Hi Stephen, On Fri, Nov 21, 2008 at 2:57 PM, Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 21 Nov 2008 11:06:19 -0500 > Michael Kerrisk <mtk.manpages@xxxxxxxxxxxxxx> wrote: > >> Hello Stephen, >> >> Back in 2.6.13, you added the TCP_CONGESTION sockopt, but >> provided no man-page patch... >> >> Below is my attempt to document this sockopt. Could you please >> review. Please don't assume I've well understood the code: I >> may well have messed up in my reading of it, so review what >> I've written with care. >> >> Also, a question: was the silent truncation of the returned >> string on getsockopt() if optlen is too small really intended? >> Would it not be/have been better to error on this case? You added some other stuff below, but I got no response to the review request and the question above? >> TCP_CONGESTION (since Linux 2.6.13) >> Get or set the congestion-control algorithm for this >> socket. The optval argument is a pointer to a >> character-string buffer. >> >> For getsockopt() *optlen specifies the amount of space >> available in the buffer pointed to by optval, which >> should be at least 16 bytes (defined by the kernel- >> internal constant TCP_CA_NAME_MAX). On return, the >> buffer pointed to by optval is set to a null-terminated >> string containing the name of the congestion-control >> algorithm for this socket, and *optlen is set to the >> minimum of its original value and TCP_CA_NAME_MAX. If >> the value passed in *optlen is too small, then the >> string returned in *optval is silently truncated, and no >> terminating null byte is added. If an empty string is >> returned, then the socket is using the default conges- >> tion-control algorithm, determined as described under >> tcp_congestion_control above. >> >> For setsockopt() optlen specifies the length of the con- >> gestion-control algorithm name contained in the buffer >> pointed to by optval; this length need not include any >> terminating null byte. The algorithm "reno" is always >> permitted; other algorithms may be available, depending >> on kernel configuration. Possible errors from setsock- >> opt() include: algorithm not found/available (ENOENT); >> setting this algorithm requires the CAP_NET_ADMIN capa- >> bility (EPERM); and failure getting kernel module >> (EBUSY). > The tcp(7) man page is related (I'm a little confused by that remark: the patch at the end of my mail was *for* the tcp(7) man page; maybe you missed that.) > and seems out of date as well. Yes, many things on it are out of date. (I've made occasional requests to linux-net for help on this point, but have had little response.) > At least on this sytem (Ubuntu 8.04).it seems to be stuck back in pre 2.6.12 Yes, 2.6.12 sounds about right. > timewarp (see tcp_bic, tcp_bic_low_window, ...) values that no > longer exist. And when they disappear, no one CCs the man-page maintainer :-(. Anyway, thanks for the heads up tcp_bic* is now fixed (disappeared in 2.6.13) and tcp_westwood is now fixed (disappeared in 2.6.13) and tcp_vegas_cong_avoid is now fixed (disappeared in 2.6.13) > Should be updated as well. I'm working on it. Many updates to tcp(7) will be in man-pages-3.14. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
