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worker-vpn: use TCP_INFO on linux to obtain accurate MTU information

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This provides a more accurate value than the one obtained using the
TCP MSS value. The latter is affected by many factors (such as tcp
options), to provide a reliable value.

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>
This commit is contained in:
Nikos Mavrogiannopoulos
2017-02-23 09:54:05 +01:00
parent fdfad2fa7e
commit 4d9cdf7610
1 changed files with 48 additions and 32 deletions
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80
src/worker-vpn.c
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@@ -48,7 +48,7 @@
#include <signal.h>
#include <poll.h>
#if defined(__linux__) &&!defined(IPV6_PATHMTU)
#if defined(__linux__) && !defined(IPV6_PATHMTU)
# define IPV6_PATHMTU 61
#endif
@@ -942,11 +942,45 @@ void mtu_ok(worker_st * ws)
x += r % diff; \
}
int get_pmtu_approx(worker_st *ws)
{
socklen_t sl;
int ret, e;
#if defined(__linux__) && defined(TCP_INFO)
struct tcp_info ti;
sl = sizeof(ti);
ret = getsockopt(ws->conn_fd, IPPROTO_TCP, TCP_INFO, &ti, &sl);
if (ret == -1) {
e = errno;
oclog(ws, LOG_INFO, "error in getting TCP_INFO: %s",
strerror(e));
return -1;
} else {
return ti.tcpi_pmtu;
}
#else
int max = -1;
sl = sizeof(max);
ret = getsockopt(ws->conn_fd, IPPROTO_TCP, TCP_MAXSEG, &max, &sl);
if (ret == -1) {
e = errno;
oclog(ws, LOG_INFO, "error in getting TCP_MAXSEG: %s",
strerror(e));
return -1;
} else {
MSS_ADJUST(max);
return max;
}
#endif
}
static
int periodic_check(worker_st * ws, struct timespec *tnow, unsigned dpd)
{
socklen_t sl;
int max, e, ret;
int max, ret;
time_t now = tnow->tv_sec;
time_t periodic_check_time = PERIODIC_CHECK_TIME;
@@ -1036,20 +1070,11 @@ int periodic_check(worker_st * ws, struct timespec *tnow, unsigned dpd)
}
if (ws->conn_type != SOCK_TYPE_UNIX && ws->udp_state != UP_DISABLED) {
sl = sizeof(max);
ret = getsockopt(ws->conn_fd, IPPROTO_TCP, TCP_MAXSEG, &max, &sl);
if (ret == -1) {
e = errno;
oclog(ws, LOG_INFO, "error in getting TCP_MAXSEG: %s",
strerror(e));
} else {
MSS_ADJUST(max);
/*oclog(ws, LOG_DEBUG, "TCP MSS is %u", max); */
if (max > 0 && max < ws->link_mtu) {
oclog(ws, LOG_DEBUG, "reducing MTU due to TCP MSS to %u",
max);
link_mtu_set(ws, max);
}
max = get_pmtu_approx(ws);
if (max > 0 && max < ws->link_mtu) {
oclog(ws, LOG_DEBUG, "reducing MTU due to TCP/PMTU to %u",
max);
link_mtu_set(ws, max);
}
}
@@ -1571,7 +1596,7 @@ static int connect_handler(worker_st * ws)
struct http_req_st *req = &ws->req;
struct pollfd pfd[4];
unsigned pfd_size;
int e, max, ret, t;
int max, ret, t;
char *p;
unsigned rnd;
#ifdef HAVE_PPOLL
@@ -1580,7 +1605,6 @@ static int connect_handler(worker_st * ws)
unsigned tls_pending, dtls_pending = 0, i;
struct timespec tnow;
unsigned ip6;
socklen_t sl;
sigset_t emptyset, blockset;
sigemptyset(&blockset);
@@ -1693,19 +1717,11 @@ static int connect_handler(worker_st * ws)
/* Attempt to use the TCP connection maximum segment size to set a more
* precise MTU. */
if (ws->conn_type != SOCK_TYPE_UNIX) {
sl = sizeof(max);
ret = getsockopt(ws->conn_fd, IPPROTO_TCP, TCP_MAXSEG, &max, &sl);
if (ret == -1) {
e = errno;
oclog(ws, LOG_INFO, "error in getting TCP_MAXSEG: %s",
strerror(e));
} else {
MSS_ADJUST(max);
if (max > 0 && max < ws->vinfo.mtu) {
oclog(ws, LOG_INFO,
"reducing MTU due to TCP MSS to %u (from %u)", max, ws->vinfo.mtu);
ws->vinfo.mtu = max;
}
max = get_pmtu_approx(ws);
if (max > 0 && max < ws->vinfo.mtu) {
oclog(ws, LOG_DEBUG, "reducing MTU due to TCP/PMTU to %u",
max);
link_mtu_set(ws, max);
}
}