How to split check sum processing from udp_send()

[gunt2551]

My audio project cannot use udp.endPacket() from WiFiUdp.h, which takes too long for one processing.
So, I want to split processing check sum from udp_send(), by doing manual check sum and sending a packet.

I found these functions in tools/sdk/lwip2/include/lwip/udp.h, which cannot call because LWIP_CHECKSUM_ON_COPY is set 0 by default, according #include "lwip/opt.h".
I tried to set it to 1 but it seems there are no funtions in assembly file. Is there anyway to use these functions?

#if LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_UDP
err_t            udp_sendto_if_chksum(struct udp_pcb *pcb, struct pbuf *p,
                                 const ip_addr_t *dst_ip, u16_t dst_port,
                                 struct netif *netif, u8_t have_chksum,
                                 u16_t chksum);
err_t            udp_sendto_chksum(struct udp_pcb *pcb, struct pbuf *p,
                                 const ip_addr_t *dst_ip, u16_t dst_port,
                                 u8_t have_chksum, u16_t chksum);
err_t            udp_send_chksum(struct udp_pcb *pcb, struct pbuf *p,
                                 u8_t have_chksum, u16_t chksum);
err_t            udp_sendto_if_src_chksum(struct udp_pcb *pcb, struct pbuf *p,
                                 const ip_addr_t *dst_ip, u16_t dst_port, struct netif *netif,
                                 u8_t have_chksum, u16_t chksum, const ip_addr_t *src_ip);
#endif /* LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_UDP */

checking functions that are exist in assembly file or not.
so, you can see udp_send<...>_chksum are missing.
I use command promt for checking udp_send

"%LocalAppData%\Arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.1.0-gcc10.3-e5f9fec\bin\xtensa-lx106-elf-nm.exe" "%LocalAppData%\Arduino15\packages\esp8266\hardware\esp8266\3.1.2\tools\sdk\lib\liblwip2-536-feat.a" | findstr "udp_send"

         U espconn_udp_sendto
00000044 T espconn_udp_sendto
         U udp_send
         U udp_sendto
         U udp_sendto
00000004 T udp_send
00000018 T udp_sendto
00000004 T udp_sendto_if
0000002c T udp_sendto_if_src
         U udp_sendto_if
         U udp_sendto_if_src
         U udp_sendto

searching chksum | findstr "chksum"

         U inet_chksum
inet_chksum.o:
00000004 T inet_chksum
00000004 T inet_chksum_pbuf
0000000c T inet_chksum_pseudo
0000000c T inet_chksum_pseudo_partial
00000004 T ip_chksum_pseudo
00000004 T ip_chksum_pseudo_partial
00000000 T lwip_standard_chksum
         U ip_chksum_pseudo
         U ip_chksum_pseudo
         U ip_chksum_pseudo
         U inet_chksum
         U inet_chksum_pbuf
         U inet_chksum
         U inet_chksum
         U inet_chksum

[mcspr]

I found these functions in tools/sdk/lwip2/include/lwip/udp.h, which cannot call because LWIP_CHECKSUM_ON_COPY is set 0 by default, according #include "lwip/opt.h".
I tried to set it to 1 but it seems there are no funtions in assembly file. Is there anyway to use these functions?

See tools/sdk/lwip2/README.md and https://github.com/d-a-v/esp82xx-nonos-linklayer

Our build rules only cover Core files, Arduino libs and the sketch itself. Everything else is pre-built, you must manually build & install updated lwip .a & .h for these symbols to appear. While WSL could be a bit slow due to the WSL <-> Windows filesystem ops, I'd imagine it would be the fastest way to do this.

Also note that the preferred way is to edit builder/glue-lwip/arduino/lwipopts.h, not opts.h. make would later copy it to the tools/sdk/lwip2/include

# builder uses tools relative to itself, not the ones in $PATH
# locate /mnt/c/Users/YOU/AppData/Local/Arduino15/packages/esp8266/
$ cd tools/
$ python get.py
# builds & installs files to the dir above
$ cd sdk/lwip2
$ make -C builder -f Makefile.arduino install

(or, try cmake & -G Ninja. pretty sure it works even without windows dev tools install, just grab both cmake and ninja via winget and figure out the correct esp8266 package paths)