diff options
Diffstat (limited to 'src/user/app/netstack/tcp.c')
| -rw-r--r-- | src/user/app/netstack/tcp.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/src/user/app/netstack/tcp.c b/src/user/app/netstack/tcp.c new file mode 100644 index 0000000..71e82f2 --- /dev/null +++ b/src/user/app/netstack/tcp.c @@ -0,0 +1,180 @@ +/* Welcome to spaghetti land. */ +#include "proto.h" +#include "util.h" + +enum { + SrcPort = 0, + DstPort = 2, + Seq = 4, + AckNum = 8, /* last processed seq + 1 */ + Flags = 12, + FlagSize = 0xF000, /* size of header / 4 bytes */ + /* 3 bits: 0, still unused + * 3 bits: modern stuff not in the original RFC */ + FlagURG = 0x0020, /* urgent */ + FlagACK = 0x0010, + FlagPSH = 0x0008, /* force buffer flush */ + FlagRST = 0x0004, /* reset connection */ + FlagSYN = 0x0002, /* first packet; sync sequence numbers */ + FlagFIN = 0x0001, /* last packet */ + FlagAll = 0x003F, + WinSize = 14, /* amount of data we're willing to receive */ + Checksum = 16, + Urgent = 18, + MinHdr = 20, +}; + +enum tcp_state { + LISTEN, + SYN_RCVD, + LAST_ACK, + CLOSED, +}; + +struct tcp_conn { + uint32_t lip, rip; + mac_t rmac; + uint16_t lport, rport; + struct tcp_conn *next, **link; + + enum tcp_state state; + uint32_t lack, rack; + uint32_t lseq; + bool uclosed; /* did the user close? */ + + void (*on_conn)(struct tcp_conn *, void *carg); + void (*on_close)(void *carg); + void *carg; +}; +static struct tcp_conn *conns; +static void conns_append(struct tcp_conn *c) { + c->next = conns; + if (c->next) + c->next->link = &c->next; + c->link = &conns; + *c->link = c; +} +static void tcpc_send(struct tcp_conn *c, uint16_t flags) { + uint8_t *pkt = malloc(MinHdr); + memset(pkt, 0, MinHdr); + + nput16(pkt + SrcPort, c->lport); + nput16(pkt + DstPort, c->rport); + nput32(pkt + Seq, c->lseq); + nput32(pkt + AckNum, c->lack); + flags |= (MinHdr / 4) << 12; + nput16(pkt + Flags, flags); + nput16(pkt + WinSize, 4096); + nput16(pkt + Checksum, ip_checksumphdr(pkt, MinHdr, c->lip, c->rip, 6)); + + ipv4_send(pkt, MinHdr, (struct ipv4){ + .proto = 6, + .src = c->lip, + .dst = c->rip, + .e.dst = &c->rmac, + }); + free(pkt); +} +void tcp_listen( + uint16_t port, + void (*on_conn)(struct tcp_conn *, void *carg), + void (*on_close)(void *carg), + void *carg) +{ + struct tcp_conn *c = malloc(sizeof *c); + c->lport = port; + c->lip = state.ip; + c->state = LISTEN; + c->on_conn = on_conn; + c->on_close = on_close; + c->carg = carg; + conns_append(c); +} +void tcpc_close(struct tcp_conn *c) { + /* ONLY FOR USE BY THE USER, drops their reference */ + if (!c->uclosed) { + c->uclosed = true; + tcpc_send(c, FlagFIN | FlagACK); + c->state = LAST_ACK; + c->on_conn = NULL; + c->on_close = NULL; + } +} + +void tcp_parse(const uint8_t *buf, size_t len, struct ipv4 ip) { + if (len < 20) return; + uint16_t srcport = nget16(buf + SrcPort); + uint16_t dstport = nget16(buf + DstPort); + uint32_t seq = nget32(buf + Seq); + uint32_t acknum = nget32(buf + AckNum); + uint16_t flags = nget16(buf + Flags); + uint16_t winsize = nget16(buf + WinSize); + uint16_t chksum = nget16(buf + Checksum); + uint16_t hdrlen = ((flags & FlagSize) >> 12) * 4; + if (hdrlen > len) return; + uint16_t payloadlen = len - hdrlen; + + for (struct tcp_conn *iter = conns; iter; iter = iter->next) { + if (iter->state == CLOSED) continue; + if (iter->lport != dstport) continue; + + if (iter->state == LISTEN && (flags & FlagAll) == FlagSYN) { + iter->state = SYN_RCVD; + iter->rip = ip.src; + iter->rport = srcport; + iter->lack = seq + 1; + memcpy(&iter->rmac, ip.e.src, sizeof(mac_t)); + tcpc_send(iter, FlagSYN | FlagACK); + iter->lseq++; + if (iter->on_conn) iter->on_conn(iter, iter->carg); + return; + } + + if (iter->rip == ip.src && iter->rport == srcport) { + // TODO doesn't handle seq/ack overflows + if (flags & FlagACK) { + if (iter->rack < acknum) + iter->rack = acknum; + if (iter->state == LAST_ACK) { + iter->state = CLOSED; // TODO check if ack has correct number + // TODO free (also after a timeout) + return; + } + } + if (iter->lack != seq && iter->lack - 1 != seq) { + eprintf("remote seq jumped by %d", seq - iter->lack); + tcpc_send(iter, FlagACK); + return; + } + iter->lack = seq + 1; + if (flags & FlagFIN) { + // TODO should resend the packet until an ACK is received + // TODO duplicated in tcpc_close + tcpc_send(iter, FlagFIN | FlagACK); + iter->state = LAST_ACK; + if (iter->on_close) iter->on_close(iter->carg); + return; + } + return; + } + } + + uint8_t *pkt = malloc(MinHdr); + memset(pkt, 0, MinHdr); + nput16(pkt + SrcPort, dstport); + nput16(pkt + DstPort, srcport); + nput32(pkt + Seq, acknum); + nput32(pkt + AckNum, seq + 1); + uint16_t pktflags = FlagRST | FlagACK; + pktflags |= (MinHdr / 4) << 12; + nput16(pkt + Flags, pktflags); + nput16(pkt + Checksum, ip_checksumphdr(pkt, MinHdr, ip.src, ip.dst, 6)); + + ipv4_send(pkt, MinHdr, (struct ipv4){ + .proto = 6, + .src = ip.dst, + .dst = ip.src, + .e.dst = ip.e.src, + }); + free(pkt); +} |