[PATCH 2/2] udhcpc: fixed a TODO in fill_envp using option scanner

Denys Vlasenko vda.linux at googlemail.com
Mon Jun 29 13:40:43 UTC 2020


Applied, thanks!!!!

On Tue, Jun 23, 2020 at 3:41 PM Martin Lewis <martin.lewis.x84 at gmail.com> wrote:
>
> fill_envp now iterates over the packet only once instead of a few hundred times
> using the new option scanner.
>
> Signed-off-by: Martin Lewis <martin.lewis.x84 at gmail.com>
> ---
>  networking/udhcp/dhcpc.c | 201 ++++++++++++++++++++---------------------------
>  1 file changed, 87 insertions(+), 114 deletions(-)
>
> diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
> index 102178a4f..2669428e1 100644
> --- a/networking/udhcp/dhcpc.c
> +++ b/networking/udhcp/dhcpc.c
> @@ -386,59 +386,81 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
>         return ret;
>  }
>
> +static void putenvp(llist_t **envp, char *new_opt)
> +{
> +       putenv(new_opt);
> +       llist_add_to(envp, new_opt);
> +}
> +
> +static int is_unknown_opt(uint8_t code, const struct dhcp_optflag **dh, const char **opt_name)
> +{
> +    *opt_name = "";
> +
> +    /* Find the option:
> +     * dhcp_optflags is sorted so we stop searching when dh->code >= code, which is faster
> +     * than iterating over the entire array.
> +     * Options which don't have a match in dhcp_option_strings[], e.g DHCP_REQUESTED_IP,
> +     * are located after the sorted array, so these entries will never be reached
> +     * and they'll count as unknown options.
> +     */
> +    for (*dh = dhcp_optflags; (*dh)->code && (*dh)->code < code; (*dh)++);
> +
> +    if ((*dh)->code == code)
> +        *opt_name = nth_string(dhcp_option_strings, (*dh - dhcp_optflags));
> +
> +    return (*dh)->code > code;
> +}
> +
>  /* put all the parameters into the environment */
> -static char **fill_envp(struct dhcp_packet *packet)
> +static llist_t *fill_envp(struct dhcp_packet *packet)
>  {
> -       int envc;
> -       int i;
> -       char **envp, **curr;
> -       const char *opt_name;
> -       uint8_t *temp;
> -       uint8_t overload = 0;
> -
> -#define BITMAP unsigned
> -#define BBITS (sizeof(BITMAP) * 8)
> -#define BMASK(i) (1 << (i & (sizeof(BITMAP) * 8 - 1)))
> -#define FOUND_OPTS(i) (found_opts[(unsigned)i / BBITS])
> -       BITMAP found_opts[256 / BBITS];
> -
> -       memset(found_opts, 0, sizeof(found_opts));
> -
> -       /* We need 7 elements for:
> -        * "interface=IFACE"
> -        * "ip=N.N.N.N" from packet->yiaddr
> -        * "giaddr=IP" from packet->gateway_nip (unless 0)
> -        * "siaddr=IP" from packet->siaddr_nip (unless 0)
> -        * "boot_file=FILE" from packet->file (unless overloaded)
> -        * "sname=SERVER_HOSTNAME" from packet->sname (unless overloaded)
> -        * terminating NULL
> -        */
> -       envc = 7;
> -       /* +1 element for each option, +2 for subnet option: */
> -       if (packet) {
> -               /* note: do not search for "pad" (0) and "end" (255) options */
> -//TODO: change logic to scan packet _once_
> -               for (i = 1; i < 255; i++) {
> -                       temp = udhcp_get_option(packet, i);
> -                       if (temp) {
> -                               if (i == DHCP_OPTION_OVERLOAD)
> -                                       overload |= *temp;
> -                               else if (i == DHCP_SUBNET)
> -                                       envc++; /* for $mask */
> -                               envc++;
> -                               /*if (i != DHCP_MESSAGE_TYPE)*/
> -                               FOUND_OPTS(i) |= BMASK(i);
> -                       }
> -               }
> -       }
> -       curr = envp = xzalloc(sizeof(envp[0]) * envc);
> +       char *new_opt;
> +       uint8_t *optptr;
> +       const struct dhcp_optflag *dh;
> +       struct dhcp_scan_state scan_state;
> +       const char *opt_name = "";
> +       llist_t *envp = NULL;
>
> -       *curr = xasprintf("interface=%s", client_data.interface);
> -       putenv(*curr++);
> +       new_opt = xasprintf("interface=%s", client_data.interface);
> +       putenvp(&envp, new_opt);
>
>         if (!packet)
>                 return envp;
>
> +       init_scan_state(packet, &scan_state);
> +
> +    /* Iterate over the packet options.
> +     * Handle each option based on whether it's an unknown / known option.
> +     * There may be (although unlikely) duplicate options. For now, only the last
> +     * appearing option will be stored in the environment, and all duplicates
> +     * are freed properly.
> +     * Long options may be implemented in the future (see RFC 3396) if needed.
> +     */
> +       while ((optptr = udhcp_scan_options(packet, &scan_state)) != NULL) {
> +               uint8_t code = optptr[OPT_CODE];
> +               uint8_t len = optptr[OPT_LEN];
> +               uint8_t *data = optptr + OPT_DATA;
> +
> +               if (is_unknown_opt(code, &dh, &opt_name)) {
> +                       unsigned ofs;
> +
> +                       new_opt = xmalloc(sizeof("optNNN=") + 1 + len*2);
> +                       ofs = sprintf(new_opt, "opt%u=", code);
> +                       *bin2hex(new_opt + ofs, (char *)data, len) = '\0';
> +                       putenvp(&envp, new_opt);
> +               } else {
> +                       new_opt = xmalloc_optname_optval(data, dh, opt_name);
> +                       putenvp(&envp, new_opt);
> +
> +                       if (code == DHCP_SUBNET && len == 4) {
> +                               uint32_t subnet;
> +                               move_from_unaligned32(subnet, data);
> +                               new_opt = xasprintf("mask=%u", mton(subnet));
> +                               putenvp(&envp, new_opt);
> +                       }
> +               }
> +       }
> +
>         /* Export BOOTP fields. Fields we don't (yet?) export:
>          * uint8_t op;      // always BOOTREPLY
>          * uint8_t htype;   // hardware address type. 1 = 10mb ethernet
> @@ -452,77 +474,31 @@ static char **fill_envp(struct dhcp_packet *packet)
>          * uint8_t chaddr[16]; // link-layer client hardware address (MAC)
>          */
>         /* Most important one: yiaddr as $ip */
> -       *curr = xmalloc(sizeof("ip=255.255.255.255"));
> -       sprint_nip(*curr, "ip=", (uint8_t *) &packet->yiaddr);
> -       putenv(*curr++);
> +       new_opt = xmalloc(sizeof("ip=255.255.255.255"));
> +       sprint_nip(new_opt, "ip=", (uint8_t *) &packet->yiaddr);
> +       putenvp(&envp, new_opt);
> +
>         if (packet->siaddr_nip) {
>                 /* IP address of next server to use in bootstrap */
> -               *curr = xmalloc(sizeof("siaddr=255.255.255.255"));
> -               sprint_nip(*curr, "siaddr=", (uint8_t *) &packet->siaddr_nip);
> -               putenv(*curr++);
> +               new_opt = xmalloc(sizeof("siaddr=255.255.255.255"));
> +               sprint_nip(new_opt, "siaddr=", (uint8_t *) &packet->siaddr_nip);
> +               putenvp(&envp, new_opt);
>         }
>         if (packet->gateway_nip) {
>                 /* IP address of DHCP relay agent */
> -               *curr = xmalloc(sizeof("giaddr=255.255.255.255"));
> -               sprint_nip(*curr, "giaddr=", (uint8_t *) &packet->gateway_nip);
> -               putenv(*curr++);
> +               new_opt = xmalloc(sizeof("giaddr=255.255.255.255"));
> +               sprint_nip(new_opt, "giaddr=", (uint8_t *) &packet->gateway_nip);
> +               putenvp(&envp, new_opt);
>         }
> -       if (!(overload & FILE_FIELD) && packet->file[0]) {
> +       if (!(scan_state.overload & FILE_FIELD) && packet->file[0]) {
>                 /* watch out for invalid packets */
> -               *curr = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
> -               putenv(*curr++);
> +               new_opt = xasprintf("boot_file=%."DHCP_PKT_FILE_LEN_STR"s", packet->file);
> +               putenvp(&envp, new_opt);
>         }
> -       if (!(overload & SNAME_FIELD) && packet->sname[0]) {
> +       if (!(scan_state.overload & SNAME_FIELD) && packet->sname[0]) {
>                 /* watch out for invalid packets */
> -               *curr = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
> -               putenv(*curr++);
> -       }
> -
> -       /* Export known DHCP options */
> -       opt_name = dhcp_option_strings;
> -       i = 0;
> -       while (*opt_name) {
> -               uint8_t code = dhcp_optflags[i].code;
> -               BITMAP *found_ptr = &FOUND_OPTS(code);
> -               BITMAP found_mask = BMASK(code);
> -               if (!(*found_ptr & found_mask))
> -                       goto next;
> -               *found_ptr &= ~found_mask; /* leave only unknown options */
> -               temp = udhcp_get_option(packet, code);
> -               *curr = xmalloc_optname_optval(temp, &dhcp_optflags[i], opt_name);
> -               putenv(*curr++);
> -               if (code == DHCP_SUBNET && temp[-OPT_DATA + OPT_LEN] == 4) {
> -                       /* Subnet option: make things like "$ip/$mask" possible */
> -                       uint32_t subnet;
> -                       move_from_unaligned32(subnet, temp);
> -                       *curr = xasprintf("mask=%u", mton(subnet));
> -                       putenv(*curr++);
> -               }
> - next:
> -               opt_name += strlen(opt_name) + 1;
> -               i++;
> -       }
> -       /* Export unknown options */
> -       for (i = 0; i < 256;) {
> -               BITMAP bitmap = FOUND_OPTS(i);
> -               if (!bitmap) {
> -                       i += BBITS;
> -                       continue;
> -               }
> -               if (bitmap & BMASK(i)) {
> -                       unsigned len, ofs;
> -
> -                       temp = udhcp_get_option(packet, i);
> -                       /* udhcp_get_option returns ptr to data portion,
> -                        * need to go back to get len
> -                        */
> -                       len = temp[-OPT_DATA + OPT_LEN];
> -                       *curr = xmalloc(sizeof("optNNN=") + 1 + len*2);
> -                       ofs = sprintf(*curr, "opt%u=", i);
> -                       *bin2hex(*curr + ofs, (void*) temp, len) = '\0';
> -                       putenv(*curr++);
> -               }
> -               i++;
> +               new_opt = xasprintf("sname=%."DHCP_PKT_SNAME_LEN_STR"s", packet->sname);
> +               putenvp(&envp, new_opt);
>         }
>
>         return envp;
> @@ -531,7 +507,7 @@ static char **fill_envp(struct dhcp_packet *packet)
>  /* Call a script with a par file and env vars */
>  static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
>  {
> -       char **envp, **curr;
> +       llist_t *envp;
>         char *argv[3];
>
>         envp = fill_envp(packet);
> @@ -543,11 +519,8 @@ static void udhcp_run_script(struct dhcp_packet *packet, const char *name)
>         argv[2] = NULL;
>         spawn_and_wait(argv);
>
> -       for (curr = envp; *curr; curr++) {
> -               log2(" %s", *curr);
> -               bb_unsetenv_and_free(*curr);
> -       }
> -       free(envp);
> +    /* Free all allocated environment variables */
> +       llist_free(envp, (void (*)(void *))bb_unsetenv_and_free);
>  }
>
>
> --
> 2.11.0
>
> _______________________________________________
> busybox mailing list
> busybox at busybox.net
> http://lists.busybox.net/mailman/listinfo/busybox


More information about the busybox mailing list