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tcp output MP fixes
Hi,
Next goal is running TCP socket layer with shared netlock. I went
through tcp_output() and looked for MP races. Mostly documentation
and small fixes.
I am not sure about sbchecklowmem(). For MP safety we must serialize
calls to m_pool_used() and protect sblowmem with a mutex. In
practice not much can ever go wrong. I have chosen mtx_enter_try()
to update without spinning and using a possibly obsololete value
in case of lock contention.
ok?
bluhm
Index: kern/uipc_socket2.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/uipc_socket2.c,v
diff -u -p -r1.158 uipc_socket2.c
--- kern/uipc_socket2.c 12 Jul 2024 19:50:35 -0000 1.158
+++ kern/uipc_socket2.c 6 Nov 2024 10:42:27 -0000
@@ -49,6 +49,9 @@
u_long sb_max = SB_MAX; /* patchable */
+struct mutex sblowmem_mtx = MUTEX_INITIALIZER(IPL_SOFTNET);
+int sblowmem;
+
extern struct pool mclpools[];
extern struct pool mbpool;
@@ -683,15 +674,24 @@ sbcheckreserve(u_long cnt, u_long defcnt
int
sbchecklowmem(void)
{
- static int sblowmem;
- unsigned int used = m_pool_used();
+ int lowmem;
+ unsigned int used;
+ if (mtx_enter_try(&sblowmem_mtx) == 0) {
+ /* another thread is updating sblowmem, use old or new value */
+ return (sblowmem);
+ }
+
+ used = m_pool_used();
if (used < 60)
sblowmem = 0;
else if (used > 80)
sblowmem = 1;
+ lowmem = sblowmem;
+
+ mtx_leave(&sblowmem_mtx);
- return (sblowmem);
+ return (lowmem);
}
/*
Index: netinet/in_pcb.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/in_pcb.h,v
diff -u -p -r1.159 in_pcb.h
--- netinet/in_pcb.h 5 Nov 2024 10:49:23 -0000 1.159
+++ netinet/in_pcb.h 5 Nov 2024 23:18:13 -0000
@@ -140,7 +140,7 @@ struct inpcb {
u_int16_t inp_lport; /* [t] local port */
struct socket *inp_socket; /* [I] back pointer to socket */
caddr_t inp_ppcb; /* pointer to per-protocol pcb */
- struct route inp_route; /* cached route */
+ struct route inp_route; /* [s] cached route */
struct refcnt inp_refcnt; /* refcount PCB, delay memory free */
int inp_flags; /* generic IP/datagram flags */
union { /* Header prototype. */
Index: netinet/ip_input.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/ip_input.c,v
diff -u -p -r1.401 ip_input.c
--- netinet/ip_input.c 6 Aug 2024 16:56:09 -0000 1.401
+++ netinet/ip_input.c 5 Nov 2024 23:18:13 -0000
@@ -83,23 +83,16 @@
#include <netinet/ip_carp.h>
#endif
-/*
- * Locks used to protect global variables in this file:
- * I immutable after creation
- * a atomic operations
- * N net lock
- */
-
/* values controllable via sysctl */
-int ip_forwarding = 0; /* [a] */
+int ip_forwarding = 0;
int ipmforwarding = 0;
int ipmultipath = 0;
-int ip_sendredirects = 1; /* [a] */
+int ip_sendredirects = 1;
int ip_dosourceroute = 0;
int ip_defttl = IPDEFTTL;
int ip_mtudisc = 1;
int ip_mtudisc_timeout = IPMTUDISCTIMEOUT;
-int ip_directedbcast = 0; /* [a] */
+int ip_directedbcast = 0;
/* Protects `ipq' and `ip_frags'. */
struct mutex ipq_mutex = MUTEX_INITIALIZER(IPL_SOFTNET);
Index: netinet/ip_var.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/ip_var.h,v
diff -u -p -r1.120 ip_var.h
--- netinet/ip_var.h 12 Jul 2024 19:50:35 -0000 1.120
+++ netinet/ip_var.h 5 Nov 2024 23:18:13 -0000
@@ -36,6 +36,13 @@
#define _NETINET_IP_VAR_H_
/*
+ * Locks used to protect global variables in this file:
+ * I immutable after creation
+ * a atomic operations
+ * N net lock
+ */
+
+/*
* Structure stored in mbuf in inpcb.ip_options
* and passed to ip_output when ip options are in use.
* The actual length of the options (including ipopt_dst)
@@ -216,19 +223,20 @@ extern int ip_defttl; /* default IP tt
#define IPMTUDISCTIMEOUT (10 * 60) /* as per RFC 1191 */
-extern int ip_mtudisc; /* mtu discovery */
+extern int ip_mtudisc; /* [N] mtu discovery */
extern int ip_mtudisc_timeout; /* seconds to timeout mtu discovery */
extern int ipport_firstauto; /* min port for port allocation */
extern int ipport_lastauto; /* max port for port allocation */
extern int ipport_hifirstauto; /* min dynamic/private port number */
extern int ipport_hilastauto; /* max dynamic/private port number */
-extern int ip_forwarding; /* enable IP forwarding */
+extern int ip_forwarding; /* [a] enable IP forwarding */
#ifdef MROUTING
extern int ipmforwarding; /* enable multicast forwarding */
#endif
extern int ipmultipath; /* enable multipath routing */
-extern int ip_directedbcast; /* accept all broadcast packets */
+extern int ip_sendredirects; /* [a] send icmp redirect while forwd */
+extern int ip_directedbcast; /* [a] accept all broadcast packets */
extern unsigned int la_hold_total;
extern const struct pr_usrreqs rip_usrreqs;
Index: netinet/tcp_fsm.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_fsm.h,v
diff -u -p -r1.9 tcp_fsm.h
--- netinet/tcp_fsm.h 5 Feb 2018 14:53:26 -0000 1.9
+++ netinet/tcp_fsm.h 5 Nov 2024 23:18:13 -0000
@@ -68,7 +68,7 @@
* determined by state, with the proviso that TH_FIN is sent only
* if all data queued for output is included in the segment.
*/
-u_char tcp_outflags[TCP_NSTATES] = {
+const u_char tcp_outflags[TCP_NSTATES] = {
TH_RST|TH_ACK, 0, TH_SYN, TH_SYN|TH_ACK,
TH_ACK, TH_ACK,
TH_FIN|TH_ACK, TH_FIN|TH_ACK, TH_FIN|TH_ACK, TH_ACK, TH_ACK,
@@ -76,7 +76,7 @@ u_char tcp_outflags[TCP_NSTATES] = {
#endif /* TCPOUTFLAGS */
#ifdef TCPSTATES
-const char *tcpstates[] = {
+const char *const tcpstates[] = {
"CLOSED", "LISTEN", "SYN_SENT", "SYN_RCVD",
"ESTABLISHED", "CLOSE_WAIT", "FIN_WAIT_1", "CLOSING",
"LAST_ACK", "FIN_WAIT_2", "TIME_WAIT",
Index: netinet/tcp_input.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_input.c,v
diff -u -p -r1.407 tcp_input.c
--- netinet/tcp_input.c 26 Aug 2024 13:55:14 -0000 1.407
+++ netinet/tcp_input.c 5 Nov 2024 23:18:13 -0000
@@ -2788,11 +2788,11 @@ tcp_xmit_timer(struct tcpcb *tp, int32_t
int
tcp_mss(struct tcpcb *tp, int offer)
{
+ struct inpcb *inp;
struct rtentry *rt;
struct ifnet *ifp = NULL;
- int mss, mssopt;
- int iphlen;
- struct inpcb *inp;
+ int mss, mssopt, iphlen, do_rfc3390;
+ u_int rtmtu;
inp = tp->t_inpcb;
@@ -2825,12 +2825,13 @@ tcp_mss(struct tcpcb *tp, int offer)
* if there's an mtu associated with the route and we support
* path MTU discovery for the underlying protocol family, use it.
*/
- if (rt->rt_mtu) {
+ rtmtu = atomic_load_int(&rt->rt_mtu);
+ if (rtmtu) {
/*
* One may wish to lower MSS to take into account options,
* especially security-related options.
*/
- if (tp->pf == AF_INET6 && rt->rt_mtu < IPV6_MMTU) {
+ if (tp->pf == AF_INET6 && rtmtu < IPV6_MMTU) {
/*
* RFC2460 section 5, last paragraph: if path MTU is
* smaller than 1280, use 1280 as packet size and
@@ -2839,8 +2840,7 @@ tcp_mss(struct tcpcb *tp, int offer)
mss = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) -
sizeof(struct tcphdr);
} else {
- mss = rt->rt_mtu - iphlen -
- sizeof(struct tcphdr);
+ mss = rtmtu - iphlen - sizeof(struct tcphdr);
}
} else if (ifp->if_flags & IFF_LOOPBACK) {
mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
@@ -2900,6 +2900,7 @@ tcp_mss(struct tcpcb *tp, int offer)
mss -= TCPOLEN_SIGLEN;
#endif
+ do_rfc3390 = atomic_load_int(&tcp_do_rfc3390);
if (offer == -1) {
/* mss changed due to Path MTU discovery */
tp->t_flags &= ~TF_PMTUD_PEND;
@@ -2914,10 +2915,10 @@ tcp_mss(struct tcpcb *tp, int offer)
tp->snd_cwnd = ulmax((tp->snd_cwnd / tp->t_maxseg) *
mss, mss);
}
- } else if (tcp_do_rfc3390 == 2) {
+ } else if (do_rfc3390 == 2) {
/* increase initial window */
tp->snd_cwnd = ulmin(10 * mss, ulmax(2 * mss, 14600));
- } else if (tcp_do_rfc3390) {
+ } else if (do_rfc3390) {
/* increase initial window */
tp->snd_cwnd = ulmin(4 * mss, ulmax(2 * mss, 4380));
} else
Index: netinet/tcp_output.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_output.c,v
diff -u -p -r1.145 tcp_output.c
--- netinet/tcp_output.c 14 May 2024 09:39:02 -0000 1.145
+++ netinet/tcp_output.c 5 Nov 2024 23:18:13 -0000
@@ -103,8 +103,6 @@
extern struct mbuf *m_copypack();
#endif
-extern int tcprexmtthresh;
-
#ifdef TCP_SACK_DEBUG
void tcp_print_holes(struct tcpcb *tp);
@@ -350,7 +348,7 @@ again:
txmaxseg = ulmin(so->so_snd.sb_hiwat / 2, tp->t_maxseg);
if (len > txmaxseg) {
- if (tcp_do_tso &&
+ if (atomic_load_int(&tcp_do_tso) &&
tp->t_inpcb->inp_options == NULL &&
tp->t_inpcb->inp_outputopts6 == NULL &&
#ifdef TCP_SIGNATURE
Index: netinet/tcp_timer.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_timer.c,v
diff -u -p -r1.76 tcp_timer.c
--- netinet/tcp_timer.c 28 Jan 2024 20:34:25 -0000 1.76
+++ netinet/tcp_timer.c 5 Nov 2024 23:18:13 -0000
@@ -167,10 +167,10 @@ tcp_canceltimers(struct tcpcb *tp)
TCP_TIMER_DISARM(tp, i);
}
-int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
+const int tcp_backoff[TCP_MAXRXTSHIFT + 1] =
{ 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
-int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
+const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */
/*
* TCP timer processing.
Index: netinet/tcp_timer.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_timer.h,v
diff -u -p -r1.21 tcp_timer.h
--- netinet/tcp_timer.h 29 Jan 2024 22:47:13 -0000 1.21
+++ netinet/tcp_timer.h 5 Nov 2024 23:18:13 -0000
@@ -154,13 +154,12 @@ typedef void (*tcp_timer_func_t)(void *)
extern const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS];
extern int tcp_delack_msecs; /* delayed ACK timeout in millisecs */
-extern int tcptv_keep_init;
extern int tcp_always_keepalive; /* assume SO_KEEPALIVE is always set */
extern int tcp_keepidle; /* time before keepalive probes begin */
extern int tcp_keepintvl; /* time between keepalive probes */
extern int tcp_maxidle; /* time to drop after starting probes */
extern int tcp_ttl; /* time to live for TCP segs */
-extern int tcp_backoff[];
+extern const int tcp_backoff[];
void tcp_timer_init(void);
#endif /* _KERNEL */
Index: netinet/tcp_usrreq.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_usrreq.c,v
diff -u -p -r1.231 tcp_usrreq.c
--- netinet/tcp_usrreq.c 12 Apr 2024 16:07:09 -0000 1.231
+++ netinet/tcp_usrreq.c 5 Nov 2024 23:18:13 -0000
@@ -105,12 +105,12 @@
#ifndef TCP_SENDSPACE
#define TCP_SENDSPACE 1024*16
#endif
-u_int tcp_sendspace = TCP_SENDSPACE;
+u_int tcp_sendspace = TCP_SENDSPACE; /* [I] */
#ifndef TCP_RECVSPACE
#define TCP_RECVSPACE 1024*16
#endif
-u_int tcp_recvspace = TCP_RECVSPACE;
-u_int tcp_autorcvbuf_inc = 16 * 1024;
+u_int tcp_recvspace = TCP_RECVSPACE; /* [I] */
+u_int tcp_autorcvbuf_inc = 16 * 1024; /* [I] */
const struct pr_usrreqs tcp_usrreqs = {
.pru_attach = tcp_attach,
@@ -1516,13 +1516,14 @@ tcp_update_sndspace(struct tcpcb *tp)
/* low on memory try to get rid of some */
if (tcp_sendspace < nmax)
nmax = tcp_sendspace;
- } else if (so->so_snd.sb_wat != tcp_sendspace)
+ } else if (so->so_snd.sb_wat != tcp_sendspace) {
/* user requested buffer size, auto-scaling disabled */
nmax = so->so_snd.sb_wat;
- else
+ } else {
/* automatic buffer scaling */
nmax = MIN(sb_max, so->so_snd.sb_wat + tp->snd_max -
tp->snd_una);
+ }
/* a writable socket must be preserved because of poll(2) semantics */
if (sbspace(so, &so->so_snd) >= so->so_snd.sb_lowat) {
@@ -1556,10 +1557,10 @@ tcp_update_rcvspace(struct tcpcb *tp)
/* low on memory try to get rid of some */
if (tcp_recvspace < nmax)
nmax = tcp_recvspace;
- } else if (so->so_rcv.sb_wat != tcp_recvspace)
+ } else if (so->so_rcv.sb_wat != tcp_recvspace) {
/* user requested buffer size, auto-scaling disabled */
nmax = so->so_rcv.sb_wat;
- else {
+ } else {
/* automatic buffer scaling */
if (tp->rfbuf_cnt > so->so_rcv.sb_hiwat / 8 * 7)
nmax = MIN(sb_max, so->so_rcv.sb_hiwat +
Index: netinet/tcp_var.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/netinet/tcp_var.h,v
diff -u -p -r1.178 tcp_var.h
--- netinet/tcp_var.h 13 May 2024 01:15:53 -0000 1.178
+++ netinet/tcp_var.h 5 Nov 2024 23:18:13 -0000
@@ -228,6 +228,7 @@ struct tcp_opt_info {
/*
* Locks used to protect global data and struct members:
* I immutable after creation
+ * a atomic operations
* N net lock
* S syn_cache_mtx tcp syn cache global mutex
*/
@@ -678,16 +679,17 @@ extern const struct pr_usrreqs tcp6_usrr
extern struct pool tcpcb_pool;
extern struct inpcbtable tcbtable, tcb6table; /* queue of active tcpcb's */
extern int tcp_do_rfc1323; /* enabled/disabled? */
+extern int tcprexmtthresh; /* [I] */
extern int tcptv_keep_init; /* [N] time to keep alive initial SYN packet */
-extern int tcp_mssdflt; /* default maximum segment size */
+extern int tcp_mssdflt; /* [N] default maximum segment size */
extern int tcp_rst_ppslim; /* maximum outgoing RST packet per second */
extern int tcp_ack_on_push; /* ACK immediately on PUSH */
extern int tcp_do_sack; /* SACK enabled/disabled */
extern struct pool sackhl_pool;
extern int tcp_sackhole_limit; /* max entries for tcp sack queues */
-extern int tcp_do_ecn; /* RFC3168 ECN enabled/disabled? */
-extern int tcp_do_rfc3390; /* RFC3390 Increasing TCP's Initial Window */
-extern int tcp_do_tso; /* enable TSO for TCP output packets */
+extern int tcp_do_ecn; /* [N] RFC3168 ECN enabled/disabled? */
+extern int tcp_do_rfc3390; /* [a] RFC3390 Increasing TCP Initial Window */
+extern int tcp_do_tso; /* [a] enable TSO for TCP output packets */
extern struct pool tcpqe_pool;
extern int tcp_reass_limit; /* max entries for tcp reass queues */
Index: sys/mbuf.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/sys/mbuf.h,v
diff -u -p -r1.265 mbuf.h
--- sys/mbuf.h 5 Nov 2024 13:15:13 -0000 1.265
+++ sys/mbuf.h 5 Nov 2024 23:18:13 -0000
@@ -411,7 +411,7 @@ struct mbuf_queue {
struct pool;
extern long nmbclust; /* limit on the # of clusters */
-extern int max_linkhdr; /* largest link-level header */
+extern int max_linkhdr; /* [I] largest link-level header */
extern int max_protohdr; /* largest protocol header */
extern int max_hdr; /* largest link+protocol header */
extern struct cpumem *mbstat; /* mbuf statistics counter */
Index: sys/socketvar.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/sys/socketvar.h,v
diff -u -p -r1.134 socketvar.h
--- sys/socketvar.h 9 Sep 2024 07:38:45 -0000 1.134
+++ sys/socketvar.h 5 Nov 2024 23:18:13 -0000
@@ -376,7 +376,7 @@ sbassertlocked(struct sockbuf *sb)
} \
} while (/*CONSTCOND*/0)
-extern u_long sb_max;
+extern u_long sb_max; /* [I] */
extern struct pool socket_pool;
tcp output MP fixes