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net/tap: add Rx/Tx checksum offload support
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This patch adds basic offloading support, widely expected in a PMD.

Verify IPv4 and UDP/TCP checksums upon packet reception, and set
ol_flags accordingly.

On Tx, set IPv4 and UDP/TCP checksums when required, considering
ol_flags.

Signed-off-by: Pascal Mazon <pascal.mazon@6wind.com>
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Pascal Mazon authored and Ferruh Yigit committed Jun 12, 2017
1 parent f96fe1a commit 8ae3023
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Showing 2 changed files with 131 additions and 0 deletions.
2 changes: 2 additions & 0 deletions doc/guides/nics/features/tap.ini
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@ Promiscuous mode = Y
Allmulticast mode = Y
Basic stats = Y
Flow API = Y
L3 checksum offload = Y
L4 checksum offload = Y
MTU update = Y
Multicast MAC filter = Y
Speed capabilities = Y
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129 changes: 129 additions & 0 deletions drivers/net/tap/rte_eth_tap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@

#include <rte_atomic.h>
#include <rte_branch_prediction.h>
#include <rte_byteorder.h>
#include <rte_common.h>
#include <rte_mbuf.h>
#include <rte_ethdev.h>
Expand All @@ -42,6 +43,7 @@
#include <rte_kvargs.h>
#include <rte_net.h>
#include <rte_debug.h>
#include <rte_ip.h>

#include <sys/types.h>
#include <sys/stat.h>
Expand Down Expand Up @@ -229,6 +231,60 @@ tun_alloc(struct pmd_internals *pmd)
return -1;
}

static void
tap_verify_csum(struct rte_mbuf *mbuf)
{
uint32_t l2 = mbuf->packet_type & RTE_PTYPE_L2_MASK;
uint32_t l3 = mbuf->packet_type & RTE_PTYPE_L3_MASK;
uint32_t l4 = mbuf->packet_type & RTE_PTYPE_L4_MASK;
unsigned int l2_len = sizeof(struct ether_hdr);
unsigned int l3_len;
uint16_t cksum = 0;
void *l3_hdr;
void *l4_hdr;

if (l2 == RTE_PTYPE_L2_ETHER_VLAN)
l2_len += 4;
else if (l2 == RTE_PTYPE_L2_ETHER_QINQ)
l2_len += 8;
/* Don't verify checksum for packets with discontinuous L2 header */
if (unlikely(l2_len + sizeof(struct ipv4_hdr) >
rte_pktmbuf_data_len(mbuf)))
return;
l3_hdr = rte_pktmbuf_mtod_offset(mbuf, void *, l2_len);
if (l3 == RTE_PTYPE_L3_IPV4 || l3 == RTE_PTYPE_L3_IPV4_EXT) {
struct ipv4_hdr *iph = l3_hdr;

/* ihl contains the number of 4-byte words in the header */
l3_len = 4 * (iph->version_ihl & 0xf);
if (unlikely(l2_len + l3_len > rte_pktmbuf_data_len(mbuf)))
return;

cksum = ~rte_raw_cksum(iph, l3_len);
mbuf->ol_flags |= cksum ?
PKT_RX_IP_CKSUM_BAD :
PKT_RX_IP_CKSUM_GOOD;
} else if (l3 == RTE_PTYPE_L3_IPV6) {
l3_len = sizeof(struct ipv6_hdr);
} else {
/* IPv6 extensions are not supported */
return;
}
if (l4 == RTE_PTYPE_L4_UDP || l4 == RTE_PTYPE_L4_TCP) {
l4_hdr = rte_pktmbuf_mtod_offset(mbuf, void *, l2_len + l3_len);
/* Don't verify checksum for multi-segment packets. */
if (mbuf->nb_segs > 1)
return;
if (l3 == RTE_PTYPE_L3_IPV4)
cksum = ~rte_ipv4_udptcp_cksum(l3_hdr, l4_hdr);
else if (l3 == RTE_PTYPE_L3_IPV6)
cksum = ~rte_ipv6_udptcp_cksum(l3_hdr, l4_hdr);
mbuf->ol_flags |= cksum ?
PKT_RX_L4_CKSUM_BAD :
PKT_RX_L4_CKSUM_GOOD;
}
}

/* Callback to handle the rx burst of packets to the correct interface and
* file descriptor(s) in a multi-queue setup.
*/
Expand Down Expand Up @@ -309,6 +365,8 @@ pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
seg->next = NULL;
mbuf->packet_type = rte_net_get_ptype(mbuf, NULL,
RTE_PTYPE_ALL_MASK);
if (rxq->rxmode->hw_ip_checksum)
tap_verify_csum(mbuf);

/* account for the receive frame */
bufs[num_rx++] = mbuf;
Expand All @@ -321,6 +379,56 @@ pmd_rx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
return num_rx;
}

static void
tap_tx_offload(char *packet, uint64_t ol_flags, unsigned int l2_len,
unsigned int l3_len)
{
void *l3_hdr = packet + l2_len;

if (ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_IPV4)) {
struct ipv4_hdr *iph = l3_hdr;
uint16_t cksum;

iph->hdr_checksum = 0;
cksum = rte_raw_cksum(iph, l3_len);
iph->hdr_checksum = (cksum == 0xffff) ? cksum : ~cksum;
}
if (ol_flags & PKT_TX_L4_MASK) {
uint16_t l4_len;
uint32_t cksum;
uint16_t *l4_cksum;
void *l4_hdr;

l4_hdr = packet + l2_len + l3_len;
if ((ol_flags & PKT_TX_L4_MASK) == PKT_TX_UDP_CKSUM)
l4_cksum = &((struct udp_hdr *)l4_hdr)->dgram_cksum;
else if ((ol_flags & PKT_TX_L4_MASK) == PKT_TX_TCP_CKSUM)
l4_cksum = &((struct tcp_hdr *)l4_hdr)->cksum;
else
return;
*l4_cksum = 0;
if (ol_flags & PKT_TX_IPV4) {
struct ipv4_hdr *iph = l3_hdr;

l4_len = rte_be_to_cpu_16(iph->total_length) - l3_len;
cksum = rte_ipv4_phdr_cksum(l3_hdr, 0);
} else {
struct ipv6_hdr *ip6h = l3_hdr;

/* payload_len does not include ext headers */
l4_len = rte_be_to_cpu_16(ip6h->payload_len) -
l3_len + sizeof(struct ipv6_hdr);
cksum = rte_ipv6_phdr_cksum(l3_hdr, 0);
}
cksum += rte_raw_cksum(l4_hdr, l4_len);
cksum = ((cksum & 0xffff0000) >> 16) + (cksum & 0xffff);
cksum = (~cksum) & 0xffff;
if (cksum == 0)
cksum = 0xffff;
*l4_cksum = cksum;
}
}

/* Callback to handle sending packets from the tap interface
*/
static uint16_t
Expand All @@ -341,6 +449,7 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
struct iovec iovecs[mbuf->nb_segs + 1];
struct tun_pi pi = { .flags = 0 };
struct rte_mbuf *seg = mbuf;
char m_copy[mbuf->data_len];
int n;
int j;

Expand All @@ -356,6 +465,19 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
rte_pktmbuf_mtod(seg, void *);
seg = seg->next;
}
if (mbuf->ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_IPV4) ||
(mbuf->ol_flags & PKT_TX_L4_MASK) == PKT_TX_UDP_CKSUM ||
(mbuf->ol_flags & PKT_TX_L4_MASK) == PKT_TX_TCP_CKSUM) {
/* Support only packets with all data in the same seg */
if (mbuf->nb_segs > 1)
break;
/* To change checksums, work on a copy of data. */
rte_memcpy(m_copy, rte_pktmbuf_mtod(mbuf, void *),
rte_pktmbuf_data_len(mbuf));
tap_tx_offload(m_copy, mbuf->ol_flags,
mbuf->l2_len, mbuf->l3_len);
iovecs[1].iov_base = m_copy;
}
/* copy the tx frame data */
n = writev(txq->fd, iovecs, mbuf->nb_segs + 1);
if (n <= 0)
Expand Down Expand Up @@ -533,6 +655,13 @@ tap_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
dev_info->min_rx_bufsize = 0;
dev_info->pci_dev = NULL;
dev_info->speed_capa = tap_dev_speed_capa();
dev_info->rx_offload_capa = (DEV_RX_OFFLOAD_IPV4_CKSUM |
DEV_RX_OFFLOAD_UDP_CKSUM |
DEV_RX_OFFLOAD_TCP_CKSUM);
dev_info->tx_offload_capa =
(DEV_TX_OFFLOAD_IPV4_CKSUM |
DEV_TX_OFFLOAD_UDP_CKSUM |
DEV_TX_OFFLOAD_TCP_CKSUM);
}

static void
Expand Down

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