Dropwatch is a utility to help developers and system administrators to
diagnose problems in the Linux Networking stack, specifically their
ability to diagnose where packets are getting dropped. Dropwatch aims to
improve on the following shortcomings:
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1) Consolidation, or lack thereof. Currently, to check the status of
dropped packets in the kernel, one needs to check at least 3 places, and
possibly more: The /proc/net/snmp file, the netstat utility, the tc
utility, and ethtool. Dropwatch aims to consolidate several of those
checks into one tool, making it easier for a sysadmin or developer to
detect lost packets
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2) Clarity of information. Dropped packets are not obvious. A sysadmin
needs to be intimately familiar with each of the above tools to
understand which events or statistics correlate to a dropped packet and
which do not. While that is often self evident, it is also often not.
Dropwatch aims to improve that clarity.
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3) Ambiguity. Even when a dropped packet is detected, the causes for
those dropped packets are not always clear. Does a UDPInError mean the
application receive buffer was full, or does it mean its checksum was
bad? Dropwatch attempts to disambiguate the causes for dropped packets.
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4) Performance. Utilities can be written to aggregate the data in the
various other utilities to solve some of these problems, but such
solutions require periodic polling of several interfaces, which is far
from optimal, especially when lost packets are rare. This solution
improves on the performance aspect by implementing a kernel feature which
allows asynchronous notification of dropped packets when they happen.
