Changelog and backwards compat notes for VXLAN support #1334
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afshin-paydar
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Sep 24, 2025
When attempting to open a non-existent network interface on Linux, libpcap would return PCAP_ERROR_PERM_DENIED instead of the correct PCAP_ERROR_NO_SUCH_DEVICE. This occurred because the privileged socket(PF_PACKET, SOCK_RAW, 0) call in setup_socket() would fail with permission errors before interface validation could occur. This fix adds an interface existence check using an unprivileged AF_INET socket and SIOCGIFINDEX ioctl before attempting to create the privileged packet socket. Non-existent interfaces now correctly return PCAP_ERROR_NO_SUCH_DEVICE. This resolves the issue where applications like tcpdump would report "Permission denied" instead of "No such device exists" for non-existent interfaces, breaking their fallback logic from interface names to indices. Note: BSD/macOS platforms have the same underlying issue where BPF device access fails with permission errors before interface validation. This should be addressed in a separate commit. Fixes: libpcap issue the-tcpdump-group#1538 Related: tcpdump issue the-tcpdump-group#1334 Signed-off-by: Afshin Paydar <afshin.paydar@deriv.com>
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Following up #1273, this change adds a backwards compatibility note to the
pcap-filtermanual page for thevxlankeyword, and adds an entry to the changelog for this feature.