ptpd logging is broken

[Joel Campbell]

On some 16.04 hosts running 2.3.1-debian1-1 we receive the following error in the ptpd.log:

2018-05-24 20:24:50.306630 ptpd2[14184].eth0 (error) (slv) Error while writing statistics (strerror: Interrupted system call)

After that error appears the ptp.log (where we log statistics) gets corrupted:

2018-05-24 20:24:47.002510, slv, 002590fffe0d0ef8(unknown)/50000cecfffe0a0a7b, 0.000326505, -0.000056357, 0.000303778, 0.000277860, -17432.175342773, P, 0.000000000, 0, 0.000000000, 0, 0, 0, 0.000277860, 0.000000000
2018-05-24 20:24:50.306607, slv, 002590fffe0d0ef8(unknown)/50000cecfffe0a0a7b, 0.000380850, -0.000061552, 0.004886770, 0.000286938, -17506.101342773, S, 0.000000000, 0, -0.000154761, 97690, -16007, 1258, 0.000286938, 0.0002018-05-24 20:24:50.306607, slv, 002590fffe0d0ef8(unknown)/50000cecfffe0a0a7b, 0.000380850, -0.000061552, 0.004886770, 0.000286938, -17506.101342773, S, 0.000000000, 0, -0.000154761, 97690, -16007, 1258, 0.000286938, 0.0002018-05-24 20:24:51.002510, slv, 002590fffe0d0ef8(unknown)/50000cecfffe0a0a7b, 0.000400021, -0.000061552,

It appears that the log stops putting line breaks in so all statistics get written to a single line from that point forward.

[Joel Campbell (joel.campbell)]

This also happens on 18.04 hosts. It makes troubleshooting PTP issues very difficult if the statistics log is not working.