[pacman-dev] [PATCH 1/2] lib/dload: enforce usage of TCP keepalives

[Dan McGee]

On Sun, Jan 22, 2012 at 7:31 PM, Dave Reisner <d at falconindy.com> wrote:
> This is particularly important in the case of FTP control connections,
> which may be closed by rogue NAT/firewall devices detecting idle
> connections on larger transfers which may take 5-10+ minutes.
>
> Signed-off-by: Dave Reisner <dreisner at archlinux.org>
> ---
> This is basically on the advice of Daniel Stenberg, who mentions that it's a
> common problem that he's aware of. I have no idea if this is actually the fix
> we're looking for and I'm still unable to reproduce, but it seems plausible
> solution.
>
> Also, fuck FTP.
>
>  configure.ac        |    7 +++--
>  lib/libalpm/dload.c |   59 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 63 insertions(+), 3 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index 6941054..c8ba03f 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -174,9 +174,10 @@ AM_CONDITIONAL([HAVE_LIBGPGME], [test "x$with_gpgme" = "xyes"])
>
>  # Checks for header files.
>  AC_CHECK_HEADERS([fcntl.h float.h glob.h libintl.h limits.h locale.h \
> -                  mntent.h stddef.h string.h sys/ioctl.h sys/mount.h \
> -                  sys/param.h sys/statvfs.h sys/time.h sys/types.h \
> -                  sys/ucred.h syslog.h termios.h wchar.h])
> +                  mntent.h netinet/in.h netinet/tcp.h stddef.h string.h \
> +                  sys/ioctl.h sys/mount.h sys/param.h sys/statvfs.h \
> +                  sys/time.h sys/types.h sys/ucred.h syslog.h termios.h \
> +                  wchar.h])
>
>  # Checks for typedefs, structures, and compiler characteristics.
>  AC_C_INLINE
> diff --git a/lib/libalpm/dload.c b/lib/libalpm/dload.c
> index a3980d6..790080c 100644
> --- a/lib/libalpm/dload.c
> +++ b/lib/libalpm/dload.c
> @@ -23,11 +23,19 @@
>  #include <errno.h>
>  #include <string.h>
>  #include <unistd.h>
> +#include <sys/socket.h> /* setsockopt, SO_KEEPALIVE */
>  #include <sys/time.h>
>  #include <sys/types.h>
>  #include <sys/stat.h>
>  #include <signal.h>
>
> +#ifdef _HAVE_NETINET_IN_H
> +#include <netinet/in.h> /* IPPROTO_TCP */
> +#endif
> +#ifdef _HAVE_NETINET_TCP_H
> +#include <netinet/tcp.h> /* TCP_KEEPINTVL, TCP_KEEPIDLE */
> +#endif
> +
>  #ifdef HAVE_LIBCURL
>  #include <curl/curl.h>
>  #endif
> @@ -215,6 +223,53 @@ static size_t parse_headers(void *ptr, size_t size, size_t nmemb, void *user)
>        return realsize;
>  }
>
> +static int curl_sockopt_cb(void *userdata, curl_socket_t curlfd,
> +               curlsocktype purpose)
> +{
> +       alpm_handle_t *handle = userdata;
> +
> +       int onoff = 1;
> +
> +#ifdef TCP_KEEPIDLE
> +       int keepidle = TCP_KEEPIDLE;
> +#endif
> +#ifdef TCP_KEEPINTVL
> +       int keepintvl = TCP_KEEPINTVL;
> +#endif
> +
> +       switch(purpose) {
> +               case CURLSOCKTYPE_IPCXN:
> +                       if(setsockopt(curlfd, SOL_SOCKET, SO_KEEPALIVE, (void *)&onoff,
> +                                                                               sizeof(onoff)) < 0) {
> +                               /* don't abort operation, just log to debug */
> +                               _alpm_log(handle, ALPM_LOG_DEBUG, "Failed to set SO_KEEPALIVE on fd %d\n",
> +                                               curlfd);
This makes sense...

> +                       }
> +                       else {
> +#ifdef TCP_KEEPIDLE
> +                               if(setsockopt(curlfd, IPPROTO_TCP, TCP_KEEPIDLE, (void *)&keepidle,
> +                                                                                       sizeof(keepidle)) < 0) {
> +                                       /* don't abort operation, just log to debug */
> +                                       _alpm_log(handle, ALPM_LOG_DEBUG, "Failed to set TCP_KEEPIDLE on fd %d\n",
> +                                                       curlfd);
> +                               }
> +#endif
> +#ifdef TCP_KEEPINTVL
> +                               if(setsockopt(curlfd, IPPROTO_TCP, TCP_KEEPINTVL, (void *)&keepintvl,
> +                                                                                       sizeof(keepintvl)) < 0) {
> +                                       /* don't abort operation, just log to debug */
> +                                       _alpm_log(handle, ALPM_LOG_DEBUG, "Failed to set TCP_KEEPINTVL on fd %d\n",
> +                                                       curlfd);
> +                               }
> +#endif
These, however, seem a bit suspect.

1) Linux-specific (although you guarded it fine, this is quite ugly).
2) Looks like the default keepidle value is 7200 secs; aka 2 hours.
This is far too long, but do we need to be messing with keepintvl?
That defaults to 75 seconds which seems relatively sane.
3) Why are you using TCP_KEEPIDLE and TCP_KEEPINTVL for both the
option_name AND option_value? Passing a logical value rather than the
arbitrary constant values (4 and 5) would seem to make more sense in
any case. Probably something like 60 seconds for both would work.

> +                       }
> +               default:
> +                       break;
> +       }
> +
> +       return 0;
> +}
> +
>  static void curl_set_handle_opts(struct dload_payload *payload,
>                CURL *curl, char *error_buffer)
>  {
> @@ -239,6 +294,8 @@ static void curl_set_handle_opts(struct dload_payload *payload,
>        curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, parse_headers);
>        curl_easy_setopt(curl, CURLOPT_WRITEHEADER, (void *)payload);
>        curl_easy_setopt(curl, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
> +       curl_easy_setopt(curl, CURLOPT_SOCKOPTFUNCTION, curl_sockopt_cb);
> +       curl_easy_setopt(curl, CURLOPT_SOCKOPTDATA, (void *)handle);
>
>        _alpm_log(handle, ALPM_LOG_DEBUG, "url: %s\n", payload->fileurl);
>
> @@ -388,6 +445,8 @@ static int curl_download_internal(struct dload_payload *payload,
>
>        /* perform transfer */
>        payload->curlerr = curl_easy_perform(curl);
> +       _alpm_log(handle, ALPM_LOG_DEBUG, "curl returned error %d from transfer\n",
> +                       payload->curlerr);
>
>        /* disconnect relationships from the curl handle for things that might go out
>         * of scope, but could still be touched on connection teardown.  This really
> --
> 1.7.8.4
>
>