// SPDX-License-Identifier: Apache-2.0
//
// lwIP configuration for SchOS.
//
// The shape of this file is one decision: NO_SYS=1.
//
// lwIP can run either as a set of threads of its own (NO_SYS=0), which needs a
// port layer of semaphores, mailboxes and thread creation and then hands you a
// blocking sockets API for free; or bare, with no threading assumptions
// (NO_SYS=1), where every call must come from one context and the blocking is
// yours to write. This kernel takes the second, for two reasons: the sys_arch
// a threaded lwIP wants is more code than the socket layer it would save, and
// the kernel already has a socket layer with its own shape (kernel/net/unix.c)
// that AF_INET has to fit into rather than replace.
//
// "One context" is enforced by a single lock rather than by literally one
// thread: kernel/net/net.c takes it around the network thread's work, and the
// socket syscalls take it around theirs. That is the entire concurrency model.
#ifndef LWIP_LWIPOPTS_H
#define LWIP_LWIPOPTS_H

#define NO_SYS                      1
#define SYS_LIGHTWEIGHT_PROT        1
#define LWIP_NETCONN                0   // needs NO_SYS=0
#define LWIP_SOCKET                 0   // ours lives in kernel/net/inet.c

// Memory. All of it is static: the kernel's allocator hands out whole pages
// and nothing else, so lwIP's own pools are a better fit than wrapping kalloc.
// These numbers are sized for a handful of connections, not for a server.
#define MEM_LIBC_MALLOC             0
#define MEMP_MEM_MALLOC             0
#define MEM_ALIGNMENT               4
#define MEM_SIZE                    (192 * 1024)
#define MEMP_NUM_PBUF               32
#define MEMP_NUM_UDP_PCB            8
#define MEMP_NUM_TCP_PCB            16
#define MEMP_NUM_TCP_PCB_LISTEN     8
#define MEMP_NUM_TCP_SEG            64
#define MEMP_NUM_ARP_QUEUE          16
#define MEMP_NUM_SYS_TIMEOUT        16
#define PBUF_POOL_SIZE              48
#define PBUF_POOL_BUFSIZE           1536   // one Ethernet frame plus room

// Protocols. IPv4 only: the driver is proven for it, the QEMU test network is
// v4, and every line of v6 here would be untested.
#define LWIP_IPV4                   1
#define LWIP_IPV6                   0
#define LWIP_ARP                    1
#define LWIP_ETHERNET               1
#define LWIP_ICMP                   1
#define LWIP_RAW                    1
#define LWIP_UDP                    1
#define LWIP_TCP                    1
#define LWIP_DHCP                   1
#define LWIP_DNS                    1
#define LWIP_AUTOIP                 0
#define LWIP_IGMP                   0
#define LWIP_NETIF_HOSTNAME         1

// DHCP needs UDP checksums and a broadcast path; both are on. Requesting an
// address rather than hard-coding one matters because QEMU's user-mode network
// hands out 10.0.2.15 through DHCP and nothing else will route.
#define LWIP_NETIF_STATUS_CALLBACK  1
#define LWIP_NETIF_LINK_CALLBACK    1

#define TCP_MSS                     1460
#define TCP_SND_BUF                 (8 * TCP_MSS)
#define TCP_WND                     (8 * TCP_MSS)
#define TCP_SND_QUEUELEN            ((4 * TCP_SND_BUF) / TCP_MSS)
#define TCP_LISTEN_BACKLOG          1

// Checksums in software. The e1000 can offload them, but the driver does not
// ask it to, and a checksum computed by a device the stack has not been told
// about is the sort of mismatch that shows up only against a real peer.
#define CHECKSUM_GEN_IP             1
#define CHECKSUM_GEN_UDP            1
#define CHECKSUM_GEN_TCP            1
#define CHECKSUM_CHECK_IP           1
#define CHECKSUM_CHECK_UDP          1
#define CHECKSUM_CHECK_TCP          1

// Statistics are what /proc/net reports; they cost a few counters.
#define LWIP_STATS                  1
#define LWIP_STATS_DISPLAY          0

// Debug output off by default -- turning LWIP_DEBUG on here makes the stack
// extremely chatty on the console, which is occasionally exactly what you want.
#define LWIP_DEBUG                  0

// lwIP would otherwise provide its own errno, which would then disagree with
// the kernel's for every value a syscall returns.
#define LWIP_PROVIDE_ERRNO          1

#endif