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1f86ecb72

Martin Lewis
Martin Lewis
2020-06-29
SUCCESS Duration: 151s

Subject

udhcpc: fix a TODO in fill_envp using option scanner

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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networking/udhcp/dhcpc.c +84 -114
networking/udhcp/dhcpc.c+84 -114
@@ -386,59 +386,78 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
return ret;
}
-/* put all the parameters into the environment */
-static char **fill_envp(struct dhcp_packet *packet)
+static void putenvp(llist_t **envp, char *new_opt)
+{
+ putenv(new_opt);
+ log2(" %s", new_opt);
+ llist_add_to(envp, new_opt);
+}
+
+static const char* get_optname(uint8_t code, const struct dhcp_optflag **dh)
{
- 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
+ /* 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.
*/
- 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);
+ for (*dh = dhcp_optflags; (*dh)->code && (*dh)->code < code; (*dh)++)
+ continue;
+
+ if ((*dh)->code == code)
+ return nth_string(dhcp_option_strings, (*dh - dhcp_optflags));
- *curr = xasprintf("interface=%s", client_data.interface);
- putenv(*curr++);
+ return NULL;
+}
+
+/* put all the parameters into the environment */
+static llist_t *fill_envp(struct dhcp_packet *packet)
+{
+ uint8_t *optptr;
+ struct dhcp_scan_state scan_state;
+ char *new_opt;
+ llist_t *envp = NULL;
+
+ putenvp(&envp, xasprintf("interface=%s", client_data.interface));
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) {
+ const struct dhcp_optflag *dh;
+ const char *opt_name;
+ uint8_t code = optptr[OPT_CODE];
+ uint8_t len = optptr[OPT_LEN];
+ uint8_t *data = optptr + OPT_DATA;
+
+ opt_name = get_optname(code, &dh);
+ if (opt_name) {
+ new_opt = xmalloc_optname_optval(data, dh, opt_name);
+ if (code == DHCP_SUBNET && len == 4) {
+ uint32_t subnet;
+ putenvp(&envp, new_opt);
+ move_from_unaligned32(subnet, data);
+ new_opt = xasprintf("mask=%u", mton(subnet));
+ }
+ } else {
+ 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] = '\0';
+ }
+ 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 +471,31 @@ 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 +504,7 @@ 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 +516,8 @@ 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);
}