ofp-group: Don't assert-fail decoding bad OF1.5 group mod type or command.

When decoding a group mod, the current code validates the group type and
command after the whole group mod has been decoded.  The OF1.5 decoder,
however, tries to use the type and command earlier, when it might still be
invalid.  This caused an assertion failure (via OVS_NOT_REACHED).  This
commit fixes the problem.

ovs-vswitchd does not enable support for OpenFlow 1.5 by default.

Reported-at: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=9249
Signed-off-by: Ben Pfaff <blp@ovn.org>
Reviewed-by: Yifeng Sun <pkusunyifeng@gmail.com>
ofputil_decode_bundle_add(const struct ofp_header *oh,
                          struct ofputil_bundle_add_msg *msg,
                          enum ofptype *typep)
{
    struct ofpbuf b = ofpbuf_const_initializer(oh, ntohs(oh->length));

    /* Pull the outer ofp_header. */
    enum ofpraw raw = ofpraw_pull_assert(&b);
    ovs_assert(raw == OFPRAW_OFPT14_BUNDLE_ADD_MESSAGE
               || raw == OFPRAW_ONFT13_BUNDLE_ADD_MESSAGE);

    /* Pull the bundle_ctrl header. */
    const struct ofp14_bundle_ctrl_msg *m = ofpbuf_pull(&b, sizeof *m);
    msg->bundle_id = ntohl(m->bundle_id);
    msg->flags = ntohs(m->flags);

    /* Pull the inner ofp_header. */
    if (b.size < sizeof(struct ofp_header)) {
        return OFPERR_OFPBFC_MSG_BAD_LEN;
    }
    msg->msg = b.data;
    if (msg->msg->version != oh->version) {
        return OFPERR_OFPBFC_BAD_VERSION;
    }
    size_t inner_len = ntohs(msg->msg->length);
    if (inner_len < sizeof(struct ofp_header) || inner_len > b.size) {
        return OFPERR_OFPBFC_MSG_BAD_LEN;
    }
    if (msg->msg->xid != oh->xid) {
        return OFPERR_OFPBFC_MSG_BAD_XID;
    }

    /* Reject unbundlable messages. */
    enum ofptype type;
    enum ofperr error = ofptype_decode(&type, msg->msg);
    if (error) {
        VLOG_WARN_RL(&bad_ofmsg_rl, "OFPT14_BUNDLE_ADD_MESSAGE contained "
                     "message is unparsable (%s)", ofperr_get_name(error));
        return OFPERR_OFPBFC_MSG_UNSUP; /* 'error' would be confusing. */
    }

    if (!ofputil_is_bundlable(type)) {
        VLOG_WARN_RL(&bad_ofmsg_rl, "%s message not allowed inside "
                     "OFPT14_BUNDLE_ADD_MESSAGE", ofptype_get_name(type));
        return OFPERR_OFPBFC_MSG_UNSUP;
    }
    if (typep) {
        *typep = type;
    }

    return 0;
}

ofputil_decode_bundle_add(const struct ofp_header *oh,
                          struct ofputil_bundle_add_msg *msg,
                          enum ofptype *typep)
{
    struct ofpbuf b = ofpbuf_const_initializer(oh, ntohs(oh->length));

    /* Pull the outer ofp_header. */
    enum ofpraw raw = ofpraw_pull_assert(&b);
    ovs_assert(raw == OFPRAW_OFPT14_BUNDLE_ADD_MESSAGE
               || raw == OFPRAW_ONFT13_BUNDLE_ADD_MESSAGE);

    /* Pull the bundle_ctrl header. */
    const struct ofp14_bundle_ctrl_msg *m = ofpbuf_pull(&b, sizeof *m);
    msg->bundle_id = ntohl(m->bundle_id);
    msg->flags = ntohs(m->flags);

    /* Pull the inner ofp_header. */
    if (b.size < sizeof(struct ofp_header)) {
        return OFPERR_OFPBFC_MSG_BAD_LEN;
    }
    msg->msg = b.data;
    if (msg->msg->version != oh->version) {
        return OFPERR_OFPBFC_BAD_VERSION;
    }
    size_t inner_len = ntohs(msg->msg->length);
    if (inner_len < sizeof(struct ofp_header) || inner_len > b.size) {
        return OFPERR_OFPBFC_MSG_BAD_LEN;
    }
    if (msg->msg->xid != oh->xid) {
        return OFPERR_OFPBFC_MSG_BAD_XID;
    }

    /* Reject unbundlable messages. */
    enum ofptype type;
    enum ofperr error = ofptype_decode(&type, msg->msg);
    if (error) {
        VLOG_WARN_RL(&bad_ofmsg_rl, "OFPT14_BUNDLE_ADD_MESSAGE contained "
                     "message is unparsable (%s)", ofperr_get_name(error));
        return OFPERR_OFPBFC_MSG_UNSUP; /* 'error' would be confusing. */
    }

    if (!ofputil_is_bundlable(type)) {
        VLOG_WARN_RL(&bad_ofmsg_rl, "%s message not allowed inside "
                     "OFPT14_BUNDLE_ADD_MESSAGE", ofptype_get_name(type));
        return OFPERR_OFPBFC_MSG_UNSUP;
    }
    if (typep) {
        *typep = type;
    }

    return 0;
}
