Provided by: bpfcc-tools_0.12.0-2_all 
NAME
tcpdrop - Trace kernel-based TCP packet drops with details. Uses Linux eBPF/bcc.
SYNOPSIS
tcpdrop [-h]
DESCRIPTION
This tool traces TCP packets or segments that were dropped by the kernel, and shows details from the IP
and TCP headers, the socket state, and the kernel stack trace. This is useful for debugging cases of high
kernel drops, which can cause timer-based retransmits and performance issues.
This tool works using dynamic tracing of the tcp_drop() kernel function, which requires a recent kernel
version.
Since this uses BPF, only the root user can use this tool.
REQUIREMENTS
CONFIG_BPF and bcc.
OPTIONS
-h Print usage message. tcpdrop
FIELDS
TIME Time of the drop, in HH:MM:SS format.
PID Process ID that was on-CPU during the drop. This may be unrelated, as drops can occur on the
receive interrupt and be unrelated to the PID that was interrupted.
IP IP address family (4 or 6)
SADDR Source IP address.
SPORT Source TCP port.
DADDR Destination IP address.
DPORT Destionation TCP port.
STATE TCP session state ("ESTABLISHED", etc).
FLAGS TCP flags ("SYN", etc).
OVERHEAD
This traces the kernel tcp_drop() function, which should be low frequency, and therefore the overhead of
this tool should be negligible.
As always, test and understand this tools overhead for your types of workloads before production use.
SOURCE
This is from bcc.
https://github.com/iovisor/bcc
Also look in the bcc distribution for a companion _examples.txt file containing example usage, output,
and commentary for this tool.
OS
Linux
STABILITY
Unstable - in development.
AUTHOR
Brendan Gregg
SEE ALSO
tcplife(8), tcpaccept(8), tcpconnect(8), tcptop(8)