Split-Horizon DNS Lab Teaches How One Domain Name Returns Two Different Answers

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A new hands-on lab from the Protocol Lab series demonstrates split-horizon DNS, a technique where an authoritative server returns different IP addresses for the same domain name depending on the client's source address. Internal clients on the 10.0.1.0/24 subnet receive a private address, while all external clients receive a public-facing address for the same hostname. The setup uses BIND9's view feature, where the match-clients directive selects the appropriate zone response based on the requester's network. The lab runs entirely in containerized environments using Docker and Containerlab, with no real internet traffic involved, as all addresses fall within RFC 1918 and RFC 5737 documentation ranges. It covers key concepts including view ordering, zone consistency across views, and common use cases such as hiding internal network topology from outside users.

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Baidu's Unlimited-OCR Parses 40-Page PDFs in One Pass With Flat Memory Use

Baidu has released Unlimited-OCR, an open-source model capable of processing multi-page PDFs in a single forward pass without the memory growth that typically plagues OCR pipelines. The model replaces standard attention layers with a mechanism called Reference Sliding Window Attention (R-SWA), which maintains a fixed-size token cache instead of an ever-growing one, keeping memory and latency constant across long documents. With 3 billion total parameters but only 500 million activated via a Mixture-of-Experts architecture, the model runs closer to the cost of a 500M model at inference time. It scored 93.23 on OmniDocBench v1.5, roughly 6.2 points above the DeepSeek-OCR baseline it was trained from, suggesting the efficiency gains did not come at the cost of accuracy. The model is released under an MIT license and requires an NVIDIA GPU with at least 12 GB of VRAM for practical use.

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ProgrammingDEV Community ·

Engineer Streams USB Mouse Over WiFi Using Netevent and Systemd

A developer without a USB-C adapter devised a way to use a USB mouse connected to one machine on a separate laptop over the network. The solution uses netevent, a small Linux tool that captures raw input events from a device and streams them via a pipe to recreate a virtual mouse on the receiving machine. An initial SSH-based one-liner worked but introduced security and reliability concerns, prompting a more robust setup. The author replaced it with a systemd socket-activated service bound exclusively to a Tailscale network interface, ensuring encrypted, authenticated access with no LAN exposure. Additional hardening measures included limiting simultaneous connections to one and using a short-lived dynamic user with only the input group privilege, eliminating the need for root access.

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ProgrammingDEV Community ·

JavaScript Function Types: Key Differences in Hoisting, This, and Usage

JavaScript offers multiple ways to define functions, including declarations, expressions, arrow functions, object methods, constructors, classes, generators, async functions, and IIFEs. Each type differs in important behaviors such as hoisting, how the 'this' keyword is bound, access to the 'arguments' object, and whether the function can be invoked with 'new'. For example, function declarations are fully hoisted and callable before their definition, while arrow functions are not hoisted and inherit 'this' lexically from their surrounding scope. Arrow functions used as object methods can cause bugs because they do not bind 'this' to the owning object, often returning undefined instead. Understanding these distinctions is essential for writing predictable JavaScript and is a common focus area in technical interviews.

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ProgrammingDEV Community ·

PostgreSQL Cursors Slash Export Times by Replacing Random Reads with Sequential Scans

A data pipeline exporting hundreds of gigabytes from PostgreSQL in 2,000-row batches was running far slower than expected, with the bottleneck traced to how the database read data from disk. Using a WHERE id > X LIMIT 2000 pattern caused Postgres to perform up to 2,000 random page lookups per batch via a B-tree index, forcing the disk head to constantly seek across different locations. Switching to a server-side cursor allowed Postgres to scan the heap sequentially, reading each 8KB page exactly once and enabling the OS to prefetch ahead predictably. This change required no schema modifications — only a different query pattern — yet dramatically reduced I/O overhead at scale. However, cursors hold an open transaction for their entire duration, which can block vacuum and inflate write-ahead logs on very large or long-running exports.

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