[systemd-devel] [PATCH] networkd: send hostname to dhcp server

[Tom Gundersen]

On Tue, Jul 1, 2014 at 1:52 AM, Eugene Yakubovich
<eugene.yakubovich at coreos.com> wrote:
> Send hostname (option 12) in DISCOVER and REQUEST messages so the
> DHCP server could use it to register with dynamic DNS and such.

Nice!

A couple of minor nits below. Apart from that, could you add a config
option to make this opt-out (I'm sure people will request to be able
not to leak this information), and also add an entry to the manpage
about it?

> ---
>  src/libsystemd-network/sd-dhcp-client.c | 35 +++++++++++++++++++++++++++++++++
>  src/network/networkd-link.c             | 26 ++++++++++++++++++++++++
>  src/systemd/sd-dhcp-client.h            |  1 +
>  3 files changed, 62 insertions(+)
>
> diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
> index 1603c41..44a5e8a 100644
> --- a/src/libsystemd-network/sd-dhcp-client.c
> +++ b/src/libsystemd-network/sd-dhcp-client.c
> @@ -56,6 +56,7 @@ struct sd_dhcp_client {
>                  uint8_t type;
>                  struct ether_addr mac_addr;
>          } _packed_ client_id;
> +        char *hostname;
>          uint32_t xid;
>          usec_t start_time;
>          uint16_t secs;
> @@ -178,6 +179,20 @@ int sd_dhcp_client_set_mac(sd_dhcp_client *client,
>          return 0;
>  }
>
> +int sd_dhcp_client_set_hostname(sd_dhcp_client *client,
> +                        const char *hostname) {
> +
> +        assert_return(client, -EINVAL);
> +        assert_return(hostname, -EINVAL);
> +
> +        if (client->hostname && streq(client->hostname, hostname) )

Hm, streq_ptr()?

> +                return 0;
> +
> +        client->hostname = strdup(hostname);

Better free the old hostname to avoid a leak.

> +        return 0;
> +}
> +
>  int sd_dhcp_client_get_lease(sd_dhcp_client *client, sd_dhcp_lease **ret) {
>          assert_return(client, -EINVAL);
>          assert_return(ret, -EINVAL);
> @@ -386,6 +401,17 @@ static int client_send_discover(sd_dhcp_client *client) {
>                          return r;
>          }
>
> +        /* it is unclear from RFC 2131 if client should send hostname in
> +           DHCPDISCOVER but dhclient does and so we do as well
> +        */
> +        if (client->hostname) {
> +                r = dhcp_option_append(&discover->dhcp, optlen, &optoffset, 0,
> +                                       DHCP_OPTION_HOST_NAME,
> +                                       strlen(client->hostname), client->hostname);
> +                if (r < 0)
> +                        return r;
> +        }
> +
>          r = dhcp_option_append(&discover->dhcp, optlen, &optoffset, 0,
>                                 DHCP_OPTION_END, 0, NULL);
>          if (r < 0)
> @@ -477,6 +503,14 @@ static int client_send_request(sd_dhcp_client *client) {
>                  return -EINVAL;
>          }
>
> +        if (client->hostname) {
> +                r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
> +                                       DHCP_OPTION_HOST_NAME,
> +                                       strlen(client->hostname), client->hostname);
> +                if (r < 0)
> +                        return r;
> +        }
> +
>          r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
>                                 DHCP_OPTION_END, 0, NULL);
>          if (r < 0)
> @@ -1363,6 +1397,7 @@ sd_dhcp_client *sd_dhcp_client_unref(sd_dhcp_client *client) {
>                  sd_dhcp_lease_unref(client->lease);
>
>                  free(client->req_opts);
> +                free(client->hostname);
>                  free(client);
>          }
>
> diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
> index 9296a59..9d849a0 100644
> --- a/src/network/networkd-link.c
> +++ b/src/network/networkd-link.c
> @@ -21,6 +21,7 @@
>
>  #include <netinet/ether.h>
>  #include <linux/if.h>
> +#include <unistd.h>
>
>  #include "networkd.h"
>  #include "libudev-private.h"
> @@ -1846,6 +1847,19 @@ static int link_enter_enslave(Link *link) {
>          return 0;
>  }
>
> +/* make sure the hostname is not "localhost" */
> +static bool is_localhost(const char *hostname) {
> +        char *hostend;
> +
> +        assert(hostname);
> +
> +        hostend = strchr(hostname, '.');
> +        if (hostend)
> +                return strneq(hostname, "localhost", (hostend - hostname));
> +        else
> +                return streq(hostname, "localhost");
> +}
> +
>  static int link_configure(Link *link) {
>          int r;
>
> @@ -1886,6 +1900,8 @@ static int link_configure(Link *link) {
>          }
>
>          if (link->network->dhcp) {
> +                char hostname[HOST_NAME_MAX];
> +
>                  r = sd_dhcp_client_new(&link->dhcp_client);
>                  if (r < 0)
>                          return r;
> @@ -1911,6 +1927,16 @@ static int link_configure(Link *link) {
>                          if (r < 0)
>                                  return r;
>                  }
> +
> +                r = gethostname(hostname, sizeof(hostname));
> +                if (r < 0)
> +                        return r;
> +
> +                if (!is_localhost(hostname)) {
> +                        r = sd_dhcp_client_set_hostname(link->dhcp_client, hostname);
> +                        if (r < 0)
> +                                return r;
> +                }
>          }
>
>          if (link->network->dhcp_server) {
> diff --git a/src/systemd/sd-dhcp-client.h b/src/systemd/sd-dhcp-client.h
> index 5818ec4..7b5b938 100644
> --- a/src/systemd/sd-dhcp-client.h
> +++ b/src/systemd/sd-dhcp-client.h
> @@ -50,6 +50,7 @@ int sd_dhcp_client_set_request_address(sd_dhcp_client *client,
>  int sd_dhcp_client_set_index(sd_dhcp_client *client, int interface_index);
>  int sd_dhcp_client_set_mac(sd_dhcp_client *client,
>                             const struct ether_addr *addr);
> +int sd_dhcp_client_set_hostname(sd_dhcp_client *client, const char *hostname);
>  int sd_dhcp_client_get_lease(sd_dhcp_client *client, sd_dhcp_lease **ret);
>
>  int sd_dhcp_client_stop(sd_dhcp_client *client);
> --
> 1.9.1
>
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