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([2a01:e0a:e10:ef90:4c84:58cb:a1ef:8b78]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3749efafb30sm1648641f8f.94.2024.08.29.08.08.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Aug 2024 08:08:25 -0700 (PDT) Message-ID: Date: Thu, 29 Aug 2024 17:08:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] fwd, conf: Probe host's ephemeral ports To: David Gibson , passt-dev@passt.top, Stefano Brivio References: <20240829095847.286660-1-david@gibson.dropbear.id.au> <20240829095847.286660-4-david@gibson.dropbear.id.au> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: <20240829095847.286660-4-david@gibson.dropbear.id.au> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: GVLKQVQ6C362UAFKR474LV5ZZOIC3AHE X-Message-ID-Hash: GVLKQVQ6C362UAFKR474LV5ZZOIC3AHE X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 29/08/2024 11:58, David Gibson wrote: > When we forward "all" ports (-t all or -u all), or use an exclude-only > range, we don't actually forward *all* ports - that wouln't leave local > ports to use for outgoing connections. Rather we forward all non-ephemeral > ports - those that won't be used for outgoing connections or datagrams. > > Currently we assume the range of ephemeral ports is that recommended by > RFC 6335, 49152-65535. However, that's not the range used by default on > Linux, 32768-60999 but configurable with the net.ipv4.ip_local_port_range > sysctl. > > We can't really know what range the guest will consider ephemeral, but if > it differs too much from the host it's likely to cause problems we can't > avoid anyway. So, using the host's ephemeral range is a better guess than > using the RFC 6335 range. > > Therefore, add logic to probe the host's ephemeral range, falling back to > the RFC 6335 range if that fails. This has the bonus advantage of > reducing the number of ports bound by -t all -u all on most Linux machines > thereby reducing kernel memory usage. Specifically this reduces kernel > memory usage with -t all -u all from ~380MiB to ~289MiB. > > Signed-off-by: David Gibson > --- > conf.c | 1 + > fwd.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- > fwd.h | 1 + > 3 files changed, 61 insertions(+), 2 deletions(-) > > diff --git a/conf.c b/conf.c > index 3eb117ff..b2758864 100644 > --- a/conf.c > +++ b/conf.c > @@ -1721,6 +1721,7 @@ void conf(struct ctx *c, int argc, char **argv) > /* Inbound port options & DNS can be parsed now (after IPv4/IPv6 > * settings) > */ > + fwd_probe_ephemeral(); > udp_portmap_clear(); > optind = 0; > do { > diff --git a/fwd.c b/fwd.c > index 8fa312a7..a5050980 100644 > --- a/fwd.c > +++ b/fwd.c > @@ -28,8 +28,65 @@ > #include "flow_table.h" > > /* Empheral port range: values from RFC 6335 */ > -static const in_port_t fwd_ephemeral_min = (1 << 15) + (1 << 14); > -static const in_port_t fwd_ephemeral_max = NUM_PORTS - 1; > +static in_port_t fwd_ephemeral_min = (1 << 15) + (1 << 14); > +static in_port_t fwd_ephemeral_max = NUM_PORTS - 1; > + > +#define PORT_RANGE_SYSCTL "/proc/sys/net/ipv4/ip_local_port_range" > + > +/** fwd_probe_ephemeral() - Determine what ports this host considers ephemeral > + * > + * Work out what ports the host thinks are emphemeral and record it for later > + * use by fwd_port_is_ephemeral(). If we're unable to probe, assume the range > + * recommended by RFC 6335. > + */ > +void fwd_probe_ephemeral(void) > +{ > + char *line, *tab, *end; > + struct lineread lr; > + long min, max; > + ssize_t len; > + int fd; > + > + fd = open(PORT_RANGE_SYSCTL, O_RDONLY | O_CLOEXEC); > + if (fd < 0) { > + warn_perror("Unable to open %s", PORT_RANGE_SYSCTL); > + return; > + } > + > + lineread_init(&lr, fd); > + len = lineread_get(&lr, &line); > + close(fd); > + > + if (len < 0) > + goto parse_err; > + > + tab = strchr(line, '\t'); > + if (!tab) > + goto parse_err; > + *tab = '\0'; > + > + errno = 0; > + min = strtol(line, &end, 10); > + if (*end || errno) > + goto parse_err; > + > + errno = 0; > + max = strtol(tab + 1, &end, 10); > + if (*end || errno) > + goto parse_err; > + > + if (min < 0 || min >= NUM_PORTS || > + max < 0 || max >= NUM_PORTS) > + goto parse_err; > + > + fwd_ephemeral_min = min; > + fwd_ephemeral_max = max; > + > + return; > + > +parse_err: > + warn("Unable to parse %s", PORT_RANGE_SYSCTL); > +} > > /** > * fwd_port_is_ephemeral() - Is port number ephemeral? > diff --git a/fwd.h b/fwd.h > index 99dd66cf..3562f3ca 100644 > --- a/fwd.h > +++ b/fwd.h > @@ -12,6 +12,7 @@ struct flowside; > /* Number of ports for both TCP and UDP */ > #define NUM_PORTS (1U << 16) > > +void fwd_probe_ephemeral(void); > bool fwd_port_is_ephemeral(in_port_t port); > > enum fwd_ports_mode { Reviewed-by: Laurent Vivier