ref: d-a-v/esp82xx-nonos-linklayer#31
origin: #5902me-no-dev/ESPAsyncTCP#108
Following the links above is instructive.
To summarize:
* currently and from a long time lwIP tcp client connections always uses the same tcp source port number right after boot
* this port number is increased everytime a new one is needed (= new tcp client connection)
(to be noted, linux has the same increasing behavior)
* when connecting to the same server (right after boot), the triplet (esp-ip-address, source port, destination port) are the same, and may hit remote server list of sockets in time-wait-state (previous connection unproperly closed from the same esp). Consequently the new connection fails when it happens.
* this is happening only when debugging (esp reboots often, in less time than time-wait expiration), so the nasty effect is amplified especially when bugs are being chased
* efforts had been done when espressif's lwIP implementation wasn't open source, with WiFiClient::setLocalPortStart() #632 but it must be explicitely called with a different random number at every reboot. Efficient but not ideal.
This PR uses espressif firmware's r_rand() everytime a new local source port is needed. A different source port number is now showed by tcpdump right after boot. Source port range and duplication is verified everytime in lwIP's src/core/tcp.c:tcp_new_port(). It is implemented as a local patch for upstream lwIP so it is valid not only with WiFiClient but also with @me-no-dev's Async libraries (they don't use WiFiClient).
WiFiClient::setLocalPortStart() is still usable with the same effects as before.
* lwip2: better handling of ipv4_addr/t type + 3 sntp servers
* bump lwip2 version
* Only with FEATURES=1: 3 sntp servers and AutoIP enabled (169.254 when dhcp server fails)
* Only with FEATURES=1: 3 sntp servers and AutoIP enabled (169.254 when dhcp server fails)
* local CI runner: select build type
* new ipv4_addr/t definition makes things easier for IPAddress
* update local CI runner
* lwip2 changes
* lwip2: port esp-ping and espconn
* interactive example: update with option for using DHCP again after using static IP
* lwip2: avoid crash when IP address is set to 0(any) by dhcp not getting its lease renewal in due time
* lwip2: automatically remove oldest PCBs in time-wait state, limit their number
thanks to @me-no-dev 07f4d4c241 (diff-f8258e71e25fb9985ca3799e3d8b88ecR399)
* faq: update about tcpCleanup()
* lwip2: add a macro HAS_PHY_CAPTURE=1 indicating capture facility is available
