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Custom dhcp options #8571

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de32824
add custom dhcp options
bwjohns4 May 17, 2022
01ef879
revise size of dhcpCustomOffers[]
bwjohns4 May 17, 2022
647d0cd
Merge https://www.github.com/ESP8266/Arduino into customDHCPoptions
bwjohns4 May 20, 2022
287c78a
revised to do allocation in user code
bwjohns4 May 21, 2022
54d56d9
Merge https://www.github.com/ESP8266/Arduino into customDHCPoptions
bwjohns4 May 24, 2022
f9778c0
added error msg
bwjohns4 May 24, 2022
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51 changes: 51 additions & 0 deletions cores/esp8266/LwipDhcpServer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,7 @@

#include "user_interface.h"
#include "mem.h"
#include "Arduino.h"

typedef struct dhcps_state
{
Expand Down Expand Up @@ -536,6 +537,7 @@ void DhcpServer::send_offer(struct dhcps_msg* m)

end = add_msg_type(&m->options[4], DHCPOFFER);
end = add_offer_options(end);
end = insert_custom_offer_options(end, &m->options[0]);
end = add_end(end);

p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dhcps_msg), PBUF_RAM);
Expand Down Expand Up @@ -658,6 +660,7 @@ void DhcpServer::send_ack(struct dhcps_msg* m)

end = add_msg_type(&m->options[4], DHCPACK);
end = add_offer_options(end);
end = insert_custom_offer_options(end, &m->options[0]);
end = add_end(end);

p = pbuf_alloc(PBUF_TRANSPORT, sizeof(struct dhcps_msg), PBUF_RAM);
Expand Down Expand Up @@ -1591,3 +1594,51 @@ uint32 DhcpServer::dhcps_client_update(u8* bssid, struct ipv4_addr* ip)

return pdhcps_pool->ip.addr;
}

uint16 DhcpServer::add_dhcps_custom_options(uint8 offerCode, char *offerContent)
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using int8 or int16 generates more code than int on esp8266.
if 16 is important but not critical, we have int_fast16_t.
https://en.cppreference.com/w/c/types/integer

const char* is always preferred than char*

A comment may mention that the first bytes indicates the option length.

{
Serial.print("OfferCode: ");
Serial.println(String(offerCode)+offerContent);
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Here and below, debug code must be optional with #if DHCPS_DEBUG barriers and be using os_printf(),
like in other places in this file.

int sizeOfCustomOptions = strlen(dhcpCustomOffers);
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This name is misleading: sizeof generally means a constant which is the size of a type.
This name may be changed to lengthOfCustomOptions.

if (sizeOfCustomOptions + strlen(offerContent) + 1 < 100){
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Constants are generally forbidden in any code.
In this case 100 must be replaced by sizeof(dhcpCustomOffers).

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strlen(offerContent) seems to be invalid, since this is not a regular C-string.
Should it be offerContent[0] instead ?
(= length of the DHCP option)

dhcpCustomOffers[sizeOfCustomOptions] = offerCode;
dhcpCustomOffers[sizeOfCustomOptions +1] = strlen(offerContent);
for(int i = 0; i<(strlen(offerContent)); i++){
dhcpCustomOffers[sizeOfCustomOptions + 2 + i] = offerContent[i];
}
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You may simply want to use strcpy_P(&dhcpCustomOffers[sizeOfCustomOptions + 1], offerContent); ?
(using _P so user input can be in flash with PROGMEM / PSTR)

} else{
return 0;
}
return strlen(dhcpCustomOffers);
}

void DhcpServer::remove_dhcps_custom_options()
{
for(uint16 i = 0; i < 100; i++){
dhcpCustomOffers[i] = '\0';
}
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memset(dhcpCustomOffers, 0, sizeof(dhcpCustomOffers)) which is libc-optimized ?

}

uint8_t* DhcpServer::insert_custom_offer_options(uint8_t* optptr, uint8_t* optionsStart)
{
Serial.println("Adding Options");
Serial.println(dhcpCustomOffers);
int sizeOfCustomOptions = strlen(dhcpCustomOffers);
Serial.println(sizeOfCustomOptions);
uint16 i = 0;
while (i < sizeOfCustomOptions){
if((uint16(dhcpCustomOffers[i+1]) +1) < (uint16(312) - uint16(optptr - optionsStart))){
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casting to size_t is more efficient (casting to 16 or 8 bits produces larger code).

Serial.println("DHCP: Made it into IF:");
Serial.println((uint16(312) - uint16(optptr - optionsStart)));
for(int y = 0; y < uint16(dhcpCustomOffers[i+1]) + 2; y++){
*optptr++ = dhcpCustomOffers[i+y];
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memcpy(optptr, &dhcpCustomOffers[i+1], dhcpCustomOffers[i+1] + 1) ?

Serial.println(dhcpCustomOffers[i+y]);
}
}
else{
return optptr;
}
i += uint16(dhcpCustomOffers[i+1]) +2;
}
return optptr;
}
5 changes: 5 additions & 0 deletions cores/esp8266/LwipDhcpServer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,10 @@ class DhcpServer
bool reset_dhcps_lease_time(void);
uint32 get_dhcps_lease_time(void);
bool add_dhcps_lease(uint8* macaddr);
uint16 add_dhcps_custom_options(uint8 offerCode, char *offerContent);
void remove_dhcps_custom_options(void);
char dhcpCustomOffers[100];


void dhcps_set_dns(int num, const ipv4_addr_t* dns);

Expand All @@ -76,6 +80,7 @@ class DhcpServer
void node_remove_from_list(list_node** phead, list_node* pdelete);
uint8_t* add_msg_type(uint8_t* optptr, uint8_t type);
uint8_t* add_offer_options(uint8_t* optptr);
uint8_t* insert_custom_offer_options(uint8_t* optptr, uint8_t* optionsStart);
uint8_t* add_end(uint8_t* optptr);
void create_msg(struct dhcps_msg* m);
void send_offer(struct dhcps_msg* m);
Expand Down