diff --git a/man/man8/tc-netem.8 b/man/man8/tc-netem.8 index f2cd86b6..8d485b02 100644 --- a/man/man8/tc-netem.8 +++ b/man/man8/tc-netem.8 @@ -8,7 +8,8 @@ NetEm \- Network Emulator .I OPTIONS .IR OPTIONS " := [ " LIMIT " ] [ " DELAY " ] [ " LOSS \ -" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ][ " RATE " ]" +" ] [ " CORRUPT " ] [ " DUPLICATION " ] [ " REORDERING " ] [ " RATE \ +" ] [ " SLOT " ]" .IR LIMIT " := " .B limit @@ -51,6 +52,14 @@ NetEm \- Network Emulator .B rate .IR RATE " [ " PACKETOVERHEAD " [ " CELLSIZE " [ " CELLOVERHEAD " ]]]]" +.IR SLOT " := " +.BR slot +.IR MIN_DELAY " [ " MAX_DELAY " ] [" +.BR packets +.IR PACKETS " ] [ " +.BR bytes +.IR BYTES " ]" + .SH DESCRIPTION NetEm is an enhancement of the Linux traffic control facilities @@ -162,6 +171,27 @@ granularity avoid a perfect shaping at a specific level. This will show up in an artificial packet compression (bursts). Another influence factor are network adapter buffers which can also add artificial delay. +.SS slot +defer delivering accumulated packets to within a slot, with each available slot +configured with a minimum delay to acquire, and an optional maximum delay. Slot +delays can be specified in nanoseconds, microseconds, milliseconds or seconds +(e.g. 800us). Values for the optional parameters +.I BYTES +will limit the number of bytes delivered per slot, and/or +.I PACKETS +will limit the number of packets delivered per slot. + +These slot options can provide a crude approximation of bursty MACs such as +DOCSIS, WiFi, and LTE. + +Note that slotting is limited by several factors: the kernel clock granularity, +as with a rate, and attempts to deliver many packets within a slot will be +smeared by the timer resolution, and by the underlying native bandwidth also. + +It is possible to combine slotting with a rate, in which case complex behaviors +where either the rate, or the slot limits on bytes or packets per slot, govern +the actual delivered rate. + .SH LIMITATIONS The main known limitation of Netem are related to timer granularity, since Linux is not a real-time operating system. diff --git a/tc/q_netem.c b/tc/q_netem.c index 9f9a9b3d..824018b2 100644 --- a/tc/q_netem.c +++ b/tc/q_netem.c @@ -40,7 +40,10 @@ static void explain(void) " [ loss gemodel PERCENT [R [1-H [1-K]]]\n" \ " [ ecn ]\n" \ " [ reorder PRECENT [CORRELATION] [ gap DISTANCE ]]\n" \ -" [ rate RATE [PACKETOVERHEAD] [CELLSIZE] [CELLOVERHEAD]]\n"); +" [ rate RATE [PACKETOVERHEAD] [CELLSIZE] [CELLOVERHEAD]]\n" \ +" [ slot MIN_DELAY [MAX_DELAY] [packets MAX_PACKETS]" \ +" [bytes MAX_BYTES]]\n" \ + ); } static void explain1(const char *arg) @@ -164,6 +167,7 @@ static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv, struct tc_netem_gimodel gimodel; struct tc_netem_gemodel gemodel; struct tc_netem_rate rate = {}; + struct tc_netem_slot slot = {}; __s16 *dist_data = NULL; __u16 loss_type = NETEM_LOSS_UNSPEC; int present[__TCA_NETEM_MAX] = {}; @@ -412,6 +416,45 @@ static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv, return -1; } } + } else if (matches(*argv, "slot") == 0) { + NEXT_ARG(); + present[TCA_NETEM_SLOT] = 1; + if (get_time64(&slot.min_delay, *argv)) { + explain1("slot min_delay"); + return -1; + } + if (NEXT_IS_NUMBER()) { + NEXT_ARG(); + if (get_time64(&slot.max_delay, *argv) || + slot.max_delay < slot.min_delay) { + explain1("slot max_delay"); + return -1; + } + } else { + slot.max_delay = slot.min_delay; + } + if (NEXT_ARG_OK() && + matches(*(argv+1), "packets") == 0) { + NEXT_ARG(); + if (!NEXT_ARG_OK() || + get_s32(&slot.max_packets, *(argv+1), 0)) { + explain1("slot packets"); + return -1; + } + NEXT_ARG(); + } + if (NEXT_ARG_OK() && + matches(*(argv+1), "bytes") == 0) { + unsigned int max_bytes; + NEXT_ARG(); + if (!NEXT_ARG_OK() || + get_size(&max_bytes, *(argv+1))) { + explain1("slot bytes"); + return -1; + } + slot.max_bytes = (int) max_bytes; + NEXT_ARG(); + } } else if (strcmp(*argv, "help") == 0) { explain(); return -1; @@ -472,6 +515,10 @@ static int netem_parse_opt(struct qdisc_util *qu, int argc, char **argv, addattr_l(n, 1024, TCA_NETEM_CORRUPT, &corrupt, sizeof(corrupt)) < 0) return -1; + if (present[TCA_NETEM_SLOT] && + addattr_l(n, 1024, TCA_NETEM_SLOT, &slot, sizeof(slot)) < 0) + return -1; + if (loss_type != NETEM_LOSS_UNSPEC) { struct rtattr *start; @@ -526,6 +573,7 @@ static int netem_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt) int *ecn = NULL; struct tc_netem_qopt qopt; const struct tc_netem_rate *rate = NULL; + const struct tc_netem_slot *slot = NULL; int len; __u64 rate64 = 0; @@ -586,6 +634,11 @@ static int netem_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt) return -1; rate64 = rta_getattr_u64(tb[TCA_NETEM_RATE64]); } + if (tb[TCA_NETEM_SLOT]) { + if (RTA_PAYLOAD(tb[TCA_NETEM_SLOT]) < sizeof(*slot)) + return -1; + slot = RTA_DATA(tb[TCA_NETEM_SLOT]); + } } fprintf(f, "limit %d", qopt.limit); @@ -659,6 +712,15 @@ static int netem_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt) fprintf(f, " celloverhead %d", rate->cell_overhead); } + if (slot) { + fprintf(f, " slot %s", sprint_time64(slot->min_delay, b1)); + fprintf(f, " %s", sprint_time64(slot->max_delay, b1)); + if (slot->max_packets) + fprintf(f, " packets %d", slot->max_packets); + if (slot->max_bytes) + fprintf(f, " bytes %d", slot->max_bytes); + } + if (ecn) fprintf(f, " ecn ");