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Use DSCP for IP QoS traffic classes

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The previous TOS values are deprecated and not used by modern traffic
classifiers. This sets AF21 for "interactive" traffic (with a tty).
Non-tty traffic sets AF11 - that indicates high throughput but is not
lowest priority (which would be CS1 or LE).

This differs from the CS1 used by OpenSSH, it lets interactive git over SSH
have higher priority than background least effort traffic. Dropbear's settings
here should be suitable with the diffservs used by CAKE qdisc.
This commit is contained in:
Matt Johnston 2022-01-25 17:32:20 +08:00
parent 8727f49dec
commit f3a4ea511b
2 changed files with 29 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
channel.h
View File

@ -44,7 +44,7 @@ struct ChanType;
enum dropbear_channel_prio { enum dropbear_channel_prio {
DROPBEAR_CHANNEL_PRIO_INTERACTIVE, /* pty shell, x11 */ DROPBEAR_CHANNEL_PRIO_INTERACTIVE, /* pty shell, x11 */
DROPBEAR_CHANNEL_PRIO_UNKNOWABLE, /* tcp - can't know what's being forwarded */ DROPBEAR_CHANNEL_PRIO_UNKNOWABLE, /* tcp - can't know what's being forwarded */
DROPBEAR_CHANNEL_PRIO_BULK, /* the rest - probably scp or something */ DROPBEAR_CHANNEL_PRIO_BULK, /* the rest - probably scp, rsync, git, or something */
DROPBEAR_CHANNEL_PRIO_EARLY, /* channel is still being set up */ DROPBEAR_CHANNEL_PRIO_EARLY, /* channel is still being set up */
}; };

44
netio.c
View File

@ -363,12 +363,7 @@ void set_listen_fast_open(int sock) {
void set_sock_priority(int sock, enum dropbear_prio prio) { void set_sock_priority(int sock, enum dropbear_prio prio) {
int rc; int rc;
#ifdef IPTOS_LOWDELAY int val;
int iptos_val = 0;
#endif
#ifdef HAVE_LINUX_PKT_SCHED_H
int so_prio_val = 0;
#endif
#if DROPBEAR_FUZZ #if DROPBEAR_FUZZ
if (fuzz.fuzzing) { if (fuzz.fuzzing) {
@ -376,37 +371,54 @@ void set_sock_priority(int sock, enum dropbear_prio prio) {
return; return;
} }
#endif #endif
/* Don't log ENOTSOCK errors so that this can harmlessly be called /* Don't log ENOTSOCK errors so that this can harmlessly be called
* on a client '-J' proxy pipe */ * on a client '-J' proxy pipe */
/* set the TOS bit for either ipv4 or ipv6 */ #ifdef IPTOS_DSCP_AF21
#ifdef IPTOS_LOWDELAY /* Set the DSCP field for outbound IP packet priority.
rfc4594 has some guidance to meanings.
We set AF21 as "Low-Latency" class for interactive (tty session).
Set AF11 "High-Throughput" for bulk data (which includes things
such as git over ssh). We usually want higher priority than
CS1/LE least effort.
OpenSSH at present uses AF21/CS1, rationale
https://cvsweb.openbsd.org/src/usr.bin/ssh/readconf.c#rev1.284
Old Dropbear/OpenSSH and Debian/Ubuntu OpenSSH (at Jan 2022) use
IPTOS_LOWDELAY/IPTOS_THROUGHPUT
*/
if (prio == DROPBEAR_PRIO_LOWDELAY) { if (prio == DROPBEAR_PRIO_LOWDELAY) {
iptos_val = IPTOS_LOWDELAY; val = IPTOS_DSCP_AF21;
} else if (prio == DROPBEAR_PRIO_BULK) { } else if (prio == DROPBEAR_PRIO_BULK) {
iptos_val = IPTOS_THROUGHPUT; val = IPTOS_DSCP_AF11;
} else {
val = 0; /* default */
} }
#if defined(IPPROTO_IPV6) && defined(IPV6_TCLASS) #if defined(IPPROTO_IPV6) && defined(IPV6_TCLASS)
rc = setsockopt(sock, IPPROTO_IPV6, IPV6_TCLASS, (void*)&iptos_val, sizeof(iptos_val)); rc = setsockopt(sock, IPPROTO_IPV6, IPV6_TCLASS, (void*)&val, sizeof(val));
if (rc < 0 && errno != ENOTSOCK) { if (rc < 0 && errno != ENOTSOCK) {
TRACE(("Couldn't set IPV6_TCLASS (%s)", strerror(errno))); TRACE(("Couldn't set IPV6_TCLASS (%s)", strerror(errno)));
} }
#endif #endif
rc = setsockopt(sock, IPPROTO_IP, IP_TOS, (void*)&iptos_val, sizeof(iptos_val)); rc = setsockopt(sock, IPPROTO_IP, IP_TOS, (void*)&val, sizeof(val));
if (rc < 0 && errno != ENOTSOCK) { if (rc < 0 && errno != ENOTSOCK) {
TRACE(("Couldn't set IP_TOS (%s)", strerror(errno))); TRACE(("Couldn't set IP_TOS (%s)", strerror(errno)));
} }
#endif #endif
#ifdef HAVE_LINUX_PKT_SCHED_H #ifdef HAVE_LINUX_PKT_SCHED_H
/* Set scheduling priority within the local Linux network stack */
if (prio == DROPBEAR_PRIO_LOWDELAY) { if (prio == DROPBEAR_PRIO_LOWDELAY) {
so_prio_val = TC_PRIO_INTERACTIVE; val = TC_PRIO_INTERACTIVE;
} else if (prio == DROPBEAR_PRIO_BULK) { } else if (prio == DROPBEAR_PRIO_BULK) {
so_prio_val = TC_PRIO_BULK; val = TC_PRIO_BULK;
} else {
val = 0;
} }
/* linux specific, sets QoS class. see tc-prio(8) */ /* linux specific, sets QoS class. see tc-prio(8) */
rc = setsockopt(sock, SOL_SOCKET, SO_PRIORITY, (void*) &so_prio_val, sizeof(so_prio_val)); rc = setsockopt(sock, SOL_SOCKET, SO_PRIORITY, (void*) &val, sizeof(val));
if (rc < 0 && errno != ENOTSOCK) { if (rc < 0 && errno != ENOTSOCK) {
TRACE(("Couldn't set SO_PRIORITY (%s)", strerror(errno))) TRACE(("Couldn't set SO_PRIORITY (%s)", strerror(errno)))
} }