Fix broker disconnect to better handle SIGPIPE

[dgarske]

No description provided.

[wolfSSL-Fenrir-bot]

Fenrir Automated Review — PR #548

Scan targets checked: wolfmqtt-bugs, wolfmqtt-src

Findings: 3
3 finding(s) posted as inline comments (see file-level comments below)

This review was generated automatically by Fenrir. Findings are non-blocking.

[Copilot]

Pull request overview

This PR addresses a broker crash caused by SIGPIPE when writing responses (e.g., PUBREC) to a socket that the peer has already closed, and adds regression coverage around the QoS 2 state-machine path involved in the reported scenario.

Changes:

• Suppress SIGPIPE in the broker POSIX network layer using MSG_NOSIGNAL (where available) and SO_NOSIGPIPE (macOS/BSD).
• Add new broker unit tests that exercise QoS 2 publish + immediate disconnect / abrupt close with an offline durable subscriber.
• Ignore newly built broker test executables in .gitignore.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 6 comments.

File	Description
src/mqtt_broker.c	Adds SIGPIPE suppression for broker socket writes (MSG_NOSIGNAL / SO_NOSIGPIPE) and installs SIGPIPE ignore in initialization paths.
tests/test_broker_connect.c	Extends mock networking to simulate read errors and adds new QoS 2 regression tests for disconnect/abrupt-close scenarios.
.gitignore	Ignores broker/unit test binaries.

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