Not only is there struct, but also scapy which can craft any packet with ease. A quick Google search shows DNS examples, https://thepacketgeek.com/scapy/building-network-tools/part-09/. Combining asyncio with uvloop also provides very good performance. Ryan Hamel ________________________________ From: John Levine via NANOG <nanog@lists.nanog.org> Sent: Sunday, August 10, 2025 5:56 PM To: nanog@lists.nanog.org <nanog@lists.nanog.org> Cc: John Levine <johnl@iecc.com> Subject: Re: Speaking of DNS server software... Caution: This is an external email and may be malicious. Please take care when clicking links or opening attachments. It appears that William Herrin via NANOG <nanog@lists.nanog.org> said:
Python doesn't work this way. Its memory management is abstracted away from the programmer and the programmer does not control its precise structure. For Python to access a DNS packet, the programmer must pack and unpack an array of bytes using complex software of their own devising. You can't just tell Python, "This is the complex data structure these bytes contain, let me access the data without unpacking it."
The python struct module is pretty fast, since it's written in C. I recently rewrote the abuse.net DNS server in python doing white lies on the fly DNSSEC signing. It's fast enough. R's, John _______________________________________________ NANOG mailing list https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.nanog.org%2Farchives%2Flist%2Fnanog%40lists.nanog.org%2Fmessage%2FBGFDLG24XEHD47QE77ST6LY4OXUMHIKS%2F&data=05%7C02%7Cryan%40rkhtech.org%7C7acd43e68c4640cba83208ddd87271ce%7C81c24bb4f9ec4739ba4d25c42594d996%7C0%7C0%7C638904708244791010%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=VjAtZulg33OR7sZwZBVoRhMmndVN6Lzzm2TISqmU5xM%3D&reserved=0<https://lists.nanog.org/archives/list/nanog@lists.nanog.org/message/BGFDLG24XEHD47QE77ST6LY4OXUMHIKS/>