This is a patch for the stack and the em driver to enable TSO
on CURRENT. Previously I had problems getting it to work, but
this is functional.
I should note that CURRENT is being a pain right now, when
I comment out em in the config the kernel panics coming up,
so I had to substitute this code into the tree. Rather bizarre :)
I have this functionality running on a 6.1 based system, and
our test group is already testing against that driver, so far
things are looking good.
I have designed it so the driver can continue to be built
without support. There is also a sysctl in the stack code
so you can set net.inet.tcp.tso_enable on or off and
compare.
I know there may be some refinements to add in, but I
would like to get this into CURRENT as a start.
Comments?
Jack
--- dist/if_em.h Thu Aug 3 12:05:04 2006
+++ if_em.h Fri Sep 1 15:55:30 2006
@@ -36,6 +36,8 @@
#ifndef _EM_H_DEFINED_
#define _EM_H_DEFINED_
+#define TCP_TSO
+
/* Tunables */
/*
@@ -138,6 +140,11 @@
#define EM_CHECKSUM_FEATURES (CSUM_TCP | CSUM_UDP)
/*
+ * Inform the stack about transmit segmentation offload capabilities.
+ */
+#define EM_TCPSEG_FEATURES CSUM_TCPSEG
+
+/*
* This parameter controls the duration of transmit watchdog timer.
*/
#define EM_TX_TIMEOUT 5 /* set to 5 seconds */
@@ -225,6 +232,7 @@
#define EM_RXBUFFER_16384 16384
#define EM_MAX_SCATTER 64
+#define EM_TSO_SIZE 65535
typedef enum _XSUM_CONTEXT_T {
OFFLOAD_NONE,
@@ -307,6 +315,7 @@
uint32_t txd_cmd;
struct em_buffer *tx_buffer_area;
bus_dma_tag_t txtag; /* dma tag for tx */
+ uint32_t tx_tso; /* last tx was tso */
/*
* Receive definitions
--- dist/if_em.c Fri Aug 4 00:56:33 2006
+++ if_em.c Fri Sep 1 15:58:23 2006
@@ -72,6 +72,8 @@
#include <netinet/tcp.h>
#include <netinet/udp.h>
+#include <machine/in_cksum.h>
+
#include <dev/pci/pcivar.h>
#include <dev/pci/pcireg.h>
#include <dev/em/if_em_hw.h>
@@ -229,6 +231,10 @@
struct mbuf *);
static void em_transmit_checksum_setup(struct adapter *, struct mbuf *,
uint32_t *, uint32_t *);
+#ifdef TCP_TSO
+static boolean_t em_tso_setup(struct adapter *, struct mbuf *, u_int32_t *,
+ uint32_t *);
+#endif
static void em_set_promisc(struct adapter *);
static void em_disable_promisc(struct adapter *);
static void em_set_multi(struct adapter *);
@@ -302,6 +308,7 @@
#define E1000_TICKS_TO_USECS(ticks) ((1024 * (ticks) + 500) / 1000)
#define E1000_USECS_TO_TICKS(usecs) ((1000 * (usecs) + 512) / 1024)
+#define M_TSO_LEN 66
static int em_tx_int_delay_dflt = E1000_TICKS_TO_USECS(EM_TIDV);
static int em_rx_int_delay_dflt = E1000_TICKS_TO_USECS(EM_RDTR);
@@ -1061,11 +1068,14 @@
ifp->if_drv_flags |= IFF_DRV_RUNNING;
ifp->if_drv_flags &= ~IFF_DRV_OACTIVE;
+ ifp->if_hwassist = 0;
if (adapter->hw.mac_type >= em_82543) {
if (ifp->if_capenable & IFCAP_TXCSUM)
ifp->if_hwassist = EM_CHECKSUM_FEATURES;
- else
- ifp->if_hwassist = 0;
+#ifdef TCP_TSO
+ if (ifp->if_capenable & IFCAP_TCPSEG)
+ ifp->if_hwassist |= EM_TCPSEG_FEATURES;
+#endif
}
callout_reset(&adapter->timer, hz, em_local_timer, adapter);
@@ -1416,11 +1426,17 @@
struct m_tag *mtag;
uint32_t txd_upper, txd_lower, txd_used, txd_saved;
int nsegs, i, j;
- int error;
+ int error, do_tso, tso_desc = 0;
m_head = *m_headp;
current_tx_desc = NULL;
- txd_used = txd_saved = 0;
+ txd_upper = txd_lower = txd_used = txd_saved = 0;
+
+#ifdef TCP_TSO
+ do_tso = ((m_head->m_pkthdr.csum_flags & CSUM_TCPSEG) != 0);
+#else
+ do_tso = 0;
+#endif
/*
* Force a cleanup if number of TX descriptors
@@ -1473,6 +1489,17 @@
*m_headp = m_head;
}
+ /*
+ * TSO workaround:
+ * If an mbuf is only header we need
+ * to pull 4 bytes of data into it.
+ */
+ if (do_tso && (m_head->m_len <= M_TSO_LEN)) {
+ m_head = m_pullup(m_head, M_TSO_LEN + 4);
+ if (m_head == NULL)
+ return (ENOBUFS);
+ }
+
/*
* Map the packet for DMA.
*/
@@ -1487,23 +1514,43 @@
}
KASSERT(nsegs != 0, ("em_encap: empty packet"));
- if (nsegs > adapter->num_tx_desc_avail) {
+ /*
+ * TSO Hardware workaround, if this packet is not
+ * TSO, and is only a single descriptor long, and
+ * it follows a TSO burst, then we need to add a
+ * sentinel descriptor to prevent premature writeback.
+ */
+ if ((do_tso == 0) && (adapter->tx_tso == TRUE)) {
+ if (nsegs == 1)
+ tso_desc = TRUE;
+ adapter->tx_tso = FALSE;
+ }
+
+ if (nsegs > adapter->num_tx_desc_avail - 2) {
adapter->no_tx_desc_avail2++;
error = ENOBUFS;
goto encap_fail;
}
- if (ifp->if_hwassist > 0)
- em_transmit_checksum_setup(adapter, m_head, &txd_upper, &txd_lower);
- else
- txd_upper = txd_lower = 0;
+ /* Do hardware assists */
+ if ( ifp->if_hwassist > 0) {
+#ifdef TCP_TSO
+ if (em_tso_setup(adapter, m_head, &txd_upper, &txd_lower)) {
+ /* we need to make a final sentinel transmit desc */
+ tso_desc = TRUE;
+ } else
+#endif
+ em_transmit_checksum_setup(adapter, m_head,
+ &txd_upper, &txd_lower);
+ }
i = adapter->next_avail_tx_desc;
- if (adapter->pcix_82544) {
+ if (adapter->pcix_82544)
txd_saved = i;
- txd_used = 0;
- }
+
for (j = 0; j < nsegs; j++) {
+ bus_size_t seg_len;
+ bus_addr_t seg_addr;
/* If adapter is 82544 and on PCIX bus. */
if(adapter->pcix_82544) {
DESC_ARRAY desc_array;
@@ -1537,26 +1584,57 @@
txd_used++;
}
} else {
- tx_buffer = &adapter->tx_buffer_area[i];
- current_tx_desc = &adapter->tx_desc_base[i];
-
- current_tx_desc->buffer_addr = htole64(segs[j].ds_addr);
- current_tx_desc->lower.data = htole32(
- adapter->txd_cmd | txd_lower | segs[j].ds_len);
- current_tx_desc->upper.data = htole32(txd_upper);
-
- if (++i == adapter->num_tx_desc)
- i = 0;
-
- tx_buffer->m_head = NULL;
+ tx_buffer = &adapter->tx_buffer_area[i];
+ current_tx_desc = &adapter->tx_desc_base[i];
+ seg_addr = htole64(segs[j].ds_addr);
+ seg_len = segs[j].ds_len;
+ /*
+ ** TSO Workaround:
+ ** If this is the last descriptor, we want to
+ ** split it so we have a small final sentinel
+ */
+ if (tso_desc && (j == (nsegs -1)) && (seg_len > 8)) {
+ seg_len -= 4;
+ current_tx_desc->buffer_addr = seg_addr;
+ current_tx_desc->lower.data = htole32(
+ adapter->txd_cmd | txd_lower | seg_len);
+ current_tx_desc->upper.data =
+ htole32(txd_upper);
+ if (++i == adapter->num_tx_desc)
+ i = 0;
+ /* Now make the sentinel */
+ ++txd_used; /* using an extra txd */
+ current_tx_desc = &adapter->tx_desc_base[i];
+ tx_buffer = &adapter->tx_buffer_area[i];
+ current_tx_desc->buffer_addr =
+ seg_addr + seg_len;
+ current_tx_desc->lower.data = htole32(
+ adapter->txd_cmd | txd_lower | 4);
+ current_tx_desc->upper.data =
+ htole32(txd_upper);
+ if (++i == adapter->num_tx_desc)
+ i = 0;
+ } else {
+ current_tx_desc->buffer_addr = seg_addr;
+ current_tx_desc->lower.data = htole32(
+ adapter->txd_cmd | txd_lower | seg_len);
+ current_tx_desc->upper.data =
+ htole32(txd_upper);
+ if (++i == adapter->num_tx_desc)
+ i = 0;
+ }
+ tx_buffer->m_head = NULL;
}
}
adapter->next_avail_tx_desc = i;
if (adapter->pcix_82544)
adapter->num_tx_desc_avail -= txd_used;
- else
+ else {
adapter->num_tx_desc_avail -= nsegs;
+ if (tso_desc) /* TSO used an extra for sentinel */
+ adapter->num_tx_desc_avail -= txd_used;
+ }
if (mtag != NULL) {
/* Set the vlan id. */
@@ -2226,6 +2304,15 @@
ifp->if_capenable |= IFCAP_HWCSUM | IFCAP_VLAN_HWCSUM;
}
+#ifdef TCP_TSO
+ /* Enable TSO if available */
+ if ((adapter->hw.mac_type > em_82544) &&
+ (adapter->hw.mac_type != em_82547)) {
+ ifp->if_capabilities |= IFCAP_TCPSEG;
+ ifp->if_capenable |= IFCAP_TCPSEG;
+ }
+#endif
+
/*
* Tell the upper layer(s) we support long frames.
*/
@@ -2436,15 +2523,27 @@
static int
em_setup_transmit_structures(struct adapter *adapter)
{
+#ifdef TCP_TSO
+ struct ifnet *ifp = adapter->ifp;
+#endif
device_t dev = adapter->dev;
struct em_buffer *tx_buffer;
- bus_size_t size;
+ bus_size_t size, segsize;
int error, i;
/*
* Setup DMA descriptor areas.
*/
- size = roundup2(adapter->hw.max_frame_size, MCLBYTES);
+ segsize = size = roundup2(adapter->hw.max_frame_size, MCLBYTES);
+
+#ifdef TCP_TSO
+ /* Overrides for TSO - want large sizes */
+ if (ifp->if_hwassist & EM_TCPSEG_FEATURES) {
+ size = EM_TSO_SIZE;
+ segsize = PAGE_SIZE;
+ }
+#endif
+
if ((error = bus_dma_tag_create(NULL, /* parent */
1, 0, /* alignment, bounds */
BUS_SPACE_MAXADDR, /* lowaddr */
@@ -2452,7 +2551,7 @@
NULL, NULL, /* filter, filterarg */
size, /* maxsize */
EM_MAX_SCATTER, /* nsegments */
- size, /* maxsegsize */
+ segsize, /* maxsegsize */
0, /* flags */
NULL, /* lockfunc */
NULL, /* lockarg */
@@ -2713,6 +2812,87 @@
adapter->next_avail_tx_desc = curr_txd;
}
+#ifdef TCP_TSO
+/**********************************************************************
+ *
+ * Setup work for hardware segmentation offload (TSO)
+ *
+ **********************************************************************/
+static boolean_t
+em_tso_setup(struct adapter *adapter,
+ struct mbuf *mp,
+ u_int32_t *txd_upper,
+ u_int32_t *txd_lower)
+{
+ struct em_context_desc *TXD;
+ struct em_buffer *tx_buffer;
+ struct ip *ip;
+ struct tcphdr *th;
+ int curr_txd, hdr_len, ip_hlen, tcp_hlen;
+
+ if (((mp->m_pkthdr.csum_flags & CSUM_TCPSEG) == 0) ||
+ (mp->m_pkthdr.len <= E1000_TX_BUFFER_SIZE)) {
+ return FALSE;
+ }
+
+ *txd_lower = (E1000_TXD_CMD_DEXT |
+ E1000_TXD_DTYP_D |
+ E1000_TXD_CMD_TSE);
+
+ *txd_upper = (E1000_TXD_POPTS_IXSM |
+ E1000_TXD_POPTS_TXSM) << 8;
+
+ curr_txd = adapter->next_avail_tx_desc;
+ tx_buffer = &adapter->tx_buffer_area[curr_txd];
+ TXD = (struct em_context_desc *) &adapter->tx_desc_base[curr_txd];
+
+ mp->m_data += sizeof(struct ether_header);
+ ip = mtod(mp, struct ip *);
+ ip->ip_len = 0;
+ ip->ip_sum = 0;
+ ip_hlen = ip->ip_hl << 2 ;
+ th = (struct tcphdr *)((caddr_t)ip + ip_hlen);
+ tcp_hlen = th->th_off << 2;
+
+ hdr_len = ETHER_HDR_LEN + ip_hlen + tcp_hlen;
+ th->th_sum = in_pseudo(ip->ip_src.s_addr,
+ ip->ip_dst.s_addr,
+ htons(IPPROTO_TCP));
+
+ mp->m_data -= sizeof(struct ether_header);
+ TXD->lower_setup.ip_fields.ipcss = ETHER_HDR_LEN;
+ TXD->lower_setup.ip_fields.ipcso =
+ ETHER_HDR_LEN + offsetof(struct ip, ip_sum);
+ TXD->lower_setup.ip_fields.ipcse =
+ htole16(ETHER_HDR_LEN + ip_hlen - 1);
+
+ TXD->upper_setup.tcp_fields.tucss =
+ ETHER_HDR_LEN + ip_hlen;
+ TXD->upper_setup.tcp_fields.tucse = 0;
+ TXD->upper_setup.tcp_fields.tucso =
+ ETHER_HDR_LEN + ip_hlen +
+ offsetof(struct tcphdr, th_sum);
+ TXD->tcp_seg_setup.fields.mss = htole16(mp->m_pkthdr.tso_mss);
+ TXD->tcp_seg_setup.fields.hdr_len = hdr_len;
+ TXD->cmd_and_length = htole32(adapter->txd_cmd |
+ E1000_TXD_CMD_DEXT |
+ E1000_TXD_CMD_TSE |
+ E1000_TXD_CMD_IP | E1000_TXD_CMD_TCP |
+ (mp->m_pkthdr.len - (hdr_len)));
+
+ tx_buffer->m_head = NULL;
+
+ if (++curr_txd == adapter->num_tx_desc)
+ curr_txd = 0;
+
+ adapter->num_tx_desc_avail--;
+ adapter->next_avail_tx_desc = curr_txd;
+ adapter->tx_tso = TRUE;
+
+ return TRUE;
+}
+#endif /* TCP_TSO */
+
/**********************************************************************
*
* Examine each tx_buffer in the used queue. If the hardware is done
@@ -3639,6 +3819,12 @@
(long long)adapter->stats.gprc);
device_printf(dev, "Good Packets Xmtd = %lld\n",
(long long)adapter->stats.gptc);
+#ifdef TCP_TSO
+ device_printf(dev, "TSO Contexts Xmtd = %lld\n",
+ (long long)adapter->stats.tsctc);
+ device_printf(dev, "TSO Contexts Failed = %lld\n",
+ (long long)adapter->stats.tsctfc);
+#endif
}
static int
diff -Naur sys.dist/conf/options sys/conf/options
--- sys.dist/conf/options Wed Aug 2 22:19:33 2006
+++ sys/conf/options Thu Aug 31 16:55:23 2006
@@ -386,6 +386,7 @@
SLIP_IFF_OPTS opt_slip.h
TCPDEBUG
TCP_SIGNATURE opt_inet.h
+TCP_TSO opt_global.h
TCP_SACK_DEBUG opt_tcp_sack.h
TCP_DROP_SYNFIN opt_tcp_input.h
DEV_VLAN opt_vlan.h
diff -Naur sys.dist/net/if.h sys/net/if.h
--- sys.dist/net/if.h Mon Jun 19 15:20:44 2006
+++ sys/net/if.h Thu Aug 31 12:33:40 2006
@@ -189,6 +189,7 @@
#define IFCAP_JUMBO_MTU 0x0020 /* 9000 byte MTU supported */
#define IFCAP_POLLING 0x0040 /* driver supports polling */
#define IFCAP_VLAN_HWCSUM 0x0080 /* can do IFCAP_HWCSUM on VLANs */
+#define IFCAP_TCPSEG 0x0100 /* can do TSO */
#define IFCAP_HWCSUM (IFCAP_RXCSUM | IFCAP_TXCSUM)
diff -Naur sys.dist/netinet/ip_output.c sys/netinet/ip_output.c
--- sys.dist/netinet/ip_output.c Thu Jun 29 06:38:36 2006
+++ sys/netinet/ip_output.c Thu Aug 31 15:16:44 2006
@@ -495,9 +495,11 @@
/*
* If small enough for interface, or the interface will take
- * care of the fragmentation for us, can just send directly.
+ * care of the fragmentation for us, or the interface is
+ * doing segmentation, we can just send directly.
*/
- if (ip->ip_len <= ifp->if_mtu || (ifp->if_hwassist & CSUM_FRAGMENT &&
+ if (ip->ip_len <= ifp->if_mtu ||
+ (ifp->if_hwassist & (CSUM_FRAGMENT | CSUM_TCPSEG) &&
((ip->ip_off & IP_DF) == 0))) {
ip->ip_len = htons(ip->ip_len);
ip->ip_off = htons(ip->ip_off);
diff -Naur sys.dist/netinet/tcp_output.c sys/netinet/tcp_output.c
--- sys.dist/netinet/tcp_output.c Thu Feb 23 13:14:34 2006
+++ sys/netinet/tcp_output.c Thu Aug 31 16:50:33 2006
@@ -105,6 +105,12 @@
SYSCTL_INT(_net_inet_tcp, OID_AUTO, newreno, CTLFLAG_RW, &tcp_do_newreno,
0, "Enable NewReno Algorithms");
+#ifdef TCP_TSO
+int tcp_enable_tso = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, tso_enable, CTLFLAG_RW, &tcp_enable_tso,
+ 0, "Enable TCP Segmentation Offload");
+#endif
+
/*
* Tcp output routine: figure out what should be sent and send it.
*/
@@ -130,6 +136,9 @@
#if 0
int maxburst = TCP_MAXBURST;
#endif
+#ifdef TCP_TSO
+ int tso_capable, use_tso;
+#endif
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
int isipv6;
@@ -139,6 +148,10 @@
INP_LOCK_ASSERT(tp->t_inpcb);
+#ifdef TCP_TSO
+ if (tcp_enable_tso)
+ use_tso = tso_capable = tcp_checktso(tp);
+#endif
/*
* Determine length of data that should be transmitted,
* and flags that will be used.
@@ -380,9 +393,22 @@
* no longer contains the last data byte.
*/
if (len > tp->t_maxseg) {
- len = tp->t_maxseg;
+#ifdef TCP_TSO
+ if (use_tso) {
+ /* Even out the transmissions */
+ len = ((ulmin(len, TCP_MAXWIN)/ tp->t_maxseg) *
+ tp->t_maxseg);
+ if (len <= tp->t_maxseg)
+ use_tso = 0;
+ } else
+#endif
+ len = tp->t_maxseg;
sendalot = 1;
}
+#ifdef TCP_TSO
+ else
+ use_tso = 0;
+#endif
if (sack_rxmit) {
if (SEQ_LT(p->rxmit + len, tp->snd_una + so->so_snd.sb_cc))
flags &= ~TH_FIN;
@@ -406,7 +432,7 @@
* - we need to retransmit
*/
if (len) {
- if (len == tp->t_maxseg)
+ if (len >= tp->t_maxseg) /* TSO makes it possible to be greater */
goto send;
/*
* NOTE! on localhost connections an 'ack' from the remote
@@ -703,6 +729,19 @@
* Clear the FIN bit because we cut off the tail of
* the segment.
*/
+#ifdef TCP_TSO
+ if (use_tso) {
+ if (len + optlen + ipoptlen > TCP_MAXWIN) {
+ /*
+ * If there is still more to send,
+ * don't close the connection.
+ */
+ flags &= ~TH_FIN;
+ len = TCP_MAXWIN - optlen - ipoptlen;
+ sendalot = 1;
+ }
+ } else
+#endif
if (len + optlen + ipoptlen > tp->t_maxopd) {
/*
* If there is still more to send, don't close the connection.
@@ -944,6 +983,12 @@
/* IP version must be set here for ipv4/ipv6 checking later */
KASSERT(ip->ip_v == IPVERSION,
("%s: IP version incorrect: %d", __func__, ip->ip_v));
+#ifdef TCP_TSO
+ if (use_tso) { /* Setup for TSO */
+ m->m_pkthdr.tso_mss = tp->t_maxseg;
+ m->m_pkthdr.csum_flags |= CSUM_TCPSEG;
+ }
+#endif
}
/*
@@ -1076,7 +1121,11 @@
* Section 2. However the tcp hostcache migitates the problem
* so it affects only the first tcp connection with a host.
*/
+#ifdef TCP_TSO
+ if (path_mtu_discovery && !use_tso)
+#else
if (path_mtu_discovery)
+#endif
ip->ip_off |= IP_DF;
error = ip_output(m, tp->t_inpcb->inp_options, NULL,
diff -Naur sys.dist/netinet/tcp_subr.c sys/netinet/tcp_subr.c
--- sys.dist/netinet/tcp_subr.c Wed Aug 2 09:18:05 2006
+++ sys/netinet/tcp_subr.c Thu Aug 31 16:54:31 2006
@@ -1643,6 +1643,41 @@
}
#endif /* INET6 */
+#ifdef TCP_TSO
+/*
+ * Find the interface for this tcpcb and determine
+ * if a TSO hardware assist is available.
+ */
+boolean_t
+tcp_checktso(tp)
+ struct tcpcb *tp;
+{
+ struct in_conninfo *inc;
+ struct route sro;
+ struct sockaddr_in *dst;
+ struct ifnet *ifp;
+
+ inc = &tp->t_inpcb->inp_inc;
+ bzero(&sro, sizeof(sro));
+ if (inc->inc_faddr.s_addr != INADDR_ANY) {
+ dst = (struct sockaddr_in *)&sro.ro_dst;
+ dst->sin_family = AF_INET;
+ dst->sin_len = sizeof(*dst);
+ dst->sin_addr = inc->inc_faddr;
+ rtalloc_ign(&sro, RTF_CLONING);
+ }
+ if (sro.ro_rt != NULL) {
+ ifp = sro.ro_rt->rt_ifp;
+ if (ifp->if_hwassist & CSUM_TCPSEG) {
+ RTFREE(sro.ro_rt);
+ return TRUE;
+ }
+ RTFREE(sro.ro_rt);
+ }
+ return FALSE;
+}
+#endif
+
#ifdef IPSEC
/* compute ESP/AH header size for TCP, including outer IP header. */
size_t
diff -Naur sys.dist/netinet/tcp_var.h sys/netinet/tcp_var.h
--- sys.dist/netinet/tcp_var.h Mon Jun 26 08:35:25 2006
+++ sys/netinet/tcp_var.h Thu Aug 31 12:42:25 2006
@@ -510,6 +510,10 @@
u_long tcp_maxmtu6(struct in_conninfo *);
void tcp_mss(struct tcpcb *, int);
int tcp_mssopt(struct in_conninfo *);
+#ifdef TCP_TSO
+boolean_t
+ tcp_checktso(struct tcpcb *);
+#endif
struct inpcb *
tcp_drop_syn_sent(struct inpcb *, int);
struct inpcb *
diff -Naur sys.dist/sys/mbuf.h sys/sys/mbuf.h
--- sys.dist/sys/mbuf.h Sun Jul 23 18:49:57 2006
+++ sys/sys/mbuf.h Thu Aug 31 12:38:04 2006
@@ -110,6 +110,7 @@
/* variables for hardware checksum */
int csum_flags; /* flags regarding checksum */
int csum_data; /* data field used by csum routines */
+ int tso_mss; /* TSO segment size */
SLIST_HEAD(packet_tags, m_tag) tags; /* list of packet tags */
};
@@ -215,6 +216,7 @@
#define CSUM_UDP 0x0004 /* will csum UDP */
#define CSUM_IP_FRAGS 0x0008 /* will csum IP fragments */
#define CSUM_FRAGMENT 0x0010 /* will do IP fragmentation */
+#define CSUM_TCPSEG 0x0020 /* eligible for TCP segmentation */
#define CSUM_IP_CHECKED 0x0100 /* did csum IP */
#define CSUM_IP_VALID 0x0200 /* ... the csum is valid */
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