softwarecontainer::Netlink Class Reference

Handles various network operations over netlink. More...

#include <netlink.h>

Public Types
typedef std::pair< rtattr, void * >	AttributeInfo
typedef std::vector< AttributeInfo >	AttributeList
typedef std::pair< ifinfomsg, AttributeList >	LinkInfo
typedef std::pair< ifaddrmsg, AttributeList >	AddressInfo
typedef std::pair< rtmsg, AttributeList >	RouteInfo

Public Member Functions
	LOG_DECLARE_CLASS_CONTEXT ("NETL","Netlink")
	Netlink ()
	Construct a new Netlink object. More...
virtual	~Netlink ()
	release all resources held by the Netlink object More...
bool	getKernelDump ()
	get a dump of all links, addresses and routes from the kernel. More...
virtual bool	checkKernelDump ()
	check for a kernel dump, and if not present, try to get one More...
bool	setDefaultGateway (const char *gatewayAddress)
	Sets an ip address as the default gateway. More...
bool	linkUp (const int ifaceIndex)
	Bring the given interface up. More...
bool	linkDown (const int ifaceIndex)
	Bring a given interface down. More...
bool	setIP (const int ifaceIndex, const in_addr ip, const unsigned char netmask)
	Sets an IP address for a network link. More...
bool	findLink (const char *ifaceName, LinkInfo &linkInfo)
	Check that the device given is a network bridge. More...
bool	findAddresses (const unsigned int interfaceIndex, std::vector< AddressInfo > &result)
	Get all addresses associated with the given interface index. More...
bool	hasAddress (const std::vector< AddressInfo > &haystack, const int addressFamily, const char *needle)
	checks if an address is present in the given list More...

Detailed Description

Handles various network operations over netlink.

Some of the code in this class is based on code shown here, written by Jean Lorchat http://iijean.blogspot.se/2010/03/howto-get-list-of-network-interfaces-in.html

Definition at line 37 of file netlink.h.

Constructor & Destructor Documentation

softwarecontainer::Netlink::Netlink

(

)

Construct a new Netlink object.

This will do a setup of the sockets needed to talk netlink to the kernel, and will also call getKernelDump()

Definition at line 30 of file netlink.cpp.

References getKernelDump().

{
    m_sequenceNumber = 1;
    m_hasKernelDump = false;
    m_netlinkInitialized = false;

    if (!setupNetlink()) {
        fprintf(stderr, "Failed to setup netlink\n");
    }

    if (!getKernelDump()) {
        fprintf(stderr, "Failed to initialize cache\n");
    }
}

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softwarecontainer::Netlink::~Netlink ( )

virtual

release all resources held by the Netlink object

Since we allocate everything on the stack, except for the netlink attributes which we save as void pointers, we basically go through all data structures and free those pointers.

Also shuts down the communication with the kernel.

Definition at line 45 of file netlink.cpp.

{
    if (m_netlinkInitialized) {
        shutdown(m_fd, SHUT_RDWR);
        close(m_fd);
    }

    if (m_hasKernelDump) {
        clearCache();
    }
}

Member Function Documentation

bool softwarecontainer::Netlink::getKernelDump

(

)

get a dump of all links, addresses and routes from the kernel.

To get a dump of all links/addresses/routes we only need to use the generic netlink family message type, and for that we only need to set family (AF_PACKET).

This is done by sending RTM_GETLINK, RTM_GETADDR and RTM_GETROUTE as a general message (rtgenmsg) to the kernel.

After running this successfully, there will be a local cache of these network objects, which is needed to run some of the other functions.

Returns

true on success, false otherwise

See also

clearCache()

Definition at line 458 of file netlink.cpp.

Referenced by checkKernelDump(), and Netlink().

{
    m_hasKernelDump = false;

    netlink_request<rtgenmsg> link_msg = createMessage<rtgenmsg>(RTM_GETLINK, NLM_F_DUMP);
    link_msg.pay.rtgen_family = AF_PACKET;
    if (!sendMessage(link_msg)) {
        std::cerr << "Could not send link message" << std::endl;
        return false;
    }

    netlink_request<rtgenmsg> addr_msg = createMessage<rtgenmsg>(RTM_GETADDR, NLM_F_DUMP);
    addr_msg.pay.rtgen_family = AF_PACKET;
    if (!sendMessage(addr_msg)) {
        std::cerr << "Could not send address message" << std::endl;
        return false;
    }

    netlink_request<rtgenmsg> route_msg = createMessage<rtgenmsg>(RTM_GETROUTE, NLM_F_DUMP);
    route_msg.pay.rtgen_family = AF_PACKET;
    if (!sendMessage(route_msg)) {
        std::cerr << "Could not send route message" << std::endl;
        return false;
    }

    m_hasKernelDump = true;
    return true;
}

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bool softwarecontainer::Netlink::checkKernelDump ( )

virtual

check for a kernel dump, and if not present, try to get one

Returns

true if there a kernel dump was found or could be fetched

false otherwise

Definition at line 487 of file netlink.cpp.

References getKernelDump().

Referenced by findAddresses(), findLink(), and linkUp().

{
    if (!m_hasKernelDump && !getKernelDump()) {
        std::cerr << "Could not get cache dump from kernel" << std::endl;
        return false;
    }

    return true;
}

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bool softwarecontainer::Netlink::setDefaultGateway

(

const char *

gatewayAddress

)

Sets an ip address as the default gateway.

Parameters

gatewayAddress

the address to set

Returns

true on success

false otherwise

Definition at line 175 of file netlink.cpp.

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    netlink_request<rtmsg> set_gw = createMessage<rtmsg>(RTM_NEWROUTE, NLM_F_CREATE | NLM_F_REPLACE);
    set_gw.pay.rtm_family = AF_INET;
    set_gw.pay.rtm_table = RT_TABLE_MAIN;
    set_gw.pay.rtm_protocol = RTPROT_STATIC;
    set_gw.pay.rtm_scope = RT_SCOPE_UNIVERSE;
    set_gw.pay.rtm_type = RTN_UNICAST;

    struct in_addr gw_addr;
    if (inet_aton(gatewayAddress, &gw_addr) == 0) {
        return false;
    }
    addAttribute(set_gw, RTA_GATEWAY, sizeof(gw_addr), &gw_addr);

    return sendMessage(set_gw);
}

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bool softwarecontainer::Netlink::linkUp

(

const int

ifaceIndex

)

Bring the given interface up.

Sets the UP flag for the given interface, if it exists.

Parameters

ifaceIndex

the index for the interface to bring up

Returns

true if the interface was found and brought up

false otherwise

Definition at line 194 of file netlink.cpp.

References checkKernelDump().

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    if (!checkKernelDump()) {
        return false;
    }

    for (LinkInfo link : m_links) {
        ifinfomsg ifinfo = link.first;
        if (ifinfo.ifi_index != ifaceIndex) {
            continue;
        }

        // First, bring the link up
        netlink_request<ifinfomsg> msg_up = createMessage<ifinfomsg>(RTM_NEWLINK, NLM_F_CREATE);
        msg_up.pay.ifi_family = AF_UNSPEC;
        msg_up.pay.ifi_flags = ifinfo.ifi_flags | IFF_UP;
        msg_up.pay.ifi_change |= IFF_UP;
        msg_up.pay.ifi_index = ifinfo.ifi_index;
        if (!sendMessage(msg_up)) {
            fprintf(stderr, "Failed to bring device %i up\n", ifinfo.ifi_index);
            return false;
        } else {
            return true;
        }
    }

    return false;
}

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bool softwarecontainer::Netlink::linkDown

(

const int

ifaceIndex

)

Bring a given interface down.

Parameters

ifaceIndex

the index for the interface to bring down

Returns

true if interface was found and brought down

false otherwise

Definition at line 261 of file netlink.cpp.

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    for (LinkInfo link : m_links) {
        ifinfomsg ifinfo = link.first;
        if (ifinfo.ifi_type == ARPHRD_LOOPBACK) {
            continue; // This is the loopback device
        }

        if (ifinfo.ifi_index != ifaceIndex) {
            continue; // Only bring down the requested iface
        }

        netlink_request<ifinfomsg> down_msg = createMessage<ifinfomsg>(RTM_NEWLINK, 0);
        down_msg.pay.ifi_family = AF_UNSPEC;
        down_msg.pay.ifi_index = ifinfo.ifi_index;
        down_msg.pay.ifi_flags = ~IFF_UP;
        down_msg.pay.ifi_change = IFF_UP;

        if (!sendMessage(down_msg)) {
            return false;
        } else {
            return true;
        }
    }

    return false;
}

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bool softwarecontainer::Netlink::setIP	(	const int	ifaceIndex,
		const in_addr	ip,
		const unsigned char	netmask
	)

Sets an IP address for a network link.

Parameters

ifaceIndex	the index for the interface to set ip for
ip	the ipv4 address to set
netmask	the netmask in CIDR format (for example 24)

Returns

true if interface was found and IP was set

false otherwise

Definition at line 223 of file netlink.cpp.

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    for (LinkInfo link : m_links) {
        ifinfomsg ifinfo = link.first;
        if (ifinfo.ifi_index != ifaceIndex) {
            continue;
        }

        // TODO: Support for ipv6
        netlink_request<ifaddrmsg> msg_setip = createMessage<ifaddrmsg>(RTM_NEWADDR, NLM_F_CREATE | NLM_F_REPLACE);
        msg_setip.pay.ifa_family = AF_INET; // ipv4
        msg_setip.pay.ifa_prefixlen = netmask;
        msg_setip.pay.ifa_scope = RT_SCOPE_UNIVERSE;
        msg_setip.pay.ifa_index = ifinfo.ifi_index; // interface (link)

        // Calculate the broadcast address.
        // Broadcast = IP | (~Netmask)
        in_addr_t inet_netmask = (1 << netmask) -1;
        in_addr_t inet_bcast = ip.s_addr | (~inet_netmask);
        in_addr bcast_addr = { inet_bcast };

        addAttribute(msg_setip, IFA_LOCAL, sizeof(ip), &ip);
        addAttribute(msg_setip, IFA_BROADCAST, sizeof(bcast_addr), &bcast_addr);

        // No matter what happens, we return since we found the link we've been looking for.
        if (!sendMessage(msg_setip)) {
            // TODO: pton to print ip number also.
            fprintf(stderr, "Failed to set ip on link %i\n", ifinfo.ifi_index);
            return false;
        } else {
            return true;
        }
    }

    // No link found, that's a failure.
    return false;
}

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bool softwarecontainer::Netlink::findLink	(	const char *	ifaceName,
		LinkInfo &	linkInfo
	)

Check that the device given is a network bridge.

Parameters

ifaceName	the name of the interface
ifaceIndex	the index of the interface (out parameter)

Returns

true if interface with matching name was found.

false otherwise.

Definition at line 289 of file netlink.cpp.

References checkKernelDump().

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    if (!checkKernelDump()) {
        return false;
    }

    for (LinkInfo link : m_links) {
        AttributeList attributes = link.second;
        for (AttributeInfo attrinfo : attributes) {
            rtattr attr = attrinfo.first;
            void *data = attrinfo.second;

            if (attr.rta_type == IFLA_IFNAME) {
                char *ifname = (char *) data;
                if (strcmp(ifname, ifaceName) == 0) {
                    linkInfo = link;
                    return true;
                }
            }
        }
    }

    return false;
}

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bool softwarecontainer::Netlink::findAddresses	(	const unsigned int	interfaceIndex,
		std::vector< AddressInfo > &	result
	)

Get all addresses associated with the given interface index.

Parameters

interfaceIndex	the interface address to get addresses for
result	the vector to place all addresses in (out parameter)

Returns

true on success

false otherwise

Definition at line 314 of file netlink.cpp.

References checkKernelDump().

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    if (!checkKernelDump()) {
        return false;
    }

    for (AddressInfo addressInfo : m_addresses) {
        ifaddrmsg addrmsg = addressInfo.first;
        if (addrmsg.ifa_index == interfaceIndex) {
            result.push_back(addressInfo);
        }
    }

    return true;

}

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bool softwarecontainer::Netlink::hasAddress	(	const std::vector< AddressInfo > &	haystack,
		const int	addressFamily,
		const char *	needle
	)

checks if an address is present in the given list

Parameters

haystack	the list to search in
addressFamily	the address family, AF_INET or AF_INET6
needle	the ip address to search for, in dotted notation

Returns

true if the address is in the haystack

false otherwise

Definition at line 331 of file netlink.cpp.

Referenced by softwarecontainer::NetworkGateway::teardownGateway().

{
    for (AddressInfo addressInfo : haystack) {
        AttributeList attributes = addressInfo.second;
        for (AttributeInfo attrPair : attributes) {

            // Skip if this attribute is not an address attribute
            rtattr attr = attrPair.first;
            if (attr.rta_type != IFA_ADDRESS && attr.rta_type != IFA_LOCAL) {
                continue;
            }

            void *data = attrPair.second;
            char out[INET6_ADDRSTRLEN];

            // It is ok here for inet_ntop to fail (data could be bad)
            if (inet_ntop(addressFamily, data, out, sizeof(out)) && strcmp(out, needle) == 0) {
                return true;
            }
        }
    }

    std::cout << "Netlink does not have address" << std::endl;
    return false;
}

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---

The documentation for this class was generated from the following files:

• libsoftwarecontainer/src/gateway/network/netlink.h
• libsoftwarecontainer/src/gateway/network/netlink.cpp