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tcp, netlink, HAS{BYTES_ACKED,MIN_RTT,GETRANDOM} and NETLINK_GET_STRICT_CHK

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tcpi_bytes_acked and tcpi_min_rtt are only available on recent
kernel versions: provide fall-back paths (incurring some grade of
performance penalty).

Support for getrandom() was introduced in Linux 3.17 and glibc 2.25:
provide an alternate mechanism for that as well, reading from
/dev/random.

Also check if NETLINK_GET_STRICT_CHK is defined before using it:
it's not strictly needed, we'll filter out irrelevant results from
netlink anyway.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2022-01-25 19:55:54 +01:00
parent daf8d057ce
commit 1776de0140
3 changed files with 58 additions and 2 deletions
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15
Makefile
View File

@ -45,6 +45,21 @@ ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
CFLAGS += -DHAS_SND_WND
endif
C := \#include <linux/tcp.h>\nstruct tcp_info x = { .tcpi_bytes_acked = 0 };
ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
CFLAGS += -DHAS_BYTES_ACKED
endif
C := \#include <linux/tcp.h>\nstruct tcp_info x = { .tcpi_min_rtt = 0 };
ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
CFLAGS += -DHAS_MIN_RTT
endif
C := \#include <sys/random.h>\nint main(){int a=getrandom(0, 0, 0);}
ifeq ($(shell printf "$(C)" | $(CC) -S -xc - -o - >/dev/null 2>&1; echo $$?),0)
CFLAGS += -DHAS_GETRANDOM
endif
prefix ?= /usr/local
all: passt pasta passt4netns qrap

9
netlink.c
View File

@ -46,7 +46,10 @@ static int nl_seq;
static int nl_sock_init_do(void *arg)
{
struct sockaddr_nl addr = { .nl_family = AF_NETLINK, };
int *s = &nl_sock, v = 1;
int *s = &nl_sock;
#ifdef NETLINK_GET_STRICT_CHK
int y = 1;
#endif
ns:
if (((*s) = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0 ||
@ -56,7 +59,9 @@ ns:
if (*s == -1 || !arg || s == &nl_sock_ns)
return 0;
setsockopt(*s, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &v, sizeof(v));
#ifdef NETLINK_GET_STRICT_CHK
setsockopt(*s, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &y, sizeof(y));
#endif
ns_enter((struct ctx *)arg);
s = &nl_sock_ns;

36
tcp.c
View File

@ -321,7 +321,9 @@
#include <stddef.h>
#include <string.h>
#include <sys/epoll.h>
#ifdef HAS_GETRANDOM
#include <sys/random.h>
#endif
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/uio.h>
@ -760,6 +762,7 @@ static int tcp_rtt_dst_low(struct tcp_tap_conn *conn)
*/
static void tcp_rtt_dst_check(struct tcp_tap_conn *conn, struct tcp_info *tinfo)
{
#ifdef HAS_MIN_RTT
int i, hole = -1;
if (!tinfo->tcpi_min_rtt ||
@ -777,6 +780,10 @@ static void tcp_rtt_dst_check(struct tcp_tap_conn *conn, struct tcp_info *tinfo)
if (hole == LOW_RTT_TABLE_SIZE)
hole = 0;
memcpy(low_rtt_dst + hole, &in6addr_any, sizeof(conn->a.a6));
#else
(void)conn;
(void)tinfo;
#endif /* HAS_MIN_RTT */
}
/**
@ -1552,6 +1559,13 @@ static int tcp_update_seqack_wnd(struct ctx *c, struct tcp_tap_conn *conn,
struct tcp_info tinfo_new;
int s = conn->sock;
#ifndef HAS_BYTES_ACKED
(void)flags;
conn->seq_ack_to_tap = conn->seq_from_tap;
if (SEQ_LT(conn->seq_ack_to_tap, prev_ack_to_tap))
conn->seq_ack_to_tap = prev_ack_to_tap;
#else
if (conn->state > ESTABLISHED || (flags & (DUP_ACK | FORCE_ACK)) ||
conn->local || tcp_rtt_dst_low(conn) ||
conn->snd_buf < SNDBUF_SMALL) {
@ -1569,6 +1583,7 @@ static int tcp_update_seqack_wnd(struct ctx *c, struct tcp_tap_conn *conn,
if (SEQ_LT(conn->seq_ack_to_tap, prev_ack_to_tap))
conn->seq_ack_to_tap = prev_ack_to_tap;
}
#endif /* !HAS_BYTES_ACKED */
if (!KERNEL_REPORTS_SND_WND(c)) {
tcp_get_sndbuf(conn);
@ -3586,9 +3601,30 @@ int tcp_sock_init(struct ctx *c, struct timespec *now)
{
struct tcp_sock_refill_arg refill_arg = { c, 0 };
int i, port;
#ifndef HAS_GETRANDOM
int dev_random = open("/dev/random", O_RDONLY);
unsigned int random_read = 0;
while (dev_random && random_read < sizeof(c->tcp.hash_secret)) {
int ret = read(dev_random,
(uint8_t *)&c->tcp.hash_secret + random_read,
sizeof(c->tcp.hash_secret) - random_read);
if (ret == -1 && errno == EINTR)
continue;
if (ret <= 0)
break;
random_read += ret;
}
if (dev_random >= 0)
close(dev_random);
if (random_read < sizeof(c->tcp.hash_secret)) {
#else
if (getrandom(&c->tcp.hash_secret, sizeof(c->tcp.hash_secret),
GRND_RANDOM) < 0) {
#endif /* !HAS_GETRANDOM */
perror("TCP initial sequence getrandom");
exit(EXIT_FAILURE);
}