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Diffstat (limited to 'core/dnsresolv.inc')
| -rw-r--r-- | core/dnsresolv.inc | 389 |
1 files changed, 0 insertions, 389 deletions
diff --git a/core/dnsresolv.inc b/core/dnsresolv.inc deleted file mode 100644 index c2c429cb..00000000 --- a/core/dnsresolv.inc +++ /dev/null @@ -1,389 +0,0 @@ -; -*- fundamental -*- -; ----------------------------------------------------------------------- -; -; Copyright 2004-2008 H. Peter Anvin - All Rights Reserved -; -; This program is free software; you can redistribute it and/or modify -; it under the terms of the GNU General Public License as published by -; the Free Software Foundation, Inc., 53 Temple Place Ste 330, -; Bostom MA 02111-1307, USA; either version 2 of the License, or -; (at your option) any later version; incorporated herein by reference. -; -; ----------------------------------------------------------------------- - -; -; dnsresolv.inc -; -; Very simple DNS resolver (assumes recursion-enabled DNS server; -; this should be the normal thing for client-serving DNS servers.) -; - -DNS_PORT equ htons(53) ; Default DNS port -DNS_MAX_PACKET equ 512 ; Defined by protocol -; TFTP uses the range 49152-57343 -DNS_LOCAL_PORT equ htons(60053) ; All local DNS queries come from this port # -DNS_MAX_SERVERS equ 4 ; Max no of DNS servers - - section .text - -; -; Turn a string in DS:SI into a DNS "label set" in ES:DI. -; On return, DI points to the first byte after the label set, -; and SI to the terminating byte. -; -; On return, DX contains the number of dots encountered. -; -dns_mangle: - push ax - push bx - xor dx,dx -.isdot: - inc dx - xor al,al - mov bx,di - stosb -.getbyte: - lodsb - and al,al - jz .endstring - cmp al,':' - jz .endstring - cmp al,'.' - je .isdot - inc byte [es:bx] - stosb - jmp .getbyte -.endstring: - dec si - dec dx ; We always counted one high - cmp byte [es:bx],0 - jz .done - xor al,al - stosb -.done: - pop bx - pop ax - ret - -; -; Compare two sets of DNS labels, in DS:SI and ES:DI; the one in SI -; is allowed pointers relative to a packet in DNSRecvBuf. -; -; Assumes DS == ES. ZF = 1 if same; no registers changed. -; (Note: change reference to [di] to [es:di] to remove DS == ES assumption) -; -dns_compare: - pusha -%if 0 - -.label: - lodsb - cmp al,0C0h - jb .noptr - and al,03Fh ; Get pointer value - mov ah,al ; ... in network byte order! - lodsb - mov si,DNSRecvBuf - add si,ax - jmp .label -.noptr: - cmp al,[di] - jne .done ; Mismatch - inc di - movzx cx,al ; End label? - and cx,cx ; ZF = 1 if match - jz .done - - ; We have a string of bytes that need to match now - repe cmpsb - je .label - -.done: -%else - xor ax,ax -%endif - popa - ret - -; -; Skip past a DNS label set in DS:SI. -; -dns_skiplabel: - push ax - xor ax,ax ; AH == 0 -.loop: - lodsb - cmp al,0C0h ; Pointer? - jae .ptr - and al,al - jz .done - add si,ax - jmp .loop -.ptr: - inc si ; Pointer is two bytes -.done: - pop ax - ret - - ; DNS header format - struc dnshdr -.id: resw 1 -.flags: resw 1 -.qdcount: resw 1 -.ancount: resw 1 -.nscount: resw 1 -.arcount: resw 1 - endstruc - - ; DNS query - struc dnsquery -.qtype: resw 1 -.qclass: resw 1 - endstruc - - ; DNS RR - struc dnsrr -.type: resw 1 -.class: resw 1 -.ttl: resd 1 -.rdlength: resw 1 -.rdata: equ $ - endstruc - - section .bss2 - alignb 2 -DNSSendBuf resb DNS_MAX_PACKET -DNSRecvBuf resb DNS_MAX_PACKET -LocalDomain resb 256 ; Max possible length -DNSServers resd DNS_MAX_SERVERS - - section .data -pxe_udp_write_pkt_dns: -.status: dw 0 ; Status -.sip: dd 0 ; Server IP -.gip: dd 0 ; Gateway IP -.lport: dw DNS_LOCAL_PORT ; Local port -.rport: dw DNS_PORT ; Remote port -.buffersize: dw 0 ; Size of packet -.buffer: dw DNSSendBuf, 0 ; off, seg of buffer - -pxe_udp_read_pkt_dns: -.status: dw 0 ; Status -.sip: dd 0 ; Source IP -.dip: dd 0 ; Destination (our) IP -.rport: dw DNS_PORT ; Remote port -.lport: dw DNS_LOCAL_PORT ; Local port -.buffersize: dw DNS_MAX_PACKET ; Max packet size -.buffer: dw DNSRecvBuf, 0 ; off, seg of buffer - -LastDNSServer dw DNSServers - -; Actual resolver function -; Points to a null-terminated or :-terminated string in DS:SI -; and returns the name in EAX if it exists and can be found. -; If EAX = 0 on exit, the lookup failed. -; -; No segment assumptions permitted. -; - section .text -dns_resolv: - push ds - push es - push di - push bx - push cx - push dx - - push cs - pop es ; ES <- CS - - ; First, build query packet - mov di,DNSSendBuf+dnshdr.flags - inc word [es:di-2] ; New query ID - mov ax,htons(0100h) ; Recursion requested - stosw - mov ax,htons(1) ; One question - stosw - xor ax,ax ; No answers, NS or ARs - stosw - stosw - stosw - - call dns_mangle ; Convert name to DNS labels - - push cs ; DS <- CS - pop ds - - push si ; Save pointer to after DNS string - - ; Initialize... - mov eax,[MyIP] - mov [pxe_udp_read_pkt_dns.dip],eax - - and dx,dx - jnz .fqdn ; If we have dots, assume it's FQDN - dec di ; Remove final null - mov si,LocalDomain - call strcpy ; Uncompressed DNS label set so it ends in null -.fqdn: - - mov ax,htons(1) - stosw ; QTYPE = 1 = A - stosw ; QCLASS = 1 = IN - - sub di,DNSSendBuf - mov [pxe_udp_write_pkt_dns.buffersize],di - - ; Now, send it to the nameserver(s) - ; Outer loop: exponential backoff - ; Inner loop: scan the various DNS servers - - mov bx,TimeoutTable -.backoff: - movzx dx,byte [bx] - mov si,DNSServers -.servers: - cmp si,[LastDNSServer] - jb .moreservers - -.nomoreservers: - inc bx - cmp bx,TimeoutTableEnd - jb .backoff - - xor eax,eax ; Nothing... -.done: - pop si - pop dx - pop cx - pop bx - pop di - pop es - pop ds - ret - -.moreservers: - lodsd ; EAX <- next server - push si - push bx - push cx - push dx - - mov word [pxe_udp_write_pkt_dns.status],0 - - mov [pxe_udp_write_pkt_dns.sip],eax - mov [pxe_udp_read_pkt_dns.sip],eax - xor eax,[MyIP] - and eax,[Netmask] - jz .nogw - mov eax,[Gateway] -.nogw: - mov [pxe_udp_write_pkt_dns.gip],eax - - mov di,pxe_udp_write_pkt_dns - mov bx,PXENV_UDP_WRITE - call pxenv - jc .timeout ; Treat failed transmit as timeout - cmp word [pxe_udp_write_pkt_dns.status],0 - jne .timeout - - mov cx,[BIOS_timer] -.waitrecv: - mov ax,[BIOS_timer] - sub ax,cx - cmp ax,dx - jae .timeout - - mov word [pxe_udp_read_pkt_dns.status],0 - mov word [pxe_udp_read_pkt_dns.buffersize],DNS_MAX_PACKET - mov di,pxe_udp_read_pkt_dns - mov bx,PXENV_UDP_READ - call pxenv - and ax,ax - jnz .waitrecv - cmp [pxe_udp_read_pkt_dns.status],ax - jnz .waitrecv - - ; Got a packet, deal with it... - mov si,DNSRecvBuf - lodsw - cmp ax,[DNSSendBuf] ; ID - jne .waitrecv ; Not ours - - lodsw ; flags - xor al,80h ; Query#/Answer bit - test ax,htons(0F80Fh) - jnz .badness - - lodsw - xchg ah,al ; ntohs - mov cx,ax ; Questions echoed - lodsw - xchg ah,al ; ntohs - push ax ; Replies - lodsw ; NS records - lodsw ; Authority records - - jcxz .qskipped -.skipq: - call dns_skiplabel ; Skip name - add si,4 ; Skip question trailer - loop .skipq - -.qskipped: - pop cx ; Number of replies - jcxz .badness - -.parseanswer: - mov di,DNSSendBuf+dnshdr_size - call dns_compare - pushf - call dns_skiplabel - mov ax,[si+8] ; RDLENGTH - xchg ah,al ; ntohs - popf - jnz .notsame - cmp dword [si],htons(1)*0x10001 ; TYPE = A, CLASS = IN? - jne .notsame - cmp ax,4 ; RDLENGTH = 4? - jne .notsame - ; - ; We hit paydirt here... - ; - mov eax,[si+10] -.gotresult: - add sp,8 ; Drop timeout information - jmp .done - -.notsame: - add si,10 - add si,ax - loop .parseanswer - -.badness: - ; We got back no data from this server. - ; Unfortunately, for a recursive, non-authoritative - ; query there is no such thing as an NXDOMAIN reply, - ; which technically means we can't draw any - ; conclusions. However, in practice that means the - ; domain doesn't exist. If this turns out to be a - ; problem, we may want to add code to go through all - ; the servers before giving up. - - ; If the DNS server wasn't capable of recursion, and - ; isn't capable of giving us an authoritative reply - ; (i.e. neither AA or RA set), then at least try a - ; different setver... - - test word [DNSRecvBuf+dnshdr.flags],htons(0480h) - jz .timeout - - xor eax,eax - jmp .gotresult - -.timeout: - pop dx - pop cx - pop bx - pop si - jmp .servers |