captdns.c File Reference

#include <esp8266.h>
#include <lwip/ip.h>
#include <lwip/udp.h>
#include <lwip/tcp_impl.h>
#include <netif/etharp.h>
#include <lwip/netif.h>
#include <lwip/lwip_napt.h>
#include <lwip/dns.h>
#include <lwip/app/dhcpserver.h>
#include <lwip/opt.h>
#include <espconn.h>

Include dependency graph for captdns.c:

Go to the source code of this file.

Macros
#define	DNS_LEN   512
#define	FLAG_QR   (1<<7)
#define	FLAG_AA   (1<<2)
#define	FLAG_TC   (1<<1)
#define	FLAG_RD   (1<<0)
#define	QTYPE_A   1
#define	QTYPE_NS   2
#define	QTYPE_CNAME   5
#define	QTYPE_SOA   6
#define	QTYPE_WKS   11
#define	QTYPE_PTR   12
#define	QTYPE_HINFO   13
#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

Functions
struct	__attribute__ ((packed))
static void ICACHE_FLASH_ATTR	setn16 (void *pp, int16_t n)
static void ICACHE_FLASH_ATTR	setn32 (void *pp, int32_t n)
static uint16_t ICACHE_FLASH_ATTR	my_ntohs (uint16_t *in)
static char *ICACHE_FLASH_ATTR	labelToStr (char *packet, char *labelPtr, int packetSz, char *res, int resMaxLen)
static char ICACHE_FLASH_ATTR *	strToLabel (char *str, char *label, int maxLen)
static void ICACHE_FLASH_ATTR	captdnsRecv (void *arg, char *pusrdata, unsigned short length)
void ICACHE_FLASH_ATTR	captdnsInit (void)
void ICACHE_FLASH_ATTR	captdnsStop (void)

Variables
static struct espconn	conn
	DnsHeader
	DnsLabel
	DnsQuestionFooter
	DnsResourceFooter
	DnsUriHdr

Macro Definition Documentation

DNS_LEN

#define DNS_LEN   512

Definition at line 47 of file captdns.c.

Referenced by captdnsRecv().

FLAG_AA

#define FLAG_AA   (1<<2)

Definition at line 93 of file captdns.c.

FLAG_QR

#define FLAG_QR   (1<<7)

Definition at line 92 of file captdns.c.

Referenced by captdnsRecv().

FLAG_RD

#define FLAG_RD   (1<<0)

Definition at line 95 of file captdns.c.

FLAG_TC

#define FLAG_TC   (1<<1)

Definition at line 94 of file captdns.c.

Referenced by captdnsRecv().

QCLASS_ANY

#define QCLASS_ANY   255

Definition at line 110 of file captdns.c.

QCLASS_IN

#define QCLASS_IN   1

Definition at line 109 of file captdns.c.

Referenced by captdnsRecv().

QCLASS_URI

#define QCLASS_URI   256

Definition at line 111 of file captdns.c.

Referenced by captdnsRecv().

QTYPE_A

#define QTYPE_A   1

Definition at line 97 of file captdns.c.

Referenced by captdnsRecv().

QTYPE_CNAME

#define QTYPE_CNAME   5

Definition at line 99 of file captdns.c.

QTYPE_HINFO

#define QTYPE_HINFO   13

Definition at line 103 of file captdns.c.

QTYPE_MINFO

#define QTYPE_MINFO   14

Definition at line 104 of file captdns.c.

QTYPE_MX

#define QTYPE_MX   15

Definition at line 105 of file captdns.c.

QTYPE_NS

#define QTYPE_NS   2

Definition at line 98 of file captdns.c.

Referenced by captdnsRecv().

QTYPE_PTR

#define QTYPE_PTR   12

Definition at line 102 of file captdns.c.

QTYPE_SOA

#define QTYPE_SOA   6

Definition at line 100 of file captdns.c.

QTYPE_TXT

#define QTYPE_TXT   16

Definition at line 106 of file captdns.c.

QTYPE_URI

#define QTYPE_URI   256

Definition at line 107 of file captdns.c.

Referenced by captdnsRecv().

QTYPE_WKS

#define QTYPE_WKS   11

Definition at line 101 of file captdns.c.

Function Documentation

__attribute__()

struct __attribute__

(

(packed)

)

Definition at line 53 of file captdns.c.

Referenced by espconn_sendto().

                                        {
    uint16_t id;
    uint8_t flags;
    uint8_t rcode;
    uint16_t qdcount;
    uint16_t ancount;
    uint16_t nscount;
    uint16_t arcount;
} DnsHeader;

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captdnsInit()

void ICACHE_FLASH_ATTR captdnsInit

(

void

)

Definition at line 344 of file captdns.c.

References captdnsRecv(), espconn_create(), espconn_regist_recvcb(), ESPCONN_UDP, _esp_udp::local_port, espconn::proto, espconn::type, and espconn::udp.

Referenced by captdnsRecv().

                                         {
    static esp_udp udpconn;
    conn.type=ESPCONN_UDP;
    conn.proto.udp=&udpconn;
    conn.proto.udp->local_port = 53;
    espconn_regist_recvcb(&conn, captdnsRecv);
    espconn_create(&conn);
}

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captdnsRecv()

static void ICACHE_FLASH_ATTR captdnsRecv ( void *  arg, char *  pusrdata, unsigned short  length  )

static

Definition at line 192 of file captdns.c.

References captdnsInit(), conn, DNS_LEN, DnsHeader, DnsQuestionFooter, DnsResourceFooter, DnsUriHdr, espconn_get_connection_info(), ESPCONN_OK, espconn_sendto(), FLAG_QR, FLAG_TC, htons, ICACHE_FLASH_ATTR, INADDR_ANY, ip_info::ip, ip4_addr1, ip4_addr2, ip4_addr3, ip4_addr4, labelToStr(), memcpy, memset, my_ntohs(), NULL, espconn::proto, QCLASS_IN, QCLASS_URI, QTYPE_A, QTYPE_NS, QTYPE_URI, _esp_udp::remote_ip, _remot_info::remote_ip, _esp_udp::remote_port, _remot_info::remote_port, setn16(), setn32(), SOFTAP_IF, strToLabel(), espconn::udp, and wifi_get_ip_info().

Referenced by captdnsInit().

                                                                                            {
    struct espconn *conn=(struct espconn *)arg;
#else
static void ICACHE_FLASH_ATTR captdnsRecv(struct sockaddr_in *premote_addr, char *pusrdata, unsigned short length) {
#endif
    char buff[DNS_LEN];
    char reply[DNS_LEN];
    int i;
    char *rend=&reply[length];
    char *p=pusrdata;
    DnsHeader *hdr=(DnsHeader*)p;
    DnsHeader *rhdr=(DnsHeader*)&reply[0];
    p+=sizeof(DnsHeader);
//  httpd_printf("DNS packet: id 0x%X flags 0x%X rcode 0x%X qcnt %d ancnt %d nscount %d arcount %d len %d\n", 
//      my_ntohs(&hdr->id), hdr->flags, hdr->rcode, my_ntohs(&hdr->qdcount), my_ntohs(&hdr->ancount), my_ntohs(&hdr->nscount), my_ntohs(&hdr->arcount), length);
    //Some sanity checks:
    if (length>DNS_LEN) return;                                 //Packet is longer than DNS implementation allows
    if (length<sizeof(DnsHeader)) return;                       //Packet is too short
    if (hdr->ancount || hdr->nscount || hdr->arcount) return;   //this is a reply, don't know what to do with it
    if (hdr->flags&FLAG_TC) return;                             //truncated, can't use this
    //Reply is basically the request plus the needed data
    memcpy(reply, pusrdata, length);
    rhdr->flags|=FLAG_QR;
    for (i=0; i<my_ntohs(&hdr->qdcount); i++) {
        //Grab the labels in the q string
        p=labelToStr(pusrdata, p, length, buff, sizeof(buff));
        if (p==NULL) return;
        DnsQuestionFooter *qf=(DnsQuestionFooter*)p;
        p+=sizeof(DnsQuestionFooter);
//      httpd_printf("DNS: Q (type 0x%X class 0x%X) for %s\n", my_ntohs(&qf->type), my_ntohs(&qf->class), buff);
        if (my_ntohs(&qf->type)==QTYPE_A) {
            //They want to know the IPv4 address of something.
            //Build the response.
            rend=strToLabel(buff, rend, sizeof(reply)-(rend-reply)); //Add the label
            if (rend==NULL) return;
            DnsResourceFooter *rf=(DnsResourceFooter *)rend;
            rend+=sizeof(DnsResourceFooter);
            setn16(&rf->type, QTYPE_A);
            setn16(&rf->class, QCLASS_IN);
            setn32(&rf->ttl, 0);
            setn16(&rf->rdlength, 4); //IPv4 addr is 4 bytes;
            //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, my_ntohs(&rhdr->ancount)+1);
//          httpd_printf("Added A rec to resp. Resp len is %d\n", (rend-reply));
        } else if (my_ntohs(&qf->type)==QTYPE_NS) {
            //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);
            setn16(&rf->type, QTYPE_NS);
            setn16(&rf->class, QCLASS_IN);
            setn16(&rf->ttl, 0);
            setn16(&rf->rdlength, 4);
            *rend++=2;
            *rend++='n';
            *rend++='s';
            *rend++=0;
            setn16(&rhdr->ancount, my_ntohs(&rhdr->ancount)+1);
//          httpd_printf("Added NS rec to resp. Resp len is %d\n", (rend-reply));
        } else if (my_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, 0);
            setn16(&rf->rdlength, 4+16);
            setn16(&uh->prio, 10);
            setn16(&uh->weight, 1);
            memcpy(rend, "http://esp.nonet", 16);
            rend+=16;
            setn16(&rhdr->ancount, my_ntohs(&rhdr->ancount)+1);
//          httpd_printf("Added NS rec to resp. Resp len is %d\n", (rend-reply));
        }
    }
    //Send the response
#ifndef FREERTOS
    remot_info *remInfo=NULL;
    //Send data to port/ip it came from, not to the ip/port we listen on.
    if (espconn_get_connection_info(conn, &remInfo, 0)==ESPCONN_OK) {
        conn->proto.udp->remote_port=remInfo->remote_port;
        memcpy(conn->proto.udp->remote_ip, remInfo->remote_ip, sizeof(remInfo->remote_ip));
    }
    espconn_sendto(conn, (uint8*)reply, rend-reply);
#else
    sendto(sockFd,(uint8*)reply, rend-reply, 0, (struct sockaddr *)premote_addr, sizeof(struct sockaddr_in));
#endif
}

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captdnsStop()

void ICACHE_FLASH_ATTR captdnsStop

(

void

)

Definition at line 353 of file captdns.c.

References espconn_delete().

                                         {
    espconn_delete(&conn);
}

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labelToStr()

static char* ICACHE_FLASH_ATTR labelToStr ( char *  packet, char *  labelPtr, int  packetSz, char *  res, int  resMaxLen  )

static

Definition at line 138 of file captdns.c.

References my_ntohs(), and NULL.

Referenced by captdnsRecv().

                                                                                                                {
    int i, j, k;
    char *endPtr=NULL;
    i=0;
    do {
        if ((*labelPtr&0xC0)==0) {
            j=*labelPtr++; //skip past length
            //Add separator period if there already is data in res
            if (i<resMaxLen && i!=0) res[i++]='.';
            //Copy label to res
            for (k=0; k<j; k++) {
                if ((labelPtr-packet)>packetSz) return NULL;
                if (i<resMaxLen) res[i++]=*labelPtr++;
            }
        } else if ((*labelPtr&0xC0)==0xC0) {
            //Compressed label pointer
            endPtr=labelPtr+2;
            int offset=my_ntohs(((uint16_t *)labelPtr))&0x3FFF;
            //Check if offset points to somewhere outside of the packet
            if (offset>packetSz) return NULL;
            labelPtr=&packet[offset];
        }
        //check for out-of-bound-ness
        if ((labelPtr-packet)>packetSz) return NULL;
    } while (*labelPtr!=0);
    res[i]=0; //zero-terminate
    if (endPtr==NULL) endPtr=labelPtr+1;
    return endPtr;
}

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my_ntohs()

static uint16_t ICACHE_FLASH_ATTR my_ntohs ( uint16_t *  in )

static

Definition at line 130 of file captdns.c.

Referenced by captdnsRecv(), and labelToStr().

                                                         {
    char *p=(char*)in;
    return ((p[0]<<8)&0xff00)|(p[1]&0xff);
}

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setn16()

static void ICACHE_FLASH_ATTR setn16 ( void *  pp, int16_t  n  )

static

Definition at line 115 of file captdns.c.

Referenced by captdnsRecv().

                                                          {
    char *p=pp;
    *p++=(n>>8);
    *p++=(n&0xff);
}

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setn32()

static void ICACHE_FLASH_ATTR setn32 ( void *  pp, int32_t  n  )

static

Definition at line 122 of file captdns.c.

Referenced by captdnsRecv().

                                                          {
    char *p=pp;
    *p++=(n>>24)&0xff;
    *p++=(n>>16)&0xff;
    *p++=(n>>8)&0xff;
    *p++=(n&0xff);
}

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strToLabel()

static char ICACHE_FLASH_ATTR* strToLabel ( char *  str, char *  label, int  maxLen  )

static

Definition at line 170 of file captdns.c.

Referenced by captdnsRecv().

                                                                              {
    char *len=label; //ptr to len byte
    char *p=label+1; //ptr to next label byte to be written
    while (1) {
        if (*str=='.' || *str==0) {
            *len=((p-len)-1);   //write len of label bit
            len=p;              //pos of len for next part
            p++;                //data ptr is one past len
            if (*str==0) break; //done
            str++;
        } else {
            *p++=*str++;    //copy byte
//          if ((p-label)>maxLen) return NULL;  //check out of bounds
        }
    }
    *len=0;
    return p; //ptr to first free byte in resp
}

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Variable Documentation

conn

struct espconn conn

static

Definition at line 50 of file captdns.c.

Referenced by captdnsRecv(), httpdConnectCb(), httpdDisconCb(), httpdFindConnData(), httpdReconCb(), httpdRecvCb(), and httpdSentCb().

DnsHeader

DnsHeader

Definition at line 61 of file captdns.c.

Referenced by captdnsRecv().

DnsLabel

DnsLabel

Definition at line 67 of file captdns.c.

DnsQuestionFooter

DnsQuestionFooter

Definition at line 74 of file captdns.c.

Referenced by captdnsRecv().

DnsResourceFooter

DnsResourceFooter

Definition at line 84 of file captdns.c.

Referenced by captdnsRecv().

DnsUriHdr

DnsUriHdr

Definition at line 89 of file captdns.c.

Referenced by captdnsRecv().