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https://github.com/ipxe/ipxe
synced 2026-04-16 03:00:10 +03:00
Verify checksums on the RX datapath.
Simplify checksum generation on the TX datapath.
This commit is contained in:
Michael Brown
+110
-99
@@ -230,44 +230,65 @@ static struct pk_buff * ipv4_reassemble ( struct pk_buff * pkb ) {
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return NULL;
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}
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/**
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* Complete the transport-layer checksum
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* Add IPv4 pseudo-header checksum to existing checksum
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*
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* @v pkb Packet buffer
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* @v tcpip Transport-layer protocol
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*
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* This function calculates the tcpip
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* @v pkb Packet buffer
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* @v csum Existing checksum
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* @ret csum Updated checksum
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*/
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static void ipv4_tx_csum ( struct pk_buff *pkb,
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struct tcpip_protocol *tcpip ) {
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struct iphdr *iphdr = pkb->data;
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static uint16_t ipv4_pshdr_chksum ( struct pk_buff *pkb, uint16_t csum ) {
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struct ipv4_pseudo_header pshdr;
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uint16_t *csum = ( ( ( void * ) iphdr ) + sizeof ( *iphdr )
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+ tcpip->csum_offset );
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struct iphdr *iphdr = pkb->data;
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size_t hdrlen = ( ( iphdr->verhdrlen & IP_MASK_HLEN ) * 4 );
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/* Calculate pseudo header */
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/* Build pseudo-header */
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pshdr.src = iphdr->src;
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pshdr.dest = iphdr->dest;
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pshdr.zero_padding = 0x00;
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pshdr.protocol = iphdr->protocol;
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/* This is only valid when IPv4 does not have options */
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pshdr.len = htons ( pkb_len ( pkb ) - sizeof ( *iphdr ) );
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pshdr.len = htons ( pkb_len ( pkb ) - hdrlen );
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/* Update the checksum value */
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*csum = tcpip_continue_chksum ( *csum, &pshdr, sizeof ( pshdr ) );
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return tcpip_continue_chksum ( csum, &pshdr, sizeof ( pshdr ) );
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}
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/**
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* Calculate the transport-layer checksum while processing packets
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* Determine link-layer address
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*
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* @v dest IPv4 destination address
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* @v src IPv4 source address
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* @v netdev Network device
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* @v ll_dest Link-layer destination address buffer
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* @ret rc Return status code
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*/
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static uint16_t ipv4_rx_csum ( struct pk_buff *pkb __unused,
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uint8_t trans_proto __unused ) {
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/**
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* This function needs to be implemented. Until then, it will return
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* 0xffffffff every time
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*/
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return 0xffff;
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static int ipv4_ll_addr ( struct in_addr dest, struct in_addr src,
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struct net_device *netdev, uint8_t *ll_dest ) {
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struct ll_protocol *ll_protocol = netdev->ll_protocol;
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uint8_t *dest_bytes = ( ( uint8_t * ) &dest );
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if ( dest.s_addr == INADDR_BROADCAST ) {
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/* Broadcast address */
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memcpy ( ll_dest, ll_protocol->ll_broadcast,
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ll_protocol->ll_addr_len );
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return 0;
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} else if ( IN_MULTICAST ( dest.s_addr ) ) {
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/* Special case: IPv4 multicast over Ethernet. This
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* code may need to be generalised once we find out
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* what happens for other link layers.
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*/
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ll_dest[0] = 0x01;
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ll_dest[1] = 0x00;
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ll_dest[2] = 0x5e;
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ll_dest[3] = dest_bytes[1] & 0x7f;
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ll_dest[4] = dest_bytes[2];
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ll_dest[5] = dest_bytes[3];
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return 0;
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} else {
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/* Unicast address: resolve via ARP */
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return arp_resolve ( netdev, &ipv4_protocol, &dest,
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&src, ll_dest );
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}
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}
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/**
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@@ -276,24 +297,23 @@ static uint16_t ipv4_rx_csum ( struct pk_buff *pkb __unused,
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* @v pkb Packet buffer
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* @v tcpip Transport-layer protocol
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* @v st_dest Destination network-layer address
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* @v trans_csum Transport-layer checksum to complete, or NULL
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* @ret rc Status
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*
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* This function expects a transport-layer segment and prepends the IP header
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*/
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static int ipv4_tx ( struct pk_buff *pkb,
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struct tcpip_protocol *tcpip_protocol,
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struct sockaddr_tcpip *st_dest ) {
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struct sockaddr_tcpip *st_dest, uint16_t *trans_csum ) {
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struct iphdr *iphdr = pkb_push ( pkb, sizeof ( *iphdr ) );
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struct sockaddr_in *sin_dest = ( ( struct sockaddr_in * ) st_dest );
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struct ipv4_miniroute *miniroute;
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struct net_device *netdev = NULL;
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struct in_addr next_hop;
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uint8_t ll_dest_buf[MAX_LL_ADDR_LEN];
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const uint8_t *ll_dest = ll_dest_buf;
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uint8_t ll_dest[MAX_LL_ADDR_LEN];
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int rc;
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/* Fill up the IP header, except source address */
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iphdr->verhdrlen = ( ( IP_VER << 4 ) | ( sizeof ( *iphdr ) / 4 ) );
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iphdr->verhdrlen = ( IP_VER | ( sizeof ( *iphdr ) / 4 ) );
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iphdr->service = IP_TOS;
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iphdr->len = htons ( pkb_len ( pkb ) );
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iphdr->ident = htons ( ++next_ident );
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@@ -307,18 +327,23 @@ static int ipv4_tx ( struct pk_buff *pkb,
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next_hop = iphdr->dest;
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miniroute = ipv4_route ( &next_hop );
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if ( ! miniroute ) {
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DBG ( "No route to %s\n", inet_ntoa ( iphdr->dest ) );
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DBG ( "IPv4 has no route to %s\n", inet_ntoa ( iphdr->dest ) );
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rc = -EHOSTUNREACH;
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goto err;
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}
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iphdr->src = miniroute->address;
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netdev = miniroute->netdev;
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/* Calculate the transport layer checksum */
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if ( tcpip_protocol->csum_offset > 0 )
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ipv4_tx_csum ( pkb, tcpip_protocol );
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/* Determine link-layer destination address */
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if ( ( rc = ipv4_ll_addr ( next_hop, iphdr->src, miniroute->netdev,
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ll_dest ) ) != 0 ) {
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DBG ( "IPv4 has no link-layer address for %s\n",
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inet_ntoa ( iphdr->dest ) );
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goto err;
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}
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/* Calculate header checksum, in network byte order */
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/* Fix up checksums */
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if ( trans_csum )
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*trans_csum = ipv4_pshdr_chksum ( pkb, *trans_csum );
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iphdr->chksum = tcpip_chksum ( iphdr, sizeof ( *iphdr ) );
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/* Print IP4 header for debugging */
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@@ -327,34 +352,8 @@ static int ipv4_tx ( struct pk_buff *pkb,
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inet_ntoa ( iphdr->dest ), ntohs ( iphdr->len ), iphdr->protocol,
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ntohs ( iphdr->ident ), ntohs ( iphdr->chksum ) );
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/* Determine link-layer destination address */
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if ( next_hop.s_addr == INADDR_BROADCAST ) {
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/* Broadcast address */
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ll_dest = netdev->ll_protocol->ll_broadcast;
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} else if ( IN_MULTICAST ( next_hop.s_addr ) ) {
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/* Special case: IPv4 multicast over Ethernet. This
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* code may need to be generalised once we find out
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* what happens for other link layers.
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*/
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uint8_t *next_hop_bytes = ( uint8_t * ) &next_hop;
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ll_dest_buf[0] = 0x01;
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ll_dest_buf[0] = 0x00;
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ll_dest_buf[0] = 0x5e;
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ll_dest_buf[3] = next_hop_bytes[1] & 0x7f;
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ll_dest_buf[4] = next_hop_bytes[2];
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ll_dest_buf[5] = next_hop_bytes[3];
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} else {
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/* Unicast address: resolve via ARP */
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if ( ( rc = arp_resolve ( netdev, &ipv4_protocol, &next_hop,
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&iphdr->src, ll_dest_buf ) ) != 0 ) {
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DBG ( "No ARP entry for %s\n",
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inet_ntoa ( iphdr->dest ) );
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goto err;
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}
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}
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/* Hand off to link layer */
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return net_tx ( pkb, netdev, &ipv4_protocol, ll_dest );
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return net_tx ( pkb, miniroute->netdev, &ipv4_protocol, ll_dest );
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err:
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free_pkb ( pkb );
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@@ -374,73 +373,85 @@ static int ipv4_tx ( struct pk_buff *pkb,
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static int ipv4_rx ( struct pk_buff *pkb, struct net_device *netdev __unused,
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const void *ll_source __unused ) {
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struct iphdr *iphdr = pkb->data;
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size_t hdrlen;
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size_t len;
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union {
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struct sockaddr_in sin;
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struct sockaddr_tcpip st;
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} src, dest;
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uint16_t chksum;
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uint16_t csum;
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uint16_t pshdr_csum;
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/* Sanity check */
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/* Sanity check the IPv4 header */
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if ( pkb_len ( pkb ) < sizeof ( *iphdr ) ) {
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DBG ( "IP datagram too short (%d bytes)\n", pkb_len ( pkb ) );
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DBG ( "IPv4 packet too short at %d bytes (min %d bytes)\n",
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pkb_len ( pkb ), sizeof ( *iphdr ) );
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goto err;
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}
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if ( ( iphdr->verhdrlen & IP_MASK_VER ) != IP_VER ) {
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DBG ( "IPv4 version %#02x not supported\n", iphdr->verhdrlen );
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goto err;
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}
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hdrlen = ( ( iphdr->verhdrlen & IP_MASK_HLEN ) * 4 );
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if ( hdrlen < sizeof ( *iphdr ) ) {
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DBG ( "IPv4 header too short at %d bytes (min %d bytes)\n",
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hdrlen, sizeof ( *iphdr ) );
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goto err;
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}
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if ( hdrlen > pkb_len ( pkb ) ) {
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DBG ( "IPv4 header too long at %d bytes "
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"(packet is %d bytes)\n", hdrlen, pkb_len ( pkb ) );
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goto err;
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}
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if ( ( csum = tcpip_chksum ( iphdr, hdrlen ) ) != 0 ) {
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DBG ( "IPv4 checksum incorrect (is %04x including checksum "
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"field, should be 0000)\n", csum );
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goto err;
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}
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len = ntohs ( iphdr->len );
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if ( len < hdrlen ) {
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DBG ( "IPv4 length too short at %d bytes "
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"(header is %d bytes)\n", len, hdrlen );
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goto err;
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}
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if ( len > pkb_len ( pkb ) ) {
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DBG ( "IPv4 length too long at %d bytes "
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"(packet is %d bytes)\n", len, pkb_len ( pkb ) );
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goto err;
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}
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/* Print IP4 header for debugging */
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/* Print IPv4 header for debugging */
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DBG ( "IPv4 RX %s<-", inet_ntoa ( iphdr->dest ) );
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DBG ( "%s len %d proto %d id %04x csum %04x\n",
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inet_ntoa ( iphdr->src ), ntohs ( iphdr->len ), iphdr->protocol,
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ntohs ( iphdr->ident ), ntohs ( iphdr->chksum ) );
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/* Validate version and header length */
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if ( iphdr->verhdrlen != 0x45 ) {
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DBG ( "Bad version and header length %x\n", iphdr->verhdrlen );
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goto err;
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}
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/* Truncate packet to correct length, calculate pseudo-header
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* checksum and then strip off the IPv4 header.
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*/
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pkb_unput ( pkb, ( pkb_len ( pkb ) - len ) );
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pshdr_csum = ipv4_pshdr_chksum ( pkb, TCPIP_EMPTY_CSUM );
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pkb_pull ( pkb, hdrlen );
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/* Validate length of IP packet */
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if ( ntohs ( iphdr->len ) > pkb_len ( pkb ) ) {
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DBG ( "Inconsistent packet length %d\n",
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ntohs ( iphdr->len ) );
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goto err;
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}
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/* Verify the checksum */
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if ( ( chksum = ipv4_rx_csum ( pkb, iphdr->protocol ) ) != 0xffff ) {
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DBG ( "Bad checksum %x\n", chksum );
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}
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/* Fragment reassembly */
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if ( ( iphdr->frags & htons ( IP_MASK_MOREFRAGS ) ) ||
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( ( iphdr->frags & htons ( IP_MASK_OFFSET ) ) != 0 ) ) {
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/* Pass the fragment to the reassembler ipv4_ressable() which
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* either returns a fully reassembled packet buffer or NULL.
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/* Pass the fragment to ipv4_reassemble() which either
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* returns a fully reassembled packet buffer or NULL.
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*/
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pkb = ipv4_reassemble ( pkb );
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if ( !pkb ) {
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if ( ! pkb )
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return 0;
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}
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}
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/* To reduce code size, the following functions are not implemented:
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* 1. Check the destination address
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* 2. Check the TTL field
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* 3. Check the service field
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*/
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/* Construct socket addresses */
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/* Construct socket addresses and hand off to transport layer */
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memset ( &src, 0, sizeof ( src ) );
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src.sin.sin_family = AF_INET;
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src.sin.sin_addr = iphdr->src;
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memset ( &dest, 0, sizeof ( dest ) );
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dest.sin.sin_family = AF_INET;
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dest.sin.sin_addr = iphdr->dest;
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/* Strip header */
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pkb_unput ( pkb, pkb_len ( pkb ) - ntohs ( iphdr->len ) );
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pkb_pull ( pkb, sizeof ( *iphdr ) );
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/* Send it to the transport layer */
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return tcpip_rx ( pkb, iphdr->protocol, &src.st, &dest.st );
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return tcpip_rx ( pkb, iphdr->protocol, &src.st, &dest.st, pshdr_csum);
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err:
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free_pkb ( pkb );
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