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[ipv4] Extend routing mechanism to handle non-default routes

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Extend the definition of an IPv4 routing table entry to allow for the
expression of non-default gateways for specified off-link subnets, and
of on-link secondary subnets (where we can send directly to the
destination address even though our source address is not within the
subnet).

This more precise definition also allows us to correctly handle
routing in the (uncommon for iPXE) case when multiple network
interfaces are open concurrently and more than one interface has a
default gateway.

The common case of a single IPv4 address/netmask and a default gateway
now results in two routing table entries.  To retain backwards
compatibility with existing documentation (and to avoid on-screen
clutter), the "route" command prints default gateways on the same line
as the locally assigned address.  There is therefore no change in
output from the "route" command unless explicit additional (off-link
or on-link) routes are present.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-06-05 16:49:42 +01:00
parent 96f5864660
commit e648d23fba
4 changed files with 213 additions and 57 deletions
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116
src/net/ipv4.c
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@@ -77,24 +77,32 @@ static struct profiler ipv4_rx_profiler __profiler = { .name = "ipv4.rx" };
*
* @v netdev Network device
* @v address IPv4 address
* @v network Subnet address
* @v netmask Subnet mask
* @v gateway Gateway address (if any)
* @ret rc Return status code
*/
static int add_ipv4_miniroute ( struct net_device *netdev,
struct in_addr address, struct in_addr netmask,
static int ipv4_add_miniroute ( struct net_device *netdev,
struct in_addr address,
struct in_addr network,
struct in_addr netmask,
struct in_addr gateway ) {
struct ipv4_miniroute *miniroute;
struct ipv4_miniroute *before;
struct in_addr hostmask;
struct in_addr broadcast;
/* Calculate host mask */
hostmask.s_addr = ( IN_IS_SMALL ( netmask.s_addr ) ?
INADDR_NONE : ~netmask.s_addr );
broadcast.s_addr = ( address.s_addr | hostmask.s_addr );
if ( gateway.s_addr || IN_IS_SMALL ( netmask.s_addr ) ) {
hostmask.s_addr = INADDR_NONE;
} else {
hostmask.s_addr = ~netmask.s_addr;
}
broadcast.s_addr = ( network.s_addr | hostmask.s_addr );
/* Print debugging information */
DBGC ( netdev, "IPv4 add %s", inet_ntoa ( address ) );
DBGC ( netdev, " for %s", inet_ntoa ( network ) );
DBGC ( netdev, "/%s ", inet_ntoa ( netmask ) );
DBGC ( netdev, "bc %s ", inet_ntoa ( broadcast ) );
if ( gateway.s_addr )
@@ -111,18 +119,49 @@ static int add_ipv4_miniroute ( struct net_device *netdev,
/* Record routing information */
miniroute->netdev = netdev_get ( netdev );
miniroute->address = address;
miniroute->network = network;
miniroute->netmask = netmask;
miniroute->hostmask = hostmask;
miniroute->gateway = gateway;
/* Add to end of list if we have a gateway, otherwise
* to start of list.
*/
if ( gateway.s_addr ) {
list_add_tail ( &miniroute->list, &ipv4_miniroutes );
} else {
list_add ( &miniroute->list, &ipv4_miniroutes );
/* Add to routing table ahead of any less specific routes */
list_for_each_entry ( before, &ipv4_miniroutes, list ) {
if ( netmask.s_addr & ~before->netmask.s_addr )
break;
}
list_add_tail ( &miniroute->list, &before->list );
return 0;
}
/**
* Add IPv4 minirouting table entries
*
* @v netdev Network device
* @v address IPv4 address
* @v netmask Subnet mask
* @v gateway Gateway address (if any)
* @ret rc Return status code
*/
static int ipv4_add_miniroutes ( struct net_device *netdev,
struct in_addr address,
struct in_addr netmask,
struct in_addr gateway ) {
struct in_addr none = { 0 };
struct in_addr network;
int rc;
/* Add local address */
network.s_addr = ( address.s_addr & netmask.s_addr );
if ( ( rc = ipv4_add_miniroute ( netdev, address, network, netmask,
none ) ) != 0 )
return rc;
/* Add default gateway, if applicable */
if ( gateway.s_addr &&
( ( rc = ipv4_add_miniroute ( netdev, address, none, none,
gateway ) ) != 0 ) )
return rc;
return 0;
}
@@ -132,10 +171,11 @@ static int add_ipv4_miniroute ( struct net_device *netdev,
*
* @v miniroute Routing table entry
*/
static void del_ipv4_miniroute ( struct ipv4_miniroute *miniroute ) {
static void ipv4_del_miniroute ( struct ipv4_miniroute *miniroute ) {
struct net_device *netdev = miniroute->netdev;
DBGC ( netdev, "IPv4 del %s", inet_ntoa ( miniroute->address ) );
DBGC ( netdev, " for %s", inet_ntoa ( miniroute->network ) );
DBGC ( netdev, "/%s ", inet_ntoa ( miniroute->netmask ) );
if ( miniroute->gateway.s_addr )
DBGC ( netdev, "gw %s ", inet_ntoa ( miniroute->gateway ) );
@@ -146,6 +186,19 @@ static void del_ipv4_miniroute ( struct ipv4_miniroute *miniroute ) {
free ( miniroute );
}
/**
* Delete IPv4 minirouting table entries
*
*/
static void ipv4_del_miniroutes ( void ) {
struct ipv4_miniroute *miniroute;
struct ipv4_miniroute *tmp;
/* Delete all existing routes */
list_for_each_entry_safe ( miniroute, tmp, &ipv4_miniroutes, list )
ipv4_del_miniroute ( miniroute );
}
/**
* Perform IPv4 routing
*
@@ -170,27 +223,23 @@ struct ipv4_miniroute * ipv4_route ( unsigned int scope_id,
if ( IN_IS_MULTICAST ( dest->s_addr ) ) {
/* If destination is non-global, and the scope ID
* matches this network device, then use this route.
/* If destination is non-global, and the scope
* ID matches this network device, then use
* the first matching route.
*/
if ( miniroute->netdev->scope_id == scope_id )
return miniroute;
} else {
/* If destination is an on-link global
* address, then use this route.
/* If destination is global, then use the
* first matching route (via its gateway if
* specified).
*/
if ( ( ( dest->s_addr ^ miniroute->address.s_addr )
& miniroute->netmask.s_addr ) == 0 )
return miniroute;
/* If destination is an off-link global
* address, and we have a default gateway,
* then use this route.
*/
if ( miniroute->gateway.s_addr ) {
*dest = miniroute->gateway;
if ( ( ( dest->s_addr ^ miniroute->network.s_addr )
& miniroute->netmask.s_addr ) == 0 ) {
if ( miniroute->gateway.s_addr )
*dest = miniroute->gateway;
return miniroute;
}
}
@@ -913,20 +962,17 @@ static int ipv4_settings ( int ( * apply ) ( struct net_device *netdev,
*
* @ret rc Return status code
*/
static int ipv4_create_routes ( void ) {
struct ipv4_miniroute *miniroute;
struct ipv4_miniroute *tmp;
static int ipv4_apply_routes ( void ) {
int rc;
/* Send gratuitous ARPs for any new IPv4 addresses */
ipv4_settings ( ipv4_gratuitous_arp );
/* Delete all existing routes */
list_for_each_entry_safe ( miniroute, tmp, &ipv4_miniroutes, list )
del_ipv4_miniroute ( miniroute );
ipv4_del_miniroutes();
/* Create a route for each configured network device */
if ( ( rc = ipv4_settings ( add_ipv4_miniroute ) ) != 0 )
/* Create routes for each configured network device */
if ( ( rc = ipv4_settings ( ipv4_add_miniroutes ) ) != 0 )
return rc;
return 0;
@@ -934,7 +980,7 @@ static int ipv4_create_routes ( void ) {
/** IPv4 settings applicator */
struct settings_applicator ipv4_settings_applicator __settings_applicator = {
.apply = ipv4_create_routes,
.apply = ipv4_apply_routes,
};
/* Drag in objects via ipv4_protocol */