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Helper library for parsing valid/invalid/broken/malformed DNS packets


This is a helper library intended to be included within other projects repositories as a submodule to help them parse DNS packets. It will parse as much as possible and will indicate where and what failed if any.

Supported RFCs:

  • todo


Here is a short example how to use this library, for a more complete program check hexdns2text/hexdns2text.c.

#include "omg-dns/omg_dns.h"
#include <stdio.h>

struct context {
    size_t num_rr;
    size_t num_label;

static int label_callback(const omg_dns_label_t* label, void* vp) {
    struct context* context = (struct context*)vp;

    printf("  label %lu:\n", context->num_label++);
    if (omg_dns_label_is_end(label))
        printf("    end: yes\n");
    else if (!omg_dns_label_is_complete(label))
        printf("    incomplete: yes\n");
    else if (omg_dns_label_have_offset(label))
        printf("    offset: %d\n", omg_dns_label_offset(label));
    else if (omg_dns_label_have_extension_bits(label))
        printf("    extension_bits: %02x\n", omg_dns_label_extension_bits(label));

    return OMG_DNS_OK;

static int rr_callback(int ret, const omg_dns_rr_t* rr, void* vp) {
    struct context* context = (struct context*)vp;

    printf("  rr %lu:\n", context->num_rr++);
    printf("    question: %s\n", omg_dns_rr_is_question(rr) ? "yes" : "no");
    if (omg_dns_rr_have_type(rr))
        printf("    type: %u\n", omg_dns_rr_type(rr));

    return OMG_DNS_OK;

int main(void) {
    omg_dns_t dns = OMG_DNS_T_INIT;
    struct context context = { 0, 0 };
    uint8_t packet[] = { ... raw dns packet as byte array ... };

    omg_dns_set_rr_callback(&dns, rr_callback, (void*)&context);
    omg_dns_set_label_callback(&dns, label_callback, (void*)&context);
    omg_dns_parse(&dns, packet, sizeof(packet));

    if (omg_dns_have_id(&dns))
        printf("id: %u\n", omg_dns_id(&dns));

    return 0;

git submodule

git submodule init
git submodule add src/omg-dns

program_SOURCES += omg-dns/omg_dns.c
dist_program_SOURCES += omg-dns/omg_dns.h


Jerry Lundström


Copyright (c) 2017, OARC, Inc. All rights reserved.

This file is part of omg-dns.

omg-dns is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

omg-dns is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with omg-dns. If not, see