dhcpd: remember and record hostnames; optimize get_option

dumpleases: show hostnames

function                                             old     new   delta
add_lease                                            230     292     +62
send_offer                                           403     421     +18
send_ACK                                             232     249     +17
read_leases                                          249     258      +9
dumpleases_main                                      604     609      +5
nobody_responds_to_arp                                84      86      +2
udhcp_end_option                                      32      30      -2
udhcp_get_option                                     222     171     -51
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 6/2 up/down: 113/-53)            Total: 60 bytes

8 files changed, 149 insertions, 124 deletions

diff --git a/networking/udhcp/dhcpd.h b/networking/udhcp/dhcpd.h
index 02e392aaf..b4e180882 100644
--- a/networking/udhcp/dhcpd.h
+++ b/networking/udhcp/dhcpd.h
@@ -74,8 +74,6 @@ struct server_config_t {
 #define SERVER_PORT 67
 #endif
 
-extern struct dhcpOfferedAddr *leases;
-
 
 /*** leases.h ***/
 
@@ -92,9 +90,15 @@ struct dhcpOfferedAddr {
          * and optionally adjusted (current time subtracted)
          * if server_config.remaining = 1 */
         leasetime_t expires;
+        uint8_t hostname[20]; /* (size is a multiply of 4) */
 };
 
-struct dhcpOfferedAddr *add_lease(const uint8_t *chaddr, uint32_t yiaddr, leasetime_t leasetime) FAST_FUNC;
+extern struct dhcpOfferedAddr *leases;
+
+struct dhcpOfferedAddr *add_lease(
+                const uint8_t *chaddr, uint32_t yiaddr,
+                leasetime_t leasetime, uint8_t *hostname
+                ) FAST_FUNC;
 int lease_expired(struct dhcpOfferedAddr *lease) FAST_FUNC;
 struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr) FAST_FUNC;
 struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr) FAST_FUNC;
diff --git a/networking/udhcp/dumpleases.c b/networking/udhcp/dumpleases.c
index c0d515d28..1558f8848 100644
--- a/networking/udhcp/dumpleases.c
+++ b/networking/udhcp/dumpleases.c
@@ -47,8 +47,9 @@ int dumpleases_main(int argc UNUSED_PARAM, char **argv)
 
         fd = xopen(file, O_RDONLY);
 
-        printf("Mac Address       IP-Address      Expires %s\n", (opt & OPT_a) ? "at" : "in");
-        /*     "00:00:00:00:00:00 255.255.255.255 Wed Jun 30 21:49:08 1993" */
+        printf("Mac Address       IP Address      Host Name           Expires %s\n", (opt & OPT_a) ? "at" : "in");
+        /*     "00:00:00:00:00:00 255.255.255.255 ABCDEFGHIJKLMNOPQRS Wed Jun 30 21:49:08 1993" */
+        /*     "123456789 123456789 123456789 123456789 123456789 123456789 123456789 123456789 */
 
         if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at))
                 return 0;
@@ -64,7 +65,9 @@ int dumpleases_main(int argc UNUSED_PARAM, char **argv)
                         fmt = ":%02x";
                 }
                 addr.s_addr = lease.yiaddr;
-                printf(" %-15s ", inet_ntoa(addr));
+                /* actually, 15+1 and 19+1, +1 is a space between columns */
+                /* lease.hostname is char[20] and is always NUL terminated */
+                printf(" %-16s%-20s", inet_ntoa(addr), lease.hostname);
                 expires_abs = ntohl(lease.expires) + written_at;
                 if (expires_abs <= curr) {
                         puts("expired");
diff --git a/networking/udhcp/files.c b/networking/udhcp/files.c
index fb6fe01ae..a061a9c9b 100644
--- a/networking/udhcp/files.c
+++ b/networking/udhcp/files.c
@@ -420,7 +420,7 @@ void FAST_FUNC read_leases(const char *file)
                                 continue;
                         /* NB: add_lease takes "relative time", IOW,
                          * lease duration, not lease deadline. */
-                        if (!(add_lease(lease.chaddr, lease.yiaddr, expires))) {
+                        if (!(add_lease(lease.chaddr, lease.yiaddr, expires, lease.hostname))) {
                                 bb_error_msg("too many leases while loading %s", file);
                                 break;
                         }
diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
index 3044c2040..d62f32471 100644
--- a/networking/udhcp/leases.c
+++ b/networking/udhcp/leases.c
@@ -48,9 +48,12 @@ static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
 
 
 /* Add a lease into the table, clearing out any old ones */
-struct dhcpOfferedAddr* FAST_FUNC add_lease(const uint8_t *chaddr, uint32_t yiaddr, leasetime_t leasetime)
+struct dhcpOfferedAddr* FAST_FUNC add_lease(
+                const uint8_t *chaddr, uint32_t yiaddr,
+                leasetime_t leasetime, uint8_t *hostname)
 {
         struct dhcpOfferedAddr *oldest;
+        uint8_t hostname_length;
 
         /* clean out any old ones */
         clear_lease(chaddr, yiaddr);
@@ -58,6 +61,19 @@ struct dhcpOfferedAddr* FAST_FUNC add_lease(const uint8_t *chaddr, uint32_t yiad
         oldest = oldest_expired_lease();
 
         if (oldest) {
+                oldest->hostname[0] = '\0';
+                if (hostname) {
+                        hostname_length = hostname[-1]; /* look at option size byte */
+                        if (hostname_length > sizeof(oldest->hostname))
+                                hostname_length = sizeof(oldest->hostname);
+                        hostname = (uint8_t*) safe_strncpy((char*)oldest->hostname, (char*)hostname, hostname_length);
+                        /* sanitization (s/non-ACSII/^/g) */
+                        while (*hostname) {
+                                if (*hostname < ' ' || *hostname > 126)
+                                        *hostname = '^';
+                                hostname++;
+                        }
+                }
                 memcpy(oldest->chaddr, chaddr, 16);
                 oldest->yiaddr = yiaddr;
                 oldest->expires = time(NULL) + leasetime;
@@ -117,7 +133,7 @@ static int nobody_responds_to_arp(uint32_t addr)
         temp.s_addr = addr;
         bb_info_msg("%s belongs to someone, reserving it for %u seconds",
                 inet_ntoa(temp), (unsigned)server_config.conflict_time);
-        add_lease(blank_chaddr, addr, server_config.conflict_time);
+        add_lease(blank_chaddr, addr, server_config.conflict_time, NULL);
         return 0;
 }
 
diff --git a/networking/udhcp/options.c b/networking/udhcp/options.c
index 581a7b671..143a1fd1c 100644
--- a/networking/udhcp/options.c
+++ b/networking/udhcp/options.c
@@ -119,58 +119,61 @@ const uint8_t dhcp_option_lengths[] ALIGN1 = {
 };
 
 
-/* get an option with bounds checking (warning, not aligned). */
+/* get an option with bounds checking (warning, result is not aligned). */
 uint8_t* FAST_FUNC get_option(struct dhcpMessage *packet, int code)
 {
-        int i, length;
         uint8_t *optionptr;
-        int over = 0;
-        int curr = OPTION_FIELD;
-
+        int len;
+        int rem;
+        int overload = 0;
+        enum {
+                FILE_FIELD101  = FILE_FIELD  * 0x101,
+                SNAME_FIELD101 = SNAME_FIELD * 0x101,
+        };
+
+        /* option bytes: [code][len][data1][data2]..[dataLEN] */
         optionptr = packet->options;
-        i = 0;
-        length = sizeof(packet->options);
+        rem = sizeof(packet->options);
         while (1) {
-                if (i >= length) {
-                        bb_error_msg("bogus packet, option fields too long");
+                if (rem <= 0) {
+                        bb_error_msg("bogus packet, malformed option field");
                         return NULL;
                 }
-                if (optionptr[i + OPT_CODE] == code) {
-                        if (i + 1 + optionptr[i + OPT_LEN] >= length) {
-                                bb_error_msg("bogus packet, option fields too long");
-                                return NULL;
-                        }
-                        return optionptr + i + 2;
+                if (optionptr[OPT_CODE] == DHCP_PADDING) {
+                        rem--;
+                        optionptr++;
+                        continue;
                 }
-                switch (optionptr[i + OPT_CODE]) {
-                case DHCP_PADDING:
-                        i++;
-                        break;
-                case DHCP_OPTION_OVER:
-                        if (i + 1 + optionptr[i + OPT_LEN] >= length) {
-                                bb_error_msg("bogus packet, option fields too long");
-                                return NULL;
-                        }
-                        over = optionptr[i + 3];
-                        i += optionptr[OPT_LEN] + 2;
-                        break;
-                case DHCP_END:
-                        if (curr == OPTION_FIELD && (over & FILE_FIELD)) {
+                if (optionptr[OPT_CODE] == DHCP_END) {
+                        if ((overload & FILE_FIELD101) == FILE_FIELD) {
+                                /* can use packet->file, and didn't look at it yet */
+                                overload |= FILE_FIELD101; /* "we looked at it" */
                                 optionptr = packet->file;
-                                i = 0;
-                                length = sizeof(packet->file);
-                                curr = FILE_FIELD;
-                        } else if (curr == FILE_FIELD && (over & SNAME_FIELD)) {
+                                rem = sizeof(packet->file);
+                                continue;
+                        }
+                        if ((overload & SNAME_FIELD101) == SNAME_FIELD) {
+                                /* can use packet->sname, and didn't look at it yet */
+                                overload |= SNAME_FIELD101; /* "we looked at it" */
                                 optionptr = packet->sname;
-                                i = 0;
-                                length = sizeof(packet->sname);
-                                curr = SNAME_FIELD;
-                        } else
-                                return NULL;
-                        break;
-                default:
-                        i += optionptr[OPT_LEN + i] + 2;
+                                rem = sizeof(packet->sname);
+                                continue;
+                        }
+                        return NULL;
+                }
+                len = 2 + optionptr[OPT_LEN];
+                rem -= len;
+                if (rem < 0)
+                        continue; /* complain and return NULL */
+
+                if (optionptr[OPT_CODE] == code)
+                        return optionptr + OPT_DATA;
+
+                if (optionptr[OPT_CODE] == DHCP_OPTION_OVERLOAD) {
+                        overload |= optionptr[OPT_DATA];
+                        /* fall through */
                 }
+                optionptr += len;
         }
         return NULL;
 }
@@ -182,17 +185,16 @@ int FAST_FUNC end_option(uint8_t *optionptr)
         int i = 0;
 
         while (optionptr[i] != DHCP_END) {
-                if (optionptr[i] == DHCP_PADDING)
-                        i++;
-                else
-                        i += optionptr[i + OPT_LEN] + 2;
+                if (optionptr[i] != DHCP_PADDING)
+                        i += optionptr[i + OPT_LEN] + 1;
+                i++;
         }
         return i;
 }
 
 
-/* add an option string to the options (an option string contains an option code,
- * length, then data) */
+/* add an option string to the options */
+/* option bytes: [code][len][data1][data2]..[dataLEN] */
 int FAST_FUNC add_option_string(uint8_t *optionptr, uint8_t *string)
 {
         int end = end_option(optionptr);
diff --git a/networking/udhcp/options.h b/networking/udhcp/options.h
index d18a353d0..87440c30c 100644
--- a/networking/udhcp/options.h
+++ b/networking/udhcp/options.h
@@ -7,7 +7,7 @@
 # pragma GCC visibility push(hidden)
 #endif
 
-#define TYPE_MASK       0x0F
+#define TYPE_MASK       0x0F
 
 enum {
         OPTION_IP = 1,
@@ -24,8 +24,8 @@ enum {
         OPTION_S32
 };
 
-#define OPTION_REQ      0x10 /* have the client request this option */
-#define OPTION_LIST     0x20 /* There can be a list of 1 or more of these */
+#define OPTION_REQ      0x10 /* have the client request this option */
+#define OPTION_LIST     0x20 /* There can be a list of 1 or more of these */
 
 /*****************************************************************/
 /* Do not modify below here unless you know what you are doing!! */
@@ -34,67 +34,64 @@ enum {
 /* DHCP protocol -- see RFC 2131 */
 #define DHCP_MAGIC              0x63825363
 
-
 /* DHCP option codes (partial list) */
-#define DHCP_PADDING            0x00
-#define DHCP_SUBNET             0x01
-#define DHCP_TIME_OFFSET        0x02
-#define DHCP_ROUTER             0x03
-#define DHCP_TIME_SERVER        0x04
-#define DHCP_NAME_SERVER        0x05
-#define DHCP_DNS_SERVER         0x06
-#define DHCP_LOG_SERVER         0x07
-#define DHCP_COOKIE_SERVER      0x08
-#define DHCP_LPR_SERVER         0x09
-#define DHCP_HOST_NAME          0x0c
-#define DHCP_BOOT_SIZE          0x0d
-#define DHCP_DOMAIN_NAME        0x0f
-#define DHCP_SWAP_SERVER        0x10
-#define DHCP_ROOT_PATH          0x11
-#define DHCP_IP_TTL             0x17
-#define DHCP_MTU                0x1a
-#define DHCP_BROADCAST          0x1c
-#define DHCP_NTP_SERVER         0x2a
-#define DHCP_WINS_SERVER        0x2c
-#define DHCP_REQUESTED_IP       0x32
-#define DHCP_LEASE_TIME         0x33
-#define DHCP_OPTION_OVER        0x34
-#define DHCP_MESSAGE_TYPE       0x35
-#define DHCP_SERVER_ID          0x36
-#define DHCP_PARAM_REQ          0x37
-#define DHCP_MESSAGE            0x38
-#define DHCP_MAX_SIZE           0x39
-#define DHCP_T1                 0x3a
-#define DHCP_T2                 0x3b
-#define DHCP_VENDOR             0x3c
-#define DHCP_CLIENT_ID          0x3d
-#define DHCP_FQDN               0x51
-#define DHCP_END                0xFF
-
-
-#define BOOTREQUEST             1
-#define BOOTREPLY               2
-
-#define ETH_10MB                1
-#define ETH_10MB_LEN            6
-
-#define DHCPDISCOVER            1 /* client -> server */
-#define DHCPOFFER               2 /* client <- server */
-#define DHCPREQUEST             3 /* client -> server */
-#define DHCPDECLINE             4 /* client -> server */
-#define DHCPACK                 5 /* client <- server */
-#define DHCPNAK                 6 /* client <- server */
-#define DHCPRELEASE             7 /* client -> server */
-#define DHCPINFORM              8 /* client -> server */
-
-#define OPTION_FIELD            0
-#define FILE_FIELD              1
-#define SNAME_FIELD             2
-
-/* miscellaneous defines */
-#define OPT_CODE 0
-#define OPT_LEN 1
-#define OPT_DATA 2
+#define DHCP_PADDING            0x00
+#define DHCP_SUBNET             0x01
+#define DHCP_TIME_OFFSET        0x02
+#define DHCP_ROUTER             0x03
+#define DHCP_TIME_SERVER        0x04
+#define DHCP_NAME_SERVER        0x05
+#define DHCP_DNS_SERVER         0x06
+#define DHCP_LOG_SERVER         0x07
+#define DHCP_COOKIE_SERVER      0x08
+#define DHCP_LPR_SERVER         0x09
+#define DHCP_HOST_NAME          0x0c
+#define DHCP_BOOT_SIZE          0x0d
+#define DHCP_DOMAIN_NAME        0x0f
+#define DHCP_SWAP_SERVER        0x10
+#define DHCP_ROOT_PATH          0x11
+#define DHCP_IP_TTL             0x17
+#define DHCP_MTU                0x1a
+#define DHCP_BROADCAST          0x1c
+#define DHCP_NTP_SERVER         0x2a
+#define DHCP_WINS_SERVER        0x2c
+#define DHCP_REQUESTED_IP       0x32
+#define DHCP_LEASE_TIME         0x33
+#define DHCP_OPTION_OVERLOAD    0x34
+#define DHCP_MESSAGE_TYPE       0x35
+#define DHCP_SERVER_ID          0x36
+#define DHCP_PARAM_REQ          0x37
+#define DHCP_MESSAGE            0x38
+#define DHCP_MAX_SIZE           0x39
+#define DHCP_T1                 0x3a
+#define DHCP_T2                 0x3b
+#define DHCP_VENDOR             0x3c
+#define DHCP_CLIENT_ID          0x3d
+#define DHCP_FQDN               0x51
+#define DHCP_END                0xFF
+/* Offsets in option byte sequence */
+#define OPT_CODE                0
+#define OPT_LEN                 1
+#define OPT_DATA                2
+/* Bits in "overload" option */
+#define OPTION_FIELD            0
+#define FILE_FIELD              1
+#define SNAME_FIELD             2
+
+#define BOOTREQUEST             1
+#define BOOTREPLY               2
+
+#define ETH_10MB                1
+#define ETH_10MB_LEN            6
+
+#define DHCPDISCOVER            1 /* client -> server */
+#define DHCPOFFER               2 /* client <- server */
+#define DHCPREQUEST             3 /* client -> server */
+#define DHCPDECLINE             4 /* client -> server */
+#define DHCPACK                 5 /* client <- server */
+#define DHCPNAK                 6 /* client <- server */
+#define DHCPRELEASE             7 /* client -> server */
+#define DHCPINFORM              8 /* client -> server */
 
 struct dhcp_option {
         uint8_t flags;
diff --git a/networking/udhcp/script.c b/networking/udhcp/script.c
index 5d42a45db..3029b1367 100644
--- a/networking/udhcp/script.c
+++ b/networking/udhcp/script.c
@@ -135,7 +135,7 @@ static char **fill_envp(struct dhcpMessage *packet)
         char **envp, **curr;
         const char *opt_name;
         uint8_t *temp;
-        char over = 0;
+        uint8_t over = 0;
 
         if (packet) {
                 for (i = 0; dhcp_options[i].code; i++) {
@@ -147,7 +147,7 @@ static char **fill_envp(struct dhcpMessage *packet)
                 }
                 if (packet->siaddr)
                         num_options++;
-                temp = get_option(packet, DHCP_OPTION_OVER);
+                temp = get_option(packet, DHCP_OPTION_OVERLOAD);
                 if (temp)
                         over = *temp;
                 if (!(over & FILE_FIELD) && packet->file[0])
diff --git a/networking/udhcp/serverpacket.c b/networking/udhcp/serverpacket.c
index afc0fb40d..8b0f1856b 100644
--- a/networking/udhcp/serverpacket.c
+++ b/networking/udhcp/serverpacket.c
@@ -105,7 +105,7 @@ int FAST_FUNC send_offer(struct dhcpMessage *oldpacket)
         uint32_t req_align;
         uint32_t lease_time_aligned = server_config.lease;
         uint32_t static_lease_ip;
-        uint8_t *req, *lease_time;
+        uint8_t *req, *lease_time, *p_host_name;
         struct option_set *curr;
         struct in_addr addr;
 
@@ -146,7 +146,8 @@ int FAST_FUNC send_offer(struct dhcpMessage *oldpacket)
                         bb_error_msg("no IP addresses to give - OFFER abandoned");
                         return -1;
                 }
-                if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
+                p_host_name = get_option(oldpacket, DHCP_HOST_NAME);
+                if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time, p_host_name)) {
                         bb_error_msg("lease pool is full - OFFER abandoned");
                         return -1;
                 }
@@ -201,6 +202,7 @@ int FAST_FUNC send_ACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
         uint8_t *lease_time;
         uint32_t lease_time_aligned = server_config.lease;
         struct in_addr addr;
+        uint8_t *p_host_name;
 
         init_packet(&packet, oldpacket, DHCPACK);
         packet.yiaddr = yiaddr;
@@ -232,7 +234,8 @@ int FAST_FUNC send_ACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
         if (send_packet(&packet, 0) < 0)
                 return -1;
 
-        add_lease(packet.chaddr, packet.yiaddr, lease_time_aligned);
+        p_host_name = get_option(oldpacket, DHCP_HOST_NAME);
+        add_lease(packet.chaddr, packet.yiaddr, lease_time_aligned, p_host_name);
         if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
                 /* rewrite the file with leases at every new acceptance */
                 write_leases();