dhcpcd mismatch between binary and source packages

[Stuart MacDonald]

pi@raspberrypi:~/dhcpcd $ uname -a
Linux raspberrypi 4.1.19-v7+ #858 SMP Tue Mar 15 15:56:00 GMT 2016 armv7l GNU/Linux
pi@raspberrypi:~/dhcpcd $ cat /etc/issue
Raspbian GNU/Linux 8 \n \l

dhcpcd is spamming syslog with an error:
pi@raspberrypi:~/dhcpcd $ !tail
tail -n 10 /var/log/syslog.1
Mar 20 21:34:06 raspberrypi dhcpcd[701]: usb0: dhcp if_readrawpacket: Bad file descriptor
Mar 20 21:34:06 raspberrypi dhcpcd[701]: usb0: dhcp if_readrawpacket: Bad file descriptor
Mar 20 21:34:06 raspberrypi dhcpcd[701]: usb0: dhcp if_readrawpacket: Bad file descriptor
Mar 20 21:34:06 raspberrypi dhcpcd[701]: usb0: dhcp if_readrawpacket: Bad file descriptor
Mar 20 21:34:06 raspberrypi dhcpcd[701]: usb0: dhcp if_readrawpacket: Bad file descriptor

I want to understand this better, so need to dig into the source code. I uncomment the deb-src line from /etc/apt/sources.list, sudo apt-get update, apt-get source dhcpcd. There's a mismatch:

pi@raspberrypi:~/dhcpcd $ dhcpcd --version
dhcpcd 6.7.1
Copyright (c) 2006-2015 Roy Marples
pi@raspberrypi:~/dhcpcd $ dir
total 92
drwxr-xr-x 3 pi pi 4096 Mar 24 15:35 ./
drwxr-xr-x 6 pi pi 4096 Mar 24 15:46 ../
drwxr-xr-x 4 pi pi 4096 Mar 24 15:38 dhcpcd-3.2.3/
-rw-r--r-- 1 pi pi 18696 May 4 2012 dhcpcd_3.2.3-11.diff.gz
-rw-r--r-- 1 pi pi 949 May 4 2012 dhcpcd_3.2.3-11.dsc
-rw-r--r-- 1 pi pi 53528 Apr 19 2012 dhcpcd_3.2.3.orig.tar.gz

I expected to get the source for the running binary and did not.

I've made a forum post: https://www.raspberrypi.org/forums/viewtopic.php?uid=222544&f=29&t=178450&start=0