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net: Make DNS lookup code testable
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@practicalswift
practicalswift committed Mar 8, 2021
1 parent a8b0892 commit c6b4bfb
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Showing 2 changed files with 76 additions and 61 deletions.
116 changes: 61 additions & 55 deletions src/netbase.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,50 @@ bool fNameLookup = DEFAULT_NAME_LOOKUP;
int g_socks5_recv_timeout = 20 * 1000;
static std::atomic<bool> interruptSocks5Recv(false);

std::vector<CNetAddr> WrappedGetAddrInfo(const std::string& name, bool allow_lookup)
{
addrinfo ai_hint{};
// We want a TCP port, which is a streaming socket type
ai_hint.ai_socktype = SOCK_STREAM;
ai_hint.ai_protocol = IPPROTO_TCP;
// We don't care which address family (IPv4 or IPv6) is returned
ai_hint.ai_family = AF_UNSPEC;
// If we allow lookups of hostnames, use the AI_ADDRCONFIG flag to only
// return addresses whose family we have an address configured for.
//
// If we don't allow lookups, then use the AI_NUMERICHOST flag for
// getaddrinfo to only decode numerical network addresses and suppress
// hostname lookups.
ai_hint.ai_flags = allow_lookup ? AI_ADDRCONFIG : AI_NUMERICHOST;

addrinfo* ai_res{nullptr};
const int n_err{getaddrinfo(name.c_str(), nullptr, &ai_hint, &ai_res)};
if (n_err != 0) {
return {};
}

// Traverse the linked list starting with ai_trav.
addrinfo* ai_trav{ai_res};
std::vector<CNetAddr> resolved_addresses;
while (ai_trav != nullptr) {
if (ai_trav->ai_family == AF_INET) {
assert(ai_trav->ai_addrlen >= sizeof(sockaddr_in));
resolved_addresses.emplace_back(reinterpret_cast<sockaddr_in*>(ai_trav->ai_addr)->sin_addr);
}
if (ai_trav->ai_family == AF_INET6) {
assert(ai_trav->ai_addrlen >= sizeof(sockaddr_in6));
const sockaddr_in6* s6{reinterpret_cast<sockaddr_in6*>(ai_trav->ai_addr)};
resolved_addresses.emplace_back(s6->sin6_addr, s6->sin6_scope_id);
}
ai_trav = ai_trav->ai_next;
}
freeaddrinfo(ai_res);

return resolved_addresses;
}

DNSLookupFn g_dns_lookup{WrappedGetAddrInfo};

enum Network ParseNetwork(const std::string& net_in) {
std::string net = ToLower(net_in);
if (net == "ipv4") return NET_IPV4;
Expand Down Expand Up @@ -87,7 +131,7 @@ std::vector<std::string> GetNetworkNames(bool append_unroutable)
return names;
}

bool static LookupIntern(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
static bool LookupIntern(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup, DNSLookupFn dns_lookup_function)
{
vIP.clear();

Expand All @@ -109,54 +153,16 @@ bool static LookupIntern(const std::string& name, std::vector<CNetAddr>& vIP, un
}
}

struct addrinfo aiHint;
memset(&aiHint, 0, sizeof(struct addrinfo));

// We want a TCP port, which is a streaming socket type
aiHint.ai_socktype = SOCK_STREAM;
aiHint.ai_protocol = IPPROTO_TCP;
// We don't care which address family (IPv4 or IPv6) is returned
aiHint.ai_family = AF_UNSPEC;
// If we allow lookups of hostnames, use the AI_ADDRCONFIG flag to only
// return addresses whose family we have an address configured for.
//
// If we don't allow lookups, then use the AI_NUMERICHOST flag for
// getaddrinfo to only decode numerical network addresses and suppress
// hostname lookups.
aiHint.ai_flags = fAllowLookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
struct addrinfo *aiRes = nullptr;
int nErr = getaddrinfo(name.c_str(), nullptr, &aiHint, &aiRes);
if (nErr)
return false;

// Traverse the linked list starting with aiTrav, add all non-internal
// IPv4,v6 addresses to vIP while respecting nMaxSolutions.
struct addrinfo *aiTrav = aiRes;
while (aiTrav != nullptr && (nMaxSolutions == 0 || vIP.size() < nMaxSolutions))
{
CNetAddr resolved;
if (aiTrav->ai_family == AF_INET)
{
assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in));
resolved = CNetAddr(((struct sockaddr_in*)(aiTrav->ai_addr))->sin_addr);
}

if (aiTrav->ai_family == AF_INET6)
{
assert(aiTrav->ai_addrlen >= sizeof(sockaddr_in6));
struct sockaddr_in6* s6 = (struct sockaddr_in6*) aiTrav->ai_addr;
resolved = CNetAddr(s6->sin6_addr, s6->sin6_scope_id);
for (const CNetAddr& resolved : dns_lookup_function(name, fAllowLookup)) {
if (nMaxSolutions > 0 && vIP.size() >= nMaxSolutions) {
break;
}
/* Never allow resolving to an internal address. Consider any such result invalid */
if (!resolved.IsInternal()) {
vIP.push_back(resolved);
}

aiTrav = aiTrav->ai_next;
}

freeaddrinfo(aiRes);

return (vIP.size() > 0);
}

Expand All @@ -175,7 +181,7 @@ bool static LookupIntern(const std::string& name, std::vector<CNetAddr>& vIP, un
* @see Lookup(const char *, std::vector<CService>&, int, bool, unsigned int)
* for additional parameter descriptions.
*/
bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup, DNSLookupFn dns_lookup_function)
{
if (!ValidAsCString(name)) {
return false;
Expand All @@ -187,7 +193,7 @@ bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned in
strHost = strHost.substr(1, strHost.size() - 2);
}

return LookupIntern(strHost, vIP, nMaxSolutions, fAllowLookup);
return LookupIntern(strHost, vIP, nMaxSolutions, fAllowLookup, dns_lookup_function);
}

/**
Expand All @@ -196,13 +202,13 @@ bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned in
* @see LookupHost(const std::string&, std::vector<CNetAddr>&, unsigned int, bool) for
* additional parameter descriptions.
*/
bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup)
bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup, DNSLookupFn dns_lookup_function)
{
if (!ValidAsCString(name)) {
return false;
}
std::vector<CNetAddr> vIP;
LookupHost(name, vIP, 1, fAllowLookup);
LookupHost(name, vIP, 1, fAllowLookup, dns_lookup_function);
if(vIP.empty())
return false;
addr = vIP.front();
Expand All @@ -229,7 +235,7 @@ bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup)
* @returns Whether or not the service string successfully resolved to any
* resulting services.
*/
bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions)
bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions, DNSLookupFn dns_lookup_function)
{
if (name.empty() || !ValidAsCString(name)) {
return false;
Expand All @@ -239,7 +245,7 @@ bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefau
SplitHostPort(name, port, hostname);

std::vector<CNetAddr> vIP;
bool fRet = LookupIntern(hostname, vIP, nMaxSolutions, fAllowLookup);
bool fRet = LookupIntern(hostname, vIP, nMaxSolutions, fAllowLookup, dns_lookup_function);
if (!fRet)
return false;
vAddr.resize(vIP.size());
Expand All @@ -254,13 +260,13 @@ bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefau
* @see Lookup(const char *, std::vector<CService>&, int, bool, unsigned int)
* for additional parameter descriptions.
*/
bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup)
bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup, DNSLookupFn dns_lookup_function)
{
if (!ValidAsCString(name)) {
return false;
}
std::vector<CService> vService;
bool fRet = Lookup(name, vService, portDefault, fAllowLookup, 1);
bool fRet = Lookup(name, vService, portDefault, fAllowLookup, 1, dns_lookup_function);
if (!fRet)
return false;
addr = vService[0];
Expand All @@ -277,15 +283,15 @@ bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllo
* @see Lookup(const char *, CService&, int, bool) for additional parameter
* descriptions.
*/
CService LookupNumeric(const std::string& name, int portDefault)
CService LookupNumeric(const std::string& name, int portDefault, DNSLookupFn dns_lookup_function)
{
if (!ValidAsCString(name)) {
return {};
}
CService addr;
// "1.2:345" will fail to resolve the ip, but will still set the port.
// If the ip fails to resolve, re-init the result.
if(!Lookup(name, addr, portDefault, false))
if(!Lookup(name, addr, portDefault, false, dns_lookup_function))
addr = CService();
return addr;
}
Expand Down Expand Up @@ -811,7 +817,7 @@ bool ConnectThroughProxy(const proxyType& proxy, const std::string& strDest, int
*
* @returns Whether the operation succeeded or not.
*/
bool LookupSubNet(const std::string& strSubnet, CSubNet& ret)
bool LookupSubNet(const std::string& strSubnet, CSubNet& ret, DNSLookupFn dns_lookup_function)
{
if (!ValidAsCString(strSubnet)) {
return false;
Expand All @@ -822,7 +828,7 @@ bool LookupSubNet(const std::string& strSubnet, CSubNet& ret)
std::string strAddress = strSubnet.substr(0, slash);
// TODO: Use LookupHost(const std::string&, CNetAddr&, bool) instead to just get
// one CNetAddr.
if (LookupHost(strAddress, vIP, 1, false))
if (LookupHost(strAddress, vIP, 1, false, dns_lookup_function))
{
CNetAddr network = vIP[0];
if (slash != strSubnet.npos)
Expand All @@ -837,7 +843,7 @@ bool LookupSubNet(const std::string& strSubnet, CSubNet& ret)
else // If not a valid number, try full netmask syntax
{
// Never allow lookup for netmask
if (LookupHost(strNetmask, vIP, 1, false)) {
if (LookupHost(strNetmask, vIP, 1, false, dns_lookup_function)) {
ret = CSubNet(network, vIP[0]);
return ret.IsValid();
}
Expand Down
21 changes: 15 additions & 6 deletions src/netbase.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,11 @@ struct ProxyCredentials
std::string password;
};

/**
* Wrapper for getaddrinfo(3). Do not use directly: call Lookup/LookupHost/LookupNumeric/LookupSubNet.
*/
std::vector<CNetAddr> WrappedGetAddrInfo(const std::string& name, bool allow_lookup);

enum Network ParseNetwork(const std::string& net);
std::string GetNetworkName(enum Network net);
/** Return a vector of publicly routable Network names; optionally append NET_UNROUTABLE. */
Expand All @@ -74,12 +79,16 @@ bool IsProxy(const CNetAddr &addr);
bool SetNameProxy(const proxyType &addrProxy);
bool HaveNameProxy();
bool GetNameProxy(proxyType &nameProxyOut);
bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup);
bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup);
bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup);
bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);
CService LookupNumeric(const std::string& name, int portDefault = 0);
bool LookupSubNet(const std::string& strSubnet, CSubNet& subnet);

using DNSLookupFn = std::function<std::vector<CNetAddr>(const std::string&, bool)>;
extern DNSLookupFn g_dns_lookup;

bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup, DNSLookupFn dns_lookup_function = g_dns_lookup);
bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions, DNSLookupFn dns_lookup_function = g_dns_lookup);
CService LookupNumeric(const std::string& name, int portDefault = 0, DNSLookupFn dns_lookup_function = g_dns_lookup);
bool LookupSubNet(const std::string& strSubnet, CSubNet& subnet, DNSLookupFn dns_lookup_function = g_dns_lookup);

/**
* Create a TCP socket in the given address family.
Expand Down

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