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finish (halfassed) DNS support.

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This commit is contained in:
Arisotura 2019-03-05 13:24:42 +01:00
parent a88f0b6792
commit 950170df6d
1 changed files with 150 additions and 6 deletions
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156
src/libui_sdl/LAN_Socket.cpp
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@ -380,6 +380,9 @@ void HandleDNSFrame(u8* data, int len)
u8* udpheader = &data[0x22];
u8* dnsbody = &data[0x2A];
u32 srcip = ntohl(*(u32*)&ipheader[12]);
u16 srcport = ntohs(*(u16*)&udpheader[0]);
u16 id = ntohs(*(u16*)&dnsbody[0]);
u16 flags = ntohs(*(u16*)&dnsbody[2]);
u16 numquestions = ntohs(*(u16*)&dnsbody[4]);
@ -390,33 +393,174 @@ void HandleDNSFrame(u8* data, int len)
printf("DNS: ID=%04X, flags=%04X, Q=%d, A=%d, auth=%d, add=%d\n",
id, flags, numquestions, numanswers, numauth, numadd);
// for now we only take 'simple' DNS requests
if (flags & 0x8000) return;
if (numquestions != 1 || numanswers != 0) return;
u8 resp[1024];
u8* out = &resp[0];
// ethernet
memcpy(out, &data[6], 6); out += 6;
memcpy(out, kServerMAC, 6); out += 6;
*(u16*)out = htons(0x0800); out += 2;
// IP
u8* resp_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(kDNSIP); out += 4; // source IP
*(u32*)out = htonl(srcip); out += 4; // destination IP
// UDP
u8* resp_udpheader = out;
*(u16*)out = htons(53); out += 2; // source port
*(u16*)out = htons(srcport); out += 2; // destination port
*(u16*)out = 0; out += 2; // length
*(u16*)out = 0; out += 2; // checksum
// DNS
u8* resp_body = out;
*(u16*)out = htons(id); out += 2; // ID
*(u16*)out = htons(0x8000); out += 2; // flags
*(u16*)out = htons(numquestions); out += 2; // num questions
*(u16*)out = htons(numquestions); out += 2; // num answers
*(u16*)out = 0; out += 2; // num authority
*(u16*)out = 0; out += 2; // num additional
u32 curoffset = 12;
for (u16 i = 0; i < numquestions; i++)
{
if (curoffset >= (len-0x2A)) return;
u8 bitlength = 0;
while ((bitlength = dnsbody[curoffset++]) != 0)
curoffset += bitlength;
curoffset += 4;
}
u32 qlen = curoffset-12;
if (qlen > 512) return;
memcpy(out, &dnsbody[12], qlen); out += qlen;
curoffset = 12;
for (u16 i = 0; i < numquestions; i++)
{
// Assemble the requested domain name
// assemble the requested domain name
u8 bitlength = 0;
char domainname[256] = ""; int o = 0;
while ((bitlength = dnsbody[curoffset++]) != 0)
{
if ((o+bitlength) >= 255) break;
if ((o+bitlength) >= 255)
{
// welp. atleast try not to explode.
domainname[o++] = '\0';
break;
}
strncpy(&domainname[o], (const char *)&dnsbody[curoffset], bitlength);
o += bitlength;
curoffset += bitlength;
if (dnsbody[curoffset] != 0)
{
domainname[o++] = '.';
}
else
domainname[o++] = '\0';
}
printf("- q%d: %s", i, domainname);
u16 type = ntohs(*(u16*)&dnsbody[curoffset]);
u16 cls = ntohs(*(u16*)&dnsbody[curoffset+2]);
// TODO: get answer
printf("- q%d: %04X %04X %s", i, type, cls, domainname);
// get answer
struct addrinfo dns_hint;
struct addrinfo* dns_res;
u32 addr_res;
memset(&dns_hint, 0, sizeof(dns_hint));
dns_hint.ai_family = AF_INET; // TODO: other address types (INET6, etc)
if (getaddrinfo(domainname, "0", &dns_hint, &dns_res) == 0)
{
struct addrinfo* p = dns_res;
while (p)
{
struct sockaddr_in* addr = (struct sockaddr_in*)p->ai_addr;
printf(" -> %d.%d.%d.%d",
addr->sin_addr.S_un.S_un_b.s_b1, addr->sin_addr.S_un.S_un_b.s_b2,
addr->sin_addr.S_un.S_un_b.s_b3, addr->sin_addr.S_un.S_un_b.s_b4);
addr_res = addr->sin_addr.S_un.S_addr;
p = p->ai_next;
}
}
else
{
printf(" shat itself :(");
addr_res = 0;
}
printf("\n");
curoffset += 4;
// TODO: betterer support
// (under which conditions does the C00C marker work?)
*(u16*)out = htons(0xC00C); out += 2;
*(u16*)out = htons(type); out += 2;
*(u16*)out = htons(cls); out += 2;
*(u32*)out = htonl(3600); out += 4; // TTL (hardcoded for now)
*(u16*)out = htons(4); out += 2; // address length
*(u32*)out = addr_res; out += 4; // address
}
// lengths
u32 framelen = (u32)(out - &resp[0]);
if (framelen & 1) { *out++ = 0; framelen++; }
*(u16*)&resp_ipheader[2] = htons(framelen - 0xE);
*(u16*)&resp_udpheader[4] = htons(framelen - (0xE + 0x14));
// IP checksum
u32 tmp = 0;
for (int i = 0; i < 20; i += 2)
tmp += ntohs(*(u16*)&resp_ipheader[i]);
while (tmp >> 16)
tmp = (tmp & 0xFFFF) + (tmp >> 16);
tmp ^= 0xFFFF;
*(u16*)&resp_ipheader[10] = htons(tmp);
// UDP checksum
// (note: normally not mandatory, but some older sgIP versions require it)
tmp = 0;
tmp += ntohs(*(u16*)&resp_ipheader[12]);
tmp += ntohs(*(u16*)&resp_ipheader[14]);
tmp += ntohs(*(u16*)&resp_ipheader[16]);
tmp += ntohs(*(u16*)&resp_ipheader[18]);
tmp += ntohs(0x1100);
tmp += (u32)(out - resp_udpheader);
for (u8* i = resp_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*)&resp_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
PacketLen = framelen;
memcpy(PacketBuffer, resp, PacketLen);
RXNum = 1;
}
void HandleIPFrame(u8* data, int len)