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Fix ip & tcp header calculation in memcache command #20

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Fix ip & tcp header calculation in memcache command #20

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25 changes: 12 additions & 13 deletions src/net/memcache_command.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,14 +27,6 @@ using namespace std;
MemcacheCommand MemcacheCommand::create(const Packet& pkt,
const bpf_u_int32 captureAddress)
{
static ssize_t ether_header_sz = sizeof(struct ether_header);
static ssize_t ip_sz = sizeof(struct ip);
static ssize_t tcphdr_sz = sizeof(struct tcphdr);

const struct ether_header* ethernetHeader;
const struct ip* ipHeader;
const struct tcphdr* tcpHeader;

const Packet::Header* pkthdr = &pkt.getHeader();
const Packet::Data* packet = pkt.getData();

Expand All @@ -46,14 +38,16 @@ MemcacheCommand MemcacheCommand::create(const Packet& pkt,

// must be an IP packet
// TODO add support for dumping localhost
ethernetHeader = (struct ether_header*)packet;
const struct ether_header* ethernetHeader = (struct ether_header*)packet;
ssize_t ethernetHeaderSize = sizeof(struct ether_header); //14 bytes
auto etype = ntohs(ethernetHeader->ether_type);
if (etype != ETHERTYPE_IP) {
return MemcacheCommand();
}

// must be TCP - TODO add support for UDP
ipHeader = (struct ip*)(packet + ether_header_sz);
const struct ip* ipHeader = (struct ip*)(packet + ethernetHeaderSize);
ssize_t ipHeaderSize = ipHeader->ip_hl * 4;
auto itype = ipHeader->ip_p;
if (itype != IPPROTO_TCP) {
return MemcacheCommand();
Expand All @@ -69,15 +63,20 @@ MemcacheCommand MemcacheCommand::create(const Packet& pkt,
// FIXME will remove once we add back the direction parsing
(void)possible_request;

tcpHeader = (struct tcphdr*)(packet + ether_header_sz + ip_sz);
const struct tcphdr* tcpHeader = (struct tcphdr*)(packet + ethernetHeaderSize
+ ipHeaderSize);
ssize_t tcpHeaderSize = tcpHeader->doff * 4;
(void)tcpHeader;
data = (u_char*)(packet + ether_header_sz + ip_sz + tcphdr_sz);
dataLength = pkthdr->len - (ether_header_sz + ip_sz + tcphdr_sz);
data = (u_char*)(packet + ethernetHeaderSize + ipHeaderSize + tcpHeaderSize);
dataLength = pkthdr->len - (ethernetHeaderSize + ipHeaderSize + tcpHeaderSize);
if (dataLength > pkthdr->caplen) {
dataLength = pkthdr->caplen;
}

// TODO revert to detecting request/response and doing the right thing
if (dataLength <= 0) {
return MemcacheCommand();
}
return MemcacheCommand::makeResponse(data, dataLength, sourceAddress);
}

Expand Down