> On Aug 6, 2018, at 1:49 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: > > > >> On Aug 6, 2018, at 12:06 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >> >> On Mon, Aug 6, 2018 at 10:46 AM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote: >>> >>> >>>> On Aug 2, 2018, at 12:42 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >>>> >>>> On Thu, Aug 2, 2018 at 11:14 AM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >>>>> Hi folks, >>>>> >>>>> There is no documentation of this behavior but when "noresvport" is >>>>> specified, the client will not try to re-use the port upon connection >>>>> re-establishement. Is this an oversight or a desired behavior (ie., >>>>> client doesn't need to be conservative and re-use ports)? >>>>> >>>>> Thank you. >>>> >>>> I'm going to speculate on the reason myself and would like to hear >>>> some folks thoughts. >>>> >>>> When we specify "noresvport" we use port=0 value that tells the kernel >>>> - use any port. When connection is re-established port=0 so NFS has no >>>> control over which port the kernel will choose. >>>> >>>> When client re-establishes the connection with a different port, that >>>> has an effect on the server's replay cache. Any thoughts on that? >>>> >>>> Should the client remember which non-privileged port it used and then >>>> the next time request a specific port? >>> >>> The basic constraint is that: >>> >>> If the client actively disconnects, or if the client is using an NFSv4 >>> session, then for a fresh connection the client is free to use any >>> available source port in the range selected by the "resvport" mount >>> option. >>> >>> If there is no NFSv4 session and the server or the network transport >>> actively disconnects (say, due to a keep-alive timeout), the client >>> should attempt to use the same source port as the previous connection >>> in order to preserve DRC content on the server. >> >> Hi Chuck, >> >> Thanks for the reply. I'm considering your 2nd case where the server >> reset the connection and client is re-establishing it and this is a v3 >> mount (this DRC is important). When "noresvport" is specified, then >> the kernel makes no attempts at re-use the same non-reserved port. >> However, I'm not sure it is possible to re-use a non-reserved port. > > Why do you believe that? That was terse. What I mean is, I don't know whether it is possible or not to re-use an ephemeral port. I don't know of a reason why it would not be possible to re-use one. Do you? >> Given this behavior, shouldn't we be discouraging folks to mount with >> v3 and "noresvport" option? -- Chuck Lever -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
