
@ -547,7 +538,7 @@ dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16
(*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg);
return;
} else {
pHostname = pHostname + 10 /*type(2)+class(2)+ttl(4)+len(2)*/ + htons(ans->len);
pHostname = pHostname + sizeof(struct dns_answer) + htons(ans->len);
}
--nanswers;
}

30
src/include/lwip/dns.h
View File

@ -44,7 +44,32 @@
#endif
/** DNS message max. size */
#define DNS_MSG_SIZE 512
#define DNS_MSG_SIZE 512
/** DNS field TYPE used for "Resource Records" */
#define DNS_RRTYPE_A 1 /* a host address */
#define DNS_RRTYPE_NS 2 /* an authoritative name server */
#define DNS_RRTYPE_MD 3 /* a mail destination (Obsolete - use MX) */
#define DNS_RRTYPE_MF 4 /* a mail forwarder (Obsolete - use MX) */
#define DNS_RRTYPE_CNAME 5 /* the canonical name for an alias */
#define DNS_RRTYPE_SOA 6 /* marks the start of a zone of authority */
#define DNS_RRTYPE_MB 7 /* a mailbox domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_MG 8 /* a mail group member (EXPERIMENTAL) */
#define DNS_RRTYPE_MR 9 /* a mail rename domain name (EXPERIMENTAL) */
#define DNS_RRTYPE_NULL 10 /* a null RR (EXPERIMENTAL) */
#define DNS_RRTYPE_WKS 11 /* a well known service description */
#define DNS_RRTYPE_PTR 12 /* a domain name pointer */
#define DNS_RRTYPE_HINFO 13 /* host information */
#define DNS_RRTYPE_MINFO 14 /* mailbox or mail list information */
#define DNS_RRTYPE_MX 15 /* mail exchange */
#define DNS_RRTYPE_TXT 16 /* text strings */
/** DNS field CLASS used for "Resource Records" */
#define DNS_RRCLASS_IN 1 /* the Internet */
#define DNS_RRCLASS_CS 2 /* the CSNET class (Obsolete - used only for examples in some obsolete RFCs) */
#define DNS_RRCLASS_CH 3 /* the CHAOS class */
#define DNS_RRCLASS_HS 4 /* Hesiod [Dyer 87] */
#define DNS_RRCLASS_FLUSH 0x800 /* Flush bit */
/* enumerated list of possible result values returned by dns_gethostname() */
typedef enum dns_result {
@ -53,6 +78,7 @@ typedef enum dns_result {
DNS_COMPLETE
}DNS_RESULT;
/* initializes the resolver */
err_t dns_init(void);
@ -68,7 +94,7 @@ u32_t dns_getserver(u8_t numdns);
/* returns IP for host 'name' only if already in table */
u32_t dns_lookup(const char *name);
/* resolove a host 'name' in ip address */
/* resolves a host 'name' in ip address */
DNS_RESULT dns_gethostbyname(const char *hostName, struct ip_addr *addr,
void (*found)(const char *name, struct ip_addr *ipaddr, void *arg),
void *arg);