how much bandwidth change does this give? is teh timestamp really a big load? fo a 4% increase I wouldn't bother. for a 50% increase I would..
Bruce M Simpson wrote:
Here's a patch against 5.3 to add a per-instance switch which allows the user to specify if captured packets should be timestamped (and, if so, whether microtime() or the faster but less accurate getmicrotime() call should be used).
Comments/flames/etc to the usual...
BMS
------------------------------------------------------------------------
Index: bpf.c =================================================================== RCS file: /home/ncvs/src/sys/net/bpf.c,v retrieving revision 1.130 diff -u -p -r1.130 bpf.c --- bpf.c 5 Jul 2004 16:28:31 -0000 1.130 +++ bpf.c 8 Sep 2004 09:22:09 -0000 @@ -347,6 +347,7 @@ bpfopen(dev, flags, fmt, td) d->bd_bufsize = bpf_bufsize; d->bd_sig = SIGIO; d->bd_seesent = 1; + d->bd_tstamp = BPF_TSTAMP_MICROTIME; #ifdef MAC mac_init_bpfdesc(d); mac_create_bpfdesc(td->td_ucred, d); @@ -629,6 +630,7 @@ reset_d(d) * BIOCSHDRCMPLT Set "header already complete" flag * BIOCGSEESENT Get "see packets sent" flag * BIOCSSEESENT Set "see packets sent" flag + * BIOCSTSTAMP Set "timestamp preference" flag */ /* ARGSUSED */ static int @@ -880,6 +882,13 @@ bpfioctl(dev, cmd, addr, flags, td) d->bd_seesent = *(u_int *)addr; break;
+ /* + * Set "timestamp preference" flag + */ + case BIOCSTSTAMP: + d->bd_tstamp = *(u_int *)addr; + break; + case FIONBIO: /* Non-blocking I/O */ break;
@@ -1331,7 +1340,14 @@ catchpacket(d, pkt, pktlen, snaplen, cpf * Append the bpf header. */ hp = (struct bpf_hdr *)(d->bd_sbuf + curlen); - microtime(&hp->bh_tstamp); + /* + * Only prepend a timestamp if instructed to do so. + * getmicrotime() is less accurate but potentially faster. + */ + if (d->bd_tstamp == BPF_TSTAMP_MICROTIME) + microtime(&hp->bh_tstamp); + else if (d->bd_tstamp == BPF_TSTAMP_GETMICROTIME) + getmicrotime(&hp->bh_tstamp); hp->bh_datalen = pktlen; hp->bh_hdrlen = hdrlen; /* Index: bpf.h =================================================================== RCS file: /home/ncvs/src/sys/net/bpf.h,v retrieving revision 1.36 diff -u -p -r1.36 bpf.h --- bpf.h 30 May 2004 17:03:48 -0000 1.36 +++ bpf.h 8 Sep 2004 09:15:35 -0000 @@ -113,6 +113,7 @@ struct bpf_version { #define BIOCSSEESENT _IOW('B',119, u_int) #define BIOCSDLT _IOW('B',120, u_int) #define BIOCGDLTLIST _IOWR('B',121, struct bpf_dltlist) +#define BIOCSTSTAMP _IOW('B',122, u_int)
/*
* Structure prepended to each packet.
@@ -491,4 +492,13 @@ u_int bpf_filter(const struct bpf_insn */
#define BPF_MEMWORDS 16
+/*
+ * Defines to specify timestamping preference for a BPF instance.
+ * BPF_TSTAMP_MICROTIME is the default when none is specified.
+ * Other settings may increase BPF capture performance under load.
+ */
+#define BPF_TSTAMP_NONE 0x00 /* Don't timestamp packets */
+#define BPF_TSTAMP_MICROTIME 0x01 /* Use microtime() (slower) */
+#define BPF_TSTAMP_GETMICROTIME 0x02 /* Use getmicrotime() */
+
#endif /* _NET_BPF_H_ */
Index: bpfdesc.h
===================================================================
RCS file: /home/ncvs/src/sys/net/bpfdesc.h,v
retrieving revision 1.27
diff -u -p -r1.27 bpfdesc.h
--- bpfdesc.h 7 Apr 2004 20:46:11 -0000 1.27
+++ bpfdesc.h 8 Sep 2004 09:17:16 -0000
@@ -73,6 +73,7 @@ struct bpf_d {
u_char bd_promisc; /* true if listening promiscuously */
u_char bd_state; /* idle, waiting, or timed out */
u_char bd_immediate; /* true to return on packet arrival */
+ u_char bd_tstamp; /* timestamping preferences */
int bd_hdrcmplt; /* false to fill in src lladdr automatically */
int bd_seesent; /* true if bpf should see sent packets */
int bd_async; /* non-zero if packet reception should generate signal */
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