Hostname not sent via DHCP request

[adydeac]

Hardware:

Board: ESP32 Dev Module
Core Installation version: 1.0.1
IDE name: Arduino IDE
Flash Frequency: 80Mhz
PSRAM enabled: no
Upload Speed: 115200
Computer OS: Debian

Description:

Hi,
I've noticed that somehow (I guess recently?) the hostname is not sent when making DHCP calls:

tcpdump -Anev -s 1024 -i br-lan port 67 or port 68 or port 69

tcpdump: listening on br-lan, link-type EN10MB (Ethernet), capture size 1024 bytes
01:22:43.011475 30:ae:a4:14:3f:e0 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 350: (tos 0x0, ttl 255, id 0, offset 0, flags [none], proto UDP (17), length 336)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 30:ae:a4:14:3f:e0, length 308, xid 0xaedfb4c4, Flags [none]
Client-Ethernet-Address 30:ae:a4:14:3f:e0
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Request
MSZ Option 57, length 2: 576
Requested-IP Option 50, length 4: 172.16.0.195
Parameter-Request Option 55, length 12:
Subnet-Mask, Default-Gateway, BR, Domain-Name-Server
Domain-Name, Netbios-Name-Server, Netbios-Node, Netbios-Scope
Router-Discovery, Static-Route, Classless-Static-Route, Vendor-Option
E..P.................D.C.<.}............................0...?...........................................................................................................................................................................................................c.Sc5..9..@2.....7......,./.!y+.........................................
01:22:43.014082 e8:de:27:6d:29:35 > 30:ae:a4:14:3f:e0, ethertype IPv4 (0x0800), length 342: (tos 0x0, ttl 64, id 7494, offset 0, flags [none], proto UDP (17), length 328)
172.16.0.1.67 > 172.16.0.195.68: BOOTP/DHCP, Reply, length 300, xid 0xaedfb4c4, Flags [none]
Your-IP 172.16.0.195
Server-IP 172.16.0.2
Client-Ethernet-Address 30:ae:a4:14:3f:e0
sname "tftp"
file "pxelinux.0"
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: ACK
Server-ID Option 54, length 4: 172.16.0.1
Lease-Time Option 51, length 4: 259200
RN Option 58, length 4: 129600
RB Option 59, length 4: 226800
Subnet-Mask Option 1, length 4: 255.255.255.0
BR Option 28, length 4: 172.16.0.255
Default-Gateway Option 3, length 4: 172.16.0.1
Domain-Name-Server Option 6, length 4: 172.16.0.1
Domain-Name Option 15, length 3: "lan"
E..H.F..@..{.........C.D.4Z*............................0...?...........tftp............................................................pxelinux.0......................................................................................................................c.Sc5..6.....3.....:....@;...u...........................lan....

This is the on the same router, but with an request from an android phone:

I am using the ESP-WROOM-32 chipset and Arduino IDE on Linux.

The code snippet is:

Sketch: (leave the backquotes for code formatting)

//Change the code below by your sketch
#include <Arduino.h>

void setup() {
  WiFi.begin(wifiSSID, wifiPass);
  nodeName = "shower-" + WiFi.macAddress();
  nodeName.replace(":", "");
  char _nodeName[20]; nodeName.toCharArray(_nodeName, 20);
  WiFi.setHostname(_nodeName);
  WiFi.mode(WIFI_STA);
}

void loop() {
}

[luisgcu]

@adydeac we have detected the same issue in project where we use a web server application, I think we detected the problem because we have several ESP32 in the same wifi network , we can't access the esp32's web-server application and we can't ping them on the network until they are connected for some time on the network(3-5minutes) and we believe that is caused because the esp32 exposes all the same host name "espressif" .. Anyone that can guide us on how to properly set the ESP32 host names ?

[lbernstone]

This probably should be looked at upstream. https://github.com/espressif/esp-idf/blob/master/components/lwip/port/esp32/netif/wlanif.c#L205. If you add this file into your sketch folder, you could write some code to give each machine a unique name.

[beegee-tokyo]

@luisgcu
Not a 100% sure if that is what you are looking for, but I give my ESP32's different names with

char _hostname[20];
uint8_t mac[6];
WiFi.macAddress(mac);
sprintf(_hostname, "esp32-%02x%02x%02x%02x%02x%02x", 
          mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
MDNS.begin(_hostname);

[atanisoft]

You can set the hostname before calling wifi.begin(). You just need to set the mode first. Then you should get a unique hostname.

[atanisoft]

@beegee-tokyo that only sets the mDNS advertised hostname and not the wifi hostname that shows up on the router. But that is good practice to set a unique hostname.

[adydeac]

As you can see from the tcpdump on the router (running openwrt, the gateway, the only DHCP server in the network), there is no hostname sent. Please see tha ascii dump as well. No "espressif" or anything. Something has changed maybe in the latest code? Or we need to enable the hostname sending?

[asetyde]

also with 1.0.2 RC1 ?

[adydeac]

Same.

[before update]
Thu Mar 7 11:07:45 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: authenticated
Thu Mar 7 11:07:45 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: associated (aid 2)
Thu Mar 7 11:07:45 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 WPA: pairwise key handshake completed (RSN)
Thu Mar 7 11:07:45 2019 daemon.info dnsmasq-dhcp[21458]: DHCPREQUEST(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0
Thu Mar 7 11:07:45 2019 daemon.info dnsmasq-dhcp[21458]: DHCPACK(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0
Thu Mar 7 11:08:01 2019 cron.info crond[893]: crond: USER root pid 22271 cmd /scripts/check_snmpd

[after update]
Thu Mar 7 11:09:29 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: authenticated
Thu Mar 7 11:09:29 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: associated (aid 2)
Thu Mar 7 11:09:29 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 WPA: pairwise key handshake completed (RSN)
Thu Mar 7 11:09:29 2019 daemon.info dnsmasq-dhcp[21458]: DHCPREQUEST(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0
Thu Mar 7 11:09:29 2019 daemon.info dnsmasq-dhcp[21458]: DHCPACK(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0

The code:
void startWiFi() {
WiFi.begin(wifiSSID, wifiPass);
nodeName = "shower-" + WiFi.macAddress();
nodeName.replace(":", "");
char _nodeName[20]; nodeName.toCharArray(_nodeName, 20);
#ifdef DEBUG
Serial.print("WiFi: MAC: "); Serial.println(WiFi.macAddress());
Serial.print("WiFi: setting hostname "); Serial.print(nodeName); Serial.println("...");
#endif
WiFi.setHostname(_nodeName);
tcpip_adapter_set_hostname(TCPIP_ADAPTER_IF_STA, _nodeName);
WiFi.mode(WIFI_STA);
}

Debug messages:
WiFi: MAC: 30:AE:A4:14:3F:E0
WiFi: setting hostname shower-30AEA4143FE0...

[atanisoft]

Move wifi.mode and wifi.sethostname before WiFi.begin. the call to tcpip adapter shouldn't be necessary as that is done inside the wifi library

[adydeac]

WiFi.mode(WIFI_STA);
nodeName = "shower-" + WiFi.macAddress();
nodeName.replace(":", "");
char _nodeName[20]; nodeName.toCharArray(_nodeName, 20);
#ifdef DEBUG
Serial.print("WiFi: MAC: "); Serial.println(WiFi.macAddress());
Serial.print("WiFi: setting hostname "); Serial.print(nodeName); Serial.println("...");
#endif
WiFi.setHostname(_nodeName);
//tcpip_adapter_set_hostname(TCPIP_ADAPTER_IF_STA, _nodeName);
WiFi.begin(wifiSSID, wifiPass);

Same:
Fri Mar 8 09:37:31 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: authenticated
Fri Mar 8 09:37:31 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 IEEE 802.11: associated (aid 2)
Fri Mar 8 09:37:31 2019 daemon.info hostapd: wlan0: STA 30:ae:a4:14:3f:e0 WPA: pairwise key handshake completed (RSN)
Fri Mar 8 09:37:31 2019 daemon.info dnsmasq-dhcp[21458]: DHCPREQUEST(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0
Fri Mar 8 09:37:31 2019 daemon.info dnsmasq-dhcp[21458]: DHCPACK(br-lan) 172.16.0.195 30:ae:a4:14:3f:e0

Probably you have noticed that not even the default "espressif" hostname is sent...

[lbernstone]

I don't know if toCharArray is mangling it somehow,but I have definitely seen invalid names (non-printable chars) come through while watching a tcpdump on the router. This is working for me:

  Serial.begin(115200);
  char hname[19]; // 5+12+1 - don't forget the \0
  snprintf(hname, 19, "ESP32-%012llX", ESP.getEfuseMac());  
  Serial.println(hname);
  WiFi.disconnect();
  WiFi.mode(WIFI_STA);
  WiFi.setHostname(hname);
  WiFi.begin("ssid","passwd");
  WiFi.waitForConnectResult();
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

[adydeac]

Same result:
rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:1100
load:0x40078000,len:10312
load:0x40080400,len:6460
entry 0x400806a4
ESP32-E03F14A4AE30
IP Address: 172.16.0.195

tcpdump -Anev -s 1024 -i br-lan port 67 or port 68 or port 69

10:15:57.942822 30:ae:a4:14:3f:e0 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 350: (tos 0x0, ttl 255, id 0, offset 0, flags [none], proto UDP (17), length 336)
0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from 30:ae:a4:14:3f:e0, length 308, xid 0x31888ad2, Flags [none]
Client-Ethernet-Address 30:ae:a4:14:3f:e0
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: Request
MSZ Option 57, length 2: 576
Requested-IP Option 50, length 4: 172.16.0.195
Parameter-Request Option 55, length 12:
Subnet-Mask, Default-Gateway, BR, Domain-Name-Server
Domain-Name, Netbios-Name-Server, Netbios-Node, Netbios-Scope
Router-Discovery, Static-Route, Classless-Static-Route, Vendor-Option
E..P.................D.C.<].....1.......................0...?...........................................................................................................................................................................................................c.Sc5..9..@2.....7......,./.!y+.........................................
10:15:57.945361 e8:de:27:6d:29:35 > 30:ae:a4:14:3f:e0, ethertype IPv4 (0x0800), length 342: (tos 0x0, ttl 64, id 7492, offset 0, flags [none], proto UDP (17), length 328)
172.16.0.1.67 > 172.16.0.195.68: BOOTP/DHCP, Reply, length 300, xid 0x31888ad2, Flags [none]
Your-IP 172.16.0.195
Server-IP 172.16.0.2
Client-Ethernet-Address 30:ae:a4:14:3f:e0
sname "tftp"
file "pxelinux.0"
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message Option 53, length 1: ACK
Server-ID Option 54, length 4: 172.16.0.1
Lease-Time Option 51, length 4: 259200
RN Option 58, length 4: 129600
RB Option 59, length 4: 226800
Subnet-Mask Option 1, length 4: 255.255.255.0
BR Option 28, length 4: 172.16.0.255
Default-Gateway Option 3, length 4: 172.16.0.1
Domain-Name-Server Option 6, length 4: 172.16.0.1
Domain-Name Option 15, length 3: "lan"
E..H.D..@..}.........C.D.4Z*....1.......................0...?...........tftp............................................................pxelinux.0......................................................................................................................c.Sc5..6.....3.....:....@;...u...........................lan....

I am using the latest dev libraries.

Am I doing something wrong? Is my board broken in any way?

[rpannekoek]

I'm having the same issue (using Wemos LOLIN D32 board). I have also tried every imaginable position of doing the setHostName call:

• After Wifi.mode(WIFI_STA) but before WiFi.begin
• After WiFi.begin
• Using an event handler (WiFi.onEvent) which triggers on the STA_START event

Whatever I try, the DHCP request sent by the ESP32 never contains a Host Name (DHCP Option 12), unlike for other devices (including ESP8266 boards) which do properly set their hostname.

As a result, the router (FritzBox) lists the WiFi device as "espressif" instead of the desired hostname (it's not clear to me where this "espressif" name comes from, because I don't see that anywhere in the DHCP Request either) and the built-in DNS server does not create a record for the hostname.

[rpannekoek]

Another (less important) issue: I'm creating libraries which work on both ESP8266 and ESP32. The API for setting hostname is currently different between ESP8266 and ESP32:

• ESP8266: WiFi.hostname() should be called before WiFi.begin
• ESP32: WiFi.setHostName() unclear where it should be called, but most reports mention after WiFi.begin (for example: Hostname and DNS #1259 )

[atanisoft]

@adydeac this may need to be moved to https://github.com/espressif/esp-idf as the DHCP implementation is implemented there (in the lwip stack actually).

[adydeac]

I'm not very familiar with esp-idf project. Is it another fork? Is it an substitute? Is it part of this project?

[atanisoft]

I'm not very familiar with esp-idf project. Is it another fork? Is it an substitute? Is it part of this project?

It provides most of the underlying functionality of this project.

[maxdd]

As Ibernstone suggested i was able to make it work like this

    char hname[19];
    snprintf(hname, 12, "ESP%d-LIGHT", 32);
    WiFi.disconnect();
    WiFi.mode(WIFI_STA);
    WiFi.setHostname(hname);
    WiFi.begin(WIFI_SSID, WIFI_PSK);

It really seems to be related to '\0'.
I've also tried like this

char hname[12] = "ESP32-LIGHT";
hname[11] = '\0';

and it also works

[stickbreaker]

@maxdd you should not need this two step process to declare a string:

char hname[12] = "ESP32-LIGHT";
hname[11] = '\0';

this is all you need:

char hname[] = "ESP32-LIGHT"; // the compiler will append a null automagically. 

Your declaration worked because the compiler did append a null, else it would complain about type mismatch. If you changed the declaration to 13 characters (char hname[13]) the compiler would have complained because of a type mis-match. eleven characters between the quotes and the automagic null is only 12, so you get a type mismatch.

Chuck.

[maxdd]

That's curious, last time a tried your "normal/standard" solution it didnt work.
Now it does, probably i overlooked something due to the late hours.

[rpannekoek]

Still no success for me if I perform the WiFi calls in the sequence given by @maxdd
BTW, WiFi.disconnect() returns false if I execute it before WiFi.mode(WIFI_STA), which makes sense if I look at its implementation (it does basically nothing in that case):

[lbernstone]

WiFi.disconnect is there to make sure the device releases its lease (and clears the info out of nvs). hostname is not given (or requested) on a lease renewal/validation. Both the esp32 and the dhcp server need to see this as a new event. Ultimately, it is up to the dhcp server to report new dns names, so there will be many situations where this will never work.

[atanisoft]

Wifi.mode() is required for the disconnect method to do any clearing of NVS IIRC

[nightvisi0n]

I could successfully reproduce that this is a real bug and I created a PR in order to fix it: espressif/esp-lwip#6

The underlying issue has nothing to do with any \0 escaping (just because this was told to be a fix in some comments above) and is rather a different bug/side-effect.

This bug is a little bit tricky, because it doesn't appear in every operational state. If the in-memory stored previous dhcp lease is e.g. no longer valid there will also be a fresh dhcp request (and hostname propagation). That's maybe the reason why it worked for some of you "sometimes".

@luisgcu @rpannekoek You can verify if you are really experiencing the same bug by erasing the complete flash of the esp32 (which in turn clears any previous dhcp lease, leading to a fresh dhcp lease and an updated hostname). This can be done e.g. with esptool or platformio (pio run -t erase).

[jeroenst]

I can confirm this bug.

dnsmasq logging with ESP8266:
Jul 4 20:53:53 server dnsmasq-dhcp[940]: 1777019338 DHCPACK(enp3s0.2) 192.168.10.143 84:f3:eb:58:29:63 ESP_SMARTMETER

dnsmasq logging with ESP32:
Jul 4 20:51:58 server dnsmasq-dhcp[940]: 758037265 DHCPACK(enp3s0.2) 192.168.10.106 24:0a:c4:96:48:ac

See the missing hostname in the logging of dnsmasq.... Hostname is set for sure btw.

[jeroenst]

WORKAROUND:

Add
WiFi.config(INADDR_NONE, INADDR_NONE, INADDR_NONE);
WiFi.setHostname(_hostname.c_str());
before
WiFi.begin();

I hope issue will be resolved soon.

[evert-arias]

The workaround suggested by @jeroenst worked for me!

[BozoTClown]

After working on this issue for over 4 hours @jeroenst suggestion work for me also. My ESP8266 was not this difficult to do. Thank you very much.

WiFi.config(INADDR_NONE, INADDR_NONE, INADDR_NONE);
WiFi.setHostname(mqtt_device_id);
WiFi.begin(ssid, password);

[stacklover]

I just resolved same issue by using @jeroenst suggestion! Sigh!
(on ESP32)

[mvadu]

I can confirm it too.. With WiFi.config(INADDR_NONE, INADDR_NONE, INADDR_NONE); before WiFi.begin(ssid, password); works as expected, and on DHCP side I see these requests now

23 00:26:32 dnsmasq-dhcp[260]: DHCPDISCOVER(br0) xx:xx:xx:xx:xx:xx 
Feb 23 00:26:32 dnsmasq-dhcp[260]: DHCPOFFER(br0) a.b.c.d xx:xx:xx:xx:xx:xx 
Feb 23 00:26:32 dnsmasq-dhcp[260]: DHCPREQUEST(br0) a.b.c.d xx:xx:xx:xx:xx:xx 
Feb 23 00:26:32 dnsmasq-dhcp[260]: DHCPACK(br0) a.b.c.d xx:xx:xx:xx:xx:xx HostName

[Bliph]

Just a note about ArduinoOTA:

The default behaviour of ESP32 ArduinoOTA is to set the hostname to 'esp32-', and this interferes with the workaround. Most examples on the net for ESP32 OTA instructs to use IP-address, so I couldn't find a solution to this problem (maybe I'm ignorant) until i looked at the ArduinoOTA source code. To fix this, manually set the hostname in the OTA-object:

ArduinoOTA.setHostname(device);    // Same as in WiFi.setHostname(device);
ArduinoOTA.begin();

An alternative solution (presumes tha MDNS is already configured):

ArduinoOTA.setMdnsEnabled(false);
ArduinoOTA.begin();

[stale]

[STALE_SET] This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[vshymanskyy]

Wake up, Neo.

[stale]

[STALE_CLR] This issue has been removed from the stale queue. Please ensure activity to keep it openin the future.

[stale]

[STALE_SET] This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[mvadu]

knock knock

[stale]

[STALE_CLR] This issue has been removed from the stale queue. Please ensure activity to keep it openin the future.

[SuGlider]

Check PR #6659