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start work on non-direct mode. reply to DHCP discover frame.

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This commit is contained in:
Arisotura
2019-02-23 13:41:51 +01:00
parent 0550d22833
commit 93d51b0cbc
4 changed files with 206 additions and 9 deletions
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184
src/libui_sdl/LAN.cpp
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@ -77,7 +77,9 @@ pcap_t* PCapAdapter = NULL;
u8 PCapPacketBuffer[2048];
int PCapPacketLen;
int PCapRXNum;
volatile int PCapRXNum;
u16 IPv4ID;
#define LOAD_PCAP_FUNC(sym) \
@ -107,6 +109,8 @@ bool Init()
PCapPacketLen = 0;
PCapRXNum = 0;
IPv4ID = 1;
for (int i = 0; PCapLibNames[i]; i++)
{
void* lib = SDL_LoadObject(PCapLibNames[i]);
@ -296,6 +300,179 @@ void RXCallback(u_char* blarg, const struct pcap_pkthdr* header, const u_char* d
memcpy(PCapPacketBuffer, data, PCapPacketLen);
PCapRXNum = 1;
}
u32 zarp=0;
bool HandleDHCPFrame(u8* data, int len)
{
const u32 serverip = 0x0A404001;
const u32 clientip = 0x0A404010;
u8 type = 0xFF;
u32 transid = *(u32*)&data[0x2E];
zarp=transid;
u8* options = &data[0x11A];
for (;;)
{
if (options >= &data[len]) break;
u8 opt = *options++;
if (opt == 255) break;
u8 len = *options++;
switch (opt)
{
case 53: // frame type
type = options[0];
break;
}
options += len;
}
if (type == 0xFF)
{
printf("DHCP: bad frame\n");
return false;
}
printf("DHCP: frame type %d, transid %08X\n", type, transid);
if (type == 1) // discover
{
u8 resp[512];
u8* out = &resp[0];
// ethernet
memcpy(out, &data[6], 6); out += 6;
*out++ = 0x00; *out++ = 0xAB; *out++ = 0x33;
*out++ = 0x28; *out++ = 0x99; *out++ = 0x44;
*(u16*)out = htons(0x0800); out += 2;
// IP
u8* ipheader = out;
*out++ = 0x45;
*out++ = 0x00;
*(u16*)out = 0; out += 2; // total length
*(u16*)out = htons(IPv4ID); out += 2; IPv4ID++;
*out++ = 0x00;
*out++ = 0x00;
*out++ = 0x80; // TTL
*out++ = 0x11; // protocol (UDP)
*(u16*)out = 0; out += 2; // checksum
*(u32*)out = htonl(serverip); out += 4; // source IP
*(u32*)out = htonl(0xFFFFFFFF); out += 4; // destination IP
// UDP
u8* udpheader = out;
*(u16*)out = htons(67); out += 2; // source port
*(u16*)out = htons(68); out += 2; // destination port
*(u16*)out = 0; out += 2; // length
*(u16*)out = 0; out += 2; // checksum
// DHCP
u8* body = out;
*out++ = 0x02;
*out++ = 0x01;
*out++ = 0x06;
*out++ = 0x00;
*(u32*)out = transid; out += 4;
*(u16*)out = 0; out += 2; // seconds elapsed
*(u16*)out = 0; out += 2;
*(u32*)out = htonl(0x00000000); out += 4; // client IP
*(u32*)out = htonl(clientip); out += 4; // your IP
*(u32*)out = htonl(serverip); out += 4; // server IP
*(u32*)out = htonl(0x00000000); out += 4; // gateway IP
memcpy(out, &data[6], 6); out += 6;
memset(out, 0, 10); out += 10;
memset(out, 0, 192); out += 192;
*(u32*)out = 0x63538263; out += 4; // DHCP magic
// DHCP options
*out++ = 53; *out++ = 1;
*out++ = 2; // DHCP type: offer
*out++ = 1; *out++ = 4;
*(u32*)out = htonl(0xFFFFFF00); out += 4; // subnet mask
*out++ = 3; *out++ = 4;
*(u32*)out = htonl(serverip); out += 4; // router
*out++ = 51; *out++ = 4;
*(u32*)out = htonl(442030); out += 4; // lease time
*out++ = 54; *out++ = 4;
*(u32*)out = htonl(serverip); out += 4; // DHCP server
*out++ = 6; *out++ = 4;
*(u32*)out = htonl(0x08080808); out += 4; // DNS (TODO!!)
*out++ = 0xFF;
memset(out, 0, 20); out += 20;
// lengths
u32 framelen = (u32)(out - &resp[0]);
if (framelen & 1) { *out++ = 0; framelen++; }
*(u16*)&ipheader[2] = htons(framelen - 0xE);
*(u16*)&udpheader[4] = htons(framelen - (0xE + 0x14));
// IP checksum
u32 tmp = 0;
for (int i = 0; i < 20; i += 2)
tmp += ntohs(*(u16*)&ipheader[i]);
while (tmp >> 16)
tmp = (tmp & 0xFFFF) + (tmp >> 16);
tmp ^= 0xFFFF;
*(u16*)&ipheader[10] = htons(tmp);
// UDP checksum
// (note: normally not mandatory, but some older sgIP versions require it)
tmp = 0;
tmp += ntohs(*(u16*)&ipheader[12]);
tmp += ntohs(*(u16*)&ipheader[14]);
tmp += ntohs(*(u16*)&ipheader[16]);
tmp += ntohs(*(u16*)&ipheader[18]);
tmp += ntohs(0x1100);
tmp += (u32)(out - udpheader);
for (u8* i = udpheader; i < out; i += 2)
tmp += ntohs(*(u16*)i);
while (tmp >> 16)
tmp = (tmp & 0xFFFF) + (tmp >> 16);
tmp ^= 0xFFFF;
if (tmp == 0) tmp = 0xFFFF;
*(u16*)&udpheader[6] = htons(tmp);
// TODO: if there is already a packet queued, this will overwrite it
// that being said, this will only happen during DHCP setup, so probably
// not a big deal
PCapPacketLen = framelen;
memcpy(PCapPacketBuffer, resp, PCapPacketLen);
PCapRXNum = 1;
// DEBUG!!
//pcap_sendpacket(PCapAdapter, data, len);
//pcap_sendpacket(PCapAdapter, resp, framelen);
return true;
}
return false;
}
bool HandlePacket(u8* data, int len)
{
if (ntohs(*(u16*)&data[0xC]) != 0x0800) // IPv4
return false;
u8 protocol = data[0x17];
if (protocol == 0x11) // UDP
{
u16 srcport = ntohs(*(u16*)&data[0x22]);
u16 dstport = ntohs(*(u16*)&data[0x24]);
if (srcport == 68 && dstport == 67) // DHCP
{
printf("LANMAGIC: DHCP packet\n");
return HandleDHCPFrame(data, len);
}
}
return false;
}
int SendPacket(u8* data, int len)
{
@ -310,7 +487,8 @@ int SendPacket(u8* data, int len)
if (!Config::DirectLAN)
{
// TODO!
if (HandlePacket(data, len))
return len;
}
pcap_sendpacket(PCapAdapter, data, len);
@ -331,7 +509,7 @@ int RecvPacket(u8* data)
PCapRXNum = 0;
}
pcap_dispatch(PCapAdapter, 1, RXCallback, NULL);
//pcap_dispatch(PCapAdapter, 1, RXCallback, NULL);
return ret;
}