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Some doc, added URI type resolver

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pull/30/head
Jeroen Domburg 10 years ago
parent 7aa2d227a7
commit b458df915e
1 changed files with 40 additions and 13 deletions
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  1. 53
      user/captdns.c

53
user/captdns.c
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@ -50,7 +50,10 @@ typedef struct __attribute__ ((packed)) {
//after: rdata
} DnsResourceFooter;
typedef struct __attribute__ ((packed)) {
uint16_t prio;
uint16_t weight;
} DnsUriHdr;
#define FLAG_QR (1<<7)
@ -68,9 +71,11 @@ typedef struct __attribute__ ((packed)) {
#define QTYPE_MINFO 14
#define QTYPE_MX 15
#define QTYPE_TXT 16
#define QTYPE_URI 256
#define QCLASS_IN 1
#define QCLASS_ANY 255
#define QCLASS_URI 256
//Function to put unaligned 16-bit network values
@ -95,7 +100,7 @@ static uint16_t ICACHE_FLASH_ATTR ntohs(uint16_t *in) {
}
//Parses a label.
//Parses a label into a C-string containing a dotted
//Returns pointer to start of next fields in packet
static char* ICACHE_FLASH_ATTR labelToStr(char *packet, char *labelPtr, int packetSz, char *res, int resMaxLen) {
int i, j, k;
@ -128,6 +133,7 @@ static char* ICACHE_FLASH_ATTR labelToStr(char *packet, char *labelPtr, int pack
}
//Converts a dotted hostname to the weird label form dns uses.
static char ICACHE_FLASH_ATTR *strToLabel(char *str, char *label, int maxLen) {
char *len=label; //ptr to len byte
char *p=label+1; //ptr to next label byte to be written
@ -148,7 +154,7 @@ static char ICACHE_FLASH_ATTR *strToLabel(char *str, char *label, int maxLen) {
}
//Receive a DNS packet and maybe send a response back
static void ICACHE_FLASH_ATTR captdnsRecv(void* arg, char *pusrdata, unsigned short length) {
struct espconn *conn=(struct espconn *)arg;
char buff[512];
@ -159,8 +165,8 @@ static void ICACHE_FLASH_ATTR captdnsRecv(void* arg, char *pusrdata, unsigned sh
DnsHeader *hdr=(DnsHeader*)p;
DnsHeader *rhdr=(DnsHeader*)&reply[0];
p+=sizeof(DnsHeader);
os_printf("DNS packet: id 0x%X flags 0x%X rcode 0x%X qcnt %d ancnt %d nscount %d arcount %d len %d\n",
ntohs(&hdr->id), hdr->flags, hdr->rcode, ntohs(&hdr->qdcount), ntohs(&hdr->ancount), ntohs(&hdr->nscount), ntohs(&hdr->arcount), length);
// os_printf("DNS packet: id 0x%X flags 0x%X rcode 0x%X qcnt %d ancnt %d nscount %d arcount %d len %d\n",
// ntohs(&hdr->id), hdr->flags, hdr->rcode, ntohs(&hdr->qdcount), ntohs(&hdr->ancount), ntohs(&hdr->nscount), ntohs(&hdr->arcount), length);
//Some sanity checks:
if (length>512) return; //Packet is longer than DNS implementation allows
if (length<sizeof(DnsHeader)) return; //Packet is too short
@ -175,7 +181,7 @@ static void ICACHE_FLASH_ATTR captdnsRecv(void* arg, char *pusrdata, unsigned sh
if (p==NULL) return;
DnsQuestionFooter *qf=(DnsQuestionFooter*)p;
p+=sizeof(DnsQuestionFooter);
os_printf("Q %d (type 0x%X class 0x%X) for %s\n", i, ntohs(&qf->type), ntohs(&qf->class), buff);
os_printf("DNS: Q (type 0x%X class 0x%X) for %s\n", ntohs(&qf->type), ntohs(&qf->class), buff);
if (ntohs(&qf->type)==QTYPE_A) {
//They want to know the IPv4 address of something.
//Build the response.
@ -187,14 +193,17 @@ static void ICACHE_FLASH_ATTR captdnsRecv(void* arg, char *pusrdata, unsigned sh
setn16(&rf->class, QCLASS_IN);
setn32(&rf->ttl, 1);
setn16(&rf->rdlength, 4); //IPv4 addr is 4 bytes;
*rend++=192; //hardcoded :X
*rend++=168;
*rend++=4;
*rend++=1;
//Grab the current IP of the softap interface
struct ip_info info;
wifi_get_ip_info(SOFTAP_IF, &info);
*rend++=ip4_addr1(&info.ip);
*rend++=ip4_addr2(&info.ip);
*rend++=ip4_addr3(&info.ip);
*rend++=ip4_addr4(&info.ip);
setn16(&rhdr->ancount, ntohs(&rhdr->ancount)+1);
os_printf("Added A rec to resp. Resp len is %d\n", (rend-reply));
// os_printf("Added A rec to resp. Resp len is %d\n", (rend-reply));
} else if (ntohs(&qf->type)==QTYPE_NS) {
//Give ns server. Basically is whatever.
//Give ns server. Basically can be whatever we want because it'll get resolved to our IP later anyway.
rend=strToLabel(buff, rend, sizeof(reply)-(rend-reply)); //Add the label
DnsResourceFooter *rf=(DnsResourceFooter *)rend;
rend+=sizeof(DnsResourceFooter);
@ -207,9 +216,27 @@ static void ICACHE_FLASH_ATTR captdnsRecv(void* arg, char *pusrdata, unsigned sh
*rend++='s';
*rend++=0;
setn16(&rhdr->ancount, ntohs(&rhdr->ancount)+1);
os_printf("Added NS rec to resp. Resp len is %d\n", (rend-reply));
// os_printf("Added NS rec to resp. Resp len is %d\n", (rend-reply));
} else if (ntohs(&qf->type)==QTYPE_URI) {
//Give uri to us
rend=strToLabel(buff, rend, sizeof(reply)-(rend-reply)); //Add the label
DnsResourceFooter *rf=(DnsResourceFooter *)rend;
rend+=sizeof(DnsResourceFooter);
DnsUriHdr *uh=(DnsUriHdr *)rend;
rend+=sizeof(DnsUriHdr);
setn16(&rf->type, QTYPE_URI);
setn16(&rf->class, QCLASS_URI);
setn16(&rf->ttl, 1);
setn16(&rf->rdlength, 4+16);
setn16(&uh->prio, 10);
setn16(&uh->weight, 1);
memcpy(rend, "http://esp.local", 16);
rend+=16;
setn16(&rhdr->ancount, ntohs(&rhdr->ancount)+1);
// os_printf("Added NS rec to resp. Resp len is %d\n", (rend-reply));
}
}
//Send the response
espconn_sent(conn, (uint8*)reply, rend-reply);
}

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