[ovs-dev] [PATCH v4 2/2 ovn] Add support for DHCP domain search option (119)

Numan Siddique numans at ovn.org
Mon Jun 8 14:52:07 UTC 2020


On Mon, Jun 1, 2020 at 11:45 PM Ankur Sharma <svc.mail.git at nutanix.com>
wrote:

> From: Dhathri Purohith <dhathri.purohith at nutanix.com>
>
> Domain search list is encoded according to the specifications in RFC 1035,
> section 4.1.4.
>
> Signed-off-by: Dhathri Purohith <dhathri.purohith at nutanix.com>
> Signed-off-by: Ankur Sharma <ankur.sharma at nutanix.com>
>

Hi Dhathri,

Thanks for the patch. Please see below for a few comments.

Thanks
Numan


> ---
>  lib/actions.c       | 100
> +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  lib/ovn-l7.h        |   3 ++
>  northd/ovn-northd.c |   1 +
>  ovn-sb.ovsschema    |   6 ++--
>  ovn-sb.xml          |  11 ++++++
>  tests/ovn.at        |   3 ++
>  tests/test-ovn.c    |   1 +
>  7 files changed, 121 insertions(+), 4 deletions(-)
>
> diff --git a/lib/actions.c b/lib/actions.c
> index f21be6d..8f5ed61 100644
> --- a/lib/actions.c
> +++ b/lib/actions.c
> @@ -1982,7 +1982,8 @@ parse_gen_opt(struct action_context *ctx, struct
> ovnact_gen_option *o,
>          return;
>      }
>
> -    if (!strcmp(o->option->type, "str")) {
> +    if (!strcmp(o->option->type, "str") ||
> +        !strcmp(o->option->type, "domains")) {
>          if (o->value.type != EXPR_C_STRING) {
>              lexer_error(ctx->lexer, "%s option %s requires string value.",
>                          opts_type, o->option->name);
> @@ -2317,6 +2318,103 @@ encode_put_dhcpv4_option(const struct
> ovnact_gen_option *o,
>             opt_header[1] = sizeof(ovs_be32);
>             ofpbuf_put(ofpacts, &c->value.ipv4, sizeof(ovs_be32));
>          }
> +    } else if (!strcmp(o->option->type, "domains")) {
> +        /* Please refer to RFC 1035, section 4.1.4 for the format of
> encoding
> +         * domain names. Below is an example for encoding a search list
> +         * consisting of the "abc.com" and "xyz.abc.com".
> +         *
> +         *
> +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +         * |119|14 | 3 |'a'|'b'|'c'| 3 |'c'|'o'|'m'| 0
> |'x'|'y'|'z'|xC0|x00|
> +         *
> +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
> +         *
> +         * The encoding of "abc.com" ends with 0 to mark the end of the
> +         * domain name as required by RFC 1035.
> +         *
> +         * The encoding of "xyz" (for "xyz.abc.com") ends with the
> two-octet
> +         * compression pointer C000 (hex), which points to offset 0 where
> +         * another validly encoded domain name can be found to complete
> +         * the name ("abc.com").
> +         */
> +        typedef struct namemap_node {
> +            struct hmap_node node;
> +            uint16_t offset;
> +            char *name;
> +        } namemap_node;
>

in OVN/OVS generally a struct is not typedef'ed. Please see
https://docs.ovn.org/en/latest/internals/contributing/coding-style.html
I'd suggest to removethe typedef.


> +        struct hmap namemap;
> +        hmap_init(&namemap);
> +        namemap_node *ref;
>


> +        /* Encoding adds 2 bytes (one for length and one for delimiter)
> for
> +         * every domain name that is unique. If all the domain names are
> unique
> +         * (which probably never happens in real world), then encoded
> string
> +         * could be longer than the original string. Just to be on the
> safer
> +         * side, allocate the (approx.) worst case length here.
> +         */
> +        uint8_t *dns_encoded = xzalloc(2 * strlen(c->string));
> +        uint8_t encode_offset = 0;
> +        char *domain_list = xstrdup(c->string), *dom_ptr = NULL;
> +        for (char *domain = strtok_r(domain_list, ",", &dom_ptr);
> +             domain != NULL;
> +             domain = strtok_r(NULL, ",", &dom_ptr)) {
> +            if (strlen(domain) > DOMAIN_NAME_MAX_LEN) {
> +                VLOG_WARN("Domain names longer than 255 characters are
> not"
> +                          "supported");
> +                goto out;
> +            }
> +            char *label_ptr = NULL, *label;
> +            for (label = strtok_r(domain, ".", &label_ptr);
> +                 label != NULL;
> +                 label = strtok_r(NULL, ".", &label_ptr)) {
> +                ref = NULL;
> +                /* Check if we have already encoded this label and
> +                 * fill in the reference, if yes. */
> +                uint32_t label_hash = hash_string(label, 0);
> +                HMAP_FOR_EACH_IN_BUCKET (ref, node, label_hash, &namemap)
> {
>

I think for this usecase, we can use shash and make sure that a label is
added only once to
the shash (shash_add_once()). It will be easier to search for the label.


> +                    if (!strcmp(label, ref->name)) {
> +                        ovs_be16 temp = htons(0xc000) |
> htons(ref->offset);
> +                        memcpy(dns_encoded + encode_offset, &temp,
> +                               sizeof(temp));
> +                        encode_offset += sizeof(temp);
> +                        break;
> +                    }
> +                }
> +                /* Break, since we have already filled the offset for this
> +                 * domain. */
> +                if (ref != NULL) {
> +                    break;
> +                } else {
> +                    /* The label was not encoded before, encode it now
> and add
> +                     * the offset to the namemap map. */
> +                    ref = xzalloc(sizeof *ref);
> +                    ref->name = xstrdup(label);
> +                    ref->offset = encode_offset;
> +                    hmap_insert(&namemap, &ref->node, label_hash);
> +
> +                    uint8_t len = strlen(label);
> +                    memcpy(dns_encoded + encode_offset, &len,
> sizeof(uint8_t));
> +                    encode_offset += sizeof(uint8_t);
> +                    memcpy(dns_encoded + encode_offset, label, len);
> +                    encode_offset += len;
> +                }
> +            }
> +            /* Add the end marker (0 byte) to determine the end of the
> +             * domain. */
> +            if (label == NULL) {
> +                uint8_t end = 0;
> +                memcpy(dns_encoded + encode_offset, &end,
> sizeof(uint8_t));
> +                encode_offset += sizeof(uint8_t);
> +            }
> +        }
> +        opt_header[1] = encode_offset;
> +        ofpbuf_put(ofpacts, dns_encoded, encode_offset);
> +
> +        out:
> +            HMAP_FOR_EACH_POP (ref, node, &namemap) {
> +                free(ref->name);
> +                free(ref);
> +            }
> +            hmap_destroy(&namemap);
> +            free(domain_list);
> +            free(dns_encoded);
>      }
>  }
>
> diff --git a/lib/ovn-l7.h b/lib/ovn-l7.h
> index 38555db..f34bc0d 100644
> --- a/lib/ovn-l7.h
> +++ b/lib/ovn-l7.h
> @@ -34,6 +34,7 @@ struct gen_opts_map {
>      size_t code;
>  };
>
> +#define DOMAIN_NAME_MAX_LEN 255
>  #define DHCP_BROADCAST_FLAG 0x8000
>
>  #define DHCP_OPTION(NAME, CODE, TYPE) \
> @@ -81,6 +82,8 @@ struct gen_opts_map {
>  #define DHCP_OPT_PATH_PREFIX DHCP_OPTION("path_prefix", 210, "str")
>  #define DHCP_OPT_TFTP_SERVER_ADDRESS \
>      DHCP_OPTION("tftp_server_address", 150, "ipv4")
> +#define DHCP_OPT_DOMAIN_SEARCH_LIST \
> +    DHCP_OPTION("domain_search_list", 119, "domains")
>
>  #define DHCP_OPT_ARP_CACHE_TIMEOUT \
>      DHCP_OPTION("arp_cache_timeout", 35, "uint32")
> diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
> index ef08414..4ec2034 100644
> --- a/northd/ovn-northd.c
> +++ b/northd/ovn-northd.c
> @@ -11336,6 +11336,7 @@ static struct gen_opts_map supported_dhcp_opts[] =
> {
>      DHCP_OPT_DOMAIN_NAME,
>      DHCP_OPT_ARP_CACHE_TIMEOUT,
>      DHCP_OPT_TCP_KEEPALIVE_INTERVAL,
> +    DHCP_OPT_DOMAIN_SEARCH_LIST,
>  };
>
>  static struct gen_opts_map supported_dhcpv6_opts[] = {
> diff --git a/ovn-sb.ovsschema b/ovn-sb.ovsschema
> index 2ec729b..99c5de8 100644
> --- a/ovn-sb.ovsschema
> +++ b/ovn-sb.ovsschema
> @@ -1,7 +1,7 @@
>  {
>      "name": "OVN_Southbound",
> -    "version": "2.8.1",
> -    "cksum": "236203406 21905",
> +    "version": "2.8.2",
> +    "cksum": "464326363 21916",
>      "tables": {
>          "SB_Global": {
>              "columns": {
> @@ -218,7 +218,7 @@
>                          "type": "string",
>                          "enum": ["set", ["bool", "uint8", "uint16",
> "uint32",
>                                           "ipv4", "static_routes", "str",
> -                                         "host_id"]]}}}},
> +                                         "host_id", "domains"]]}}}},
>              "isRoot": true},
>          "DHCPv6_Options": {
>              "columns": {
> diff --git a/ovn-sb.xml b/ovn-sb.xml
> index 208fb93..a6da80b 100644
> --- a/ovn-sb.xml
> +++ b/ovn-sb.xml
> @@ -3232,6 +3232,17 @@ tcp.flags = RST;
>            </p>
>          </dd>
>
> +        <dt><code>value: domains</code></dt>
> +        <dd>
> +          <p>
> +            This indicates that the value of the DHCP option is a domain
> name
> +            or a comma separated list of domain names.
> +          </p>
> +
> +          <p>
> +            Example. "name=domain_search_list", "code=119",
> "type=domains".
> +          </p>
>

You also need to update the ovn-nb.xml documentation.


> +        </dd>
>        </dl>
>      </column>
>    </table>
> diff --git a/tests/ovn.at b/tests/ovn.at
> index fa2592c..91ec564 100644
> --- a/tests/ovn.at
> +++ b/tests/ovn.at
> @@ -1218,6 +1218,9 @@ reg0[15] =
> put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.255.0,
>  reg0[15] =
> put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.255.0,mtu=1400,ip_forward_enable=1,default_ttl=121,dns_server={8.8.8.8,7.7.7.7},classless_static_route={
> 30.0.0.0/24,10.0.0.4,40.0.0.0/16,10.0.0.6,0.0.0.0/0,10.0.0.1
> },ethernet_encap=1,router_discovery=0,tftp_server="tftp_server_test");
>      formats as reg0[15] = put_dhcp_opts(offerip = 10.0.0.4, router =
> 10.0.0.1, netmask = 255.255.255.0, mtu = 1400, ip_forward_enable = 1,
> default_ttl = 121, dns_server = {8.8.8.8, 7.7.7.7}, classless_static_route
> = {30.0.0.0/24, 10.0.0.4, 40.0.0.0/16, 10.0.0.6, 0.0.0.0/0, 10.0.0.1},
> ethernet_encap = 1, router_discovery = 0, tftp_server = "tftp_server_test");
>      encodes as
> controller(userdata=00.00.00.02.00.00.00.00.00.01.de.10.00.00.00.6f.0a.00.00.04.03.04.0a.00.00.01.01.04.ff.ff.ff.00.1a.02.05.78.13.01.01.17.01.79.06.08.08.08.08.08.07.07.07.07.79.14.18.1e.00.00.0a.00.00.04.10.28.00.0a.00.00.06.00.0a.00.00.01.24.01.01.1f.01.00.42.10.74.66.74.70.5f.73.65.72.76.65.72.5f.74.65.73.74,pause)
> +reg2[5] =
> put_dhcp_opts(offerip=10.0.0.4,router=10.0.0.1,netmask=255.255.254.0,mtu=1400,domain_name="
> ovn.org",wpad="https://example.org",bootfile_name="
> https://127.0.0.1/boot.ipxe",path_prefix="/tftpboot",domain_search_list="
> ovn.org,abc.ovn.org");
> +    formats as reg2[5] = put_dhcp_opts(offerip = 10.0.0.4, router =
> 10.0.0.1, netmask = 255.255.254.0, mtu = 1400, domain_name = "ovn.org",
> wpad = "https://example.org", bootfile_name = "https://127.0.0.1/boot.ipxe",
> path_prefix = "/tftpboot", domain_search_list = "ovn.org,abc.ovn.org");
> +    encodes as
> controller(userdata=00.00.00.02.00.00.00.00.00.01.de.10.00.00.00.25.0a.00.00.04.03.04.0a.00.00.01.01.04.ff.ff.fe.00.1a.02.05.78.0f.07.6f.76.6e.2e.6f.72.67.fc.13.68.74.74.70.73.3a.2f.2f.65.78.61.6d.70.6c.65.2e.6f.72.67.43.1b.68.74.74.70.73.3a.2f.2f.31.32.37.2e.30.2e.30.2e.31.2f.62.6f.6f.74.2e.69.70.78.65.d2.09.2f.74.66.74.70.62.6f.6f.74.77.0f.03.6f.76.6e.03.6f.72.67.00.03.61.62.63.c0.00,pause)
>

It will be good to add negative cases of encoding here.

And also enhance the test_dhcp test case.

Thanks
Numan


>
>  reg1[0..1] = put_dhcp_opts(offerip = 1.2.3.4, router = 10.0.0.1);
>      Cannot use 2-bit field reg1[0..1] where 1-bit field is required.
> diff --git a/tests/test-ovn.c b/tests/test-ovn.c
> index 4391694..b43f67f 100644
> --- a/tests/test-ovn.c
> +++ b/tests/test-ovn.c
> @@ -189,6 +189,7 @@ create_gen_opts(struct hmap *dhcp_opts, struct hmap
> *dhcpv6_opts,
>      dhcp_opt_add(dhcp_opts, "tftp_server_address", 150, "ipv4");
>      dhcp_opt_add(dhcp_opts, "arp_cache_timeout", 35, "uint32");
>      dhcp_opt_add(dhcp_opts, "tcp_keepalive_interval", 38, "uint32");
> +    dhcp_opt_add(dhcp_opts, "domain_search_list", 119, "domains");
>
>      /* DHCPv6 options. */
>      hmap_init(dhcpv6_opts);
> --
> 1.8.3.1
>
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