March 2025 - dev

[PATCH v10 0/4] Reconstruct incoming ICMP headers for failed UDP connect and forward back
by Jon Maloy 05 Mar '25

05 Mar '25

v2: - Added patch breaking out udp header creation from function tap_udp4_send(). - Updated the ICMP creation by using the new function. - Added logics to find correct flow, depending on origin. - All done after feedback from David Gibson. v3: - More changes after feedback from David Gibson. v4: - Even more changes after feedback from D. Gibson v5: - Added corresponding patches for IPv6 v6: - Fixed some small nits after comments from D. Gibson. v7: - Added handling of all rejected ICMP messages - Returning correct user data amount if IPv6 as per RFC 4884. v8: - Added MTU to ICMPv4 ICMP_FRAG_NEEDED messages. - Added ASSERT() validation to message creation functions. v9: - Using real source address of ICMP to complement destination address for originial UDP message when needed. v10: -Fixed wrong l4len value given to tap_push_ip4h() in function udp_send_conn_fail_icmp4(), patch #2. Jon Maloy (4): tap: break out building of udp header from tap_udp4_send function udp: create and send ICMPv4 to local peer when applicable tap: break out building of udp header from tap_udp6_send function udp: create and send ICMPv6 to local peer when applicable tap.c | 86 +++++++++++++++++++++++--------- tap.h | 15 ++++++ udp.c | 132 ++++++++++++++++++++++++++++++++++++++++++++----- udp_internal.h | 2 +- udp_vu.c | 4 +- 5 files changed, 200 insertions(+), 39 deletions(-) -- 2.48.1

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Re: [PATCH v8 2/4] udp: create and send ICMPv4 to local peer when applicable
by 7ppKb5bW 04 Mar '25

04 Mar '25

> +/** > + * udp_send_conn_fail_icmp4() - Construct and send ICMPv4 to local peer > + * @c: Execution context > + * @ee: Extended error descriptor > + * @ref: epoll reference > + * @in: First bytes (max 8) of original UDP message body > + * @dlen: Length of the read part of original UDP message body > + */ > +static void udp_send_conn_fail_icmp4(const struct ctx *c, > + const struct sock_extended_err *ee, > + const struct flowside *toside, > + void *in, size_t dlen) > +{ > + struct in_addr oaddr = toside->oaddr.v4mapped.a4; > + struct in_addr eaddr = toside->eaddr.v4mapped.a4; > + in_port_t eport = toside->eport; > + in_port_t oport = toside->oport; > + struct { > + struct icmphdr icmp4h; > + struct iphdr ip4h; > + struct udphdr uh; > + char data[ICMP4_MAX_DLEN]; > + } __attribute__((packed, aligned(__alignof__(max_align_t)))) msg; > + size_t msglen = sizeof(msg) - sizeof(msg.data) + dlen; > + > + ASSERT(dlen <= ICMP4_MAX_DLEN); > + memset(&msg, 0, sizeof(msg)); > + msg.icmp4h.type = ee->ee_type; > + msg.icmp4h.code = ee->ee_code; > + if (ee->ee_type == ICMP_DEST_UNREACH && ee->ee_code == ICMP_FRAG_NEEDED) > + msg.icmp4h.un.frag.mtu = htons((uint16_t) ee->ee_info); > + > + /* Reconstruct the original headers as returned in the ICMP message */ > + tap_push_ip4h(&msg.ip4h, eaddr, oaddr, dlen, IPPROTO_UDP); > + tap_push_uh4(&msg.uh, eaddr, eport, oaddr, oport, in, dlen); > + memcpy(&msg.data, in, dlen); > + > + tap_icmp4_send(c, oaddr, eaddr, &msg, msglen); > +} The destination IP of the origin packet might not be the source IP of an ICMP error message, if a router sent this ICMP error message. Increase local MTU and try this program: ``` #packet-too-big.py #ip link set eth0 mtu 1520 from socket import * import time IP_RECVERR=0xb IP_MTU_DISCOVER=0xa IP_PMTUDISC_PROBE=0x3 with socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP) as sock: sock.setsockopt(IPPROTO_IP,IP_RECVERR,1) sock.setsockopt(IPPROTO_IP,IP_MTU_DISCOVER,IP_PMTUDISC_PROBE) bigPacket=bytes(1480) sock.sendto(bigPacket,("151.101.1.6",443)) time.sleep(0.1) print(sock.recvmsg(1480,1024,MSG_ERRQUEUE)) ``` > if (ref.type == EPOLL_TYPE_UDP_REPLY) { > flow_sidx_t sidx = flow_sidx_opposite(ref.flowside); > const struct flowside *toside = flowside_at_sidx(sidx); > - > - udp_send_conn_fail_icmp4(c, ee, toside, data, rc); > + size_t dlen = rc; > + > + if (hdr->cmsg_level == IPPROTO_IP) { > + dlen = MIN(dlen, ICMP4_MAX_DLEN); > + udp_send_conn_fail_icmp4(c, ee, toside, data, dlen); > + } else if (hdr->cmsg_level == IPPROTO_IPV6) { > + udp_send_conn_fail_icmp6(c, ee, toside, data, > + dlen, sidx.flowi); > + } > } else { > trace("Ignoring received IP_RECVERR cmsg on listener socket"); > } If the socket is dual-stack, cmsg_level may not match cmsg_data. ``` #dual-stack-test.py from socket import * import time IP_RECVERR=0xb with socket(AF_INET6,SOCK_DGRAM,IPPROTO_UDP) as sock: sock.setsockopt(IPPROTO_IP,IP_RECVERR,1) sock.setsockopt(IPPROTO_IP,IP_TTL,1) packet=bytes(8) sock.sendto(packet,("::ffff:151.101.1.6",443)) time.sleep(0.1) print(sock.recvmsg(1472,1024,MSG_ERRQUEUE)) ```

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[PATCH 0/1] Send RST for guest packets with no flow
by David Gibson 03 Mar '25

03 Mar '25

As we discussed on email, this adds support for sending an RST in response to packets from the guest which don't match an existing flow and are neither SYN (requesting a new connection) nor themselves RST. This is a sligjhtly larger patch than I'd like, but I can't really see a way to simplify it without making fairly extensive reworks to share more code with paths for RST where there is a known connection. That would end up being more churn. David Gibson (1): tcp: Send RST in response to guest packets that match no connection tap.c | 13 +++++------ tap.h | 6 +++++ tcp.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 84 insertions(+), 7 deletions(-) -- 2.48.1

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[PATCH v8 0/4] Reconstruct incoming ICMP headers for failed UDP connect and forward back
by Jon Maloy 03 Mar '25

03 Mar '25

v2: - Added patch breaking out udp header creation from function tap_udp4_send(). - Updated the ICMP creation by using the new function. - Added logics to find correct flow, depending on origin. - All done after feedback from David Gibson. v3: - More changes after feedback from David Gibson. v4: - Even more changes after feedback from D. Gibson v5: - Added corresponding patches for IPv6 v6: - Fixed some small nits after comments from D. Gibson. v7: - Added handling of all rejected ICMP messages - Returning correct user data amount if IPv6 as per RFC 4884. v8: - Added MTU to ICMPv4 ICMP_FRAG_NEEDED messages. - Added ASSERT() validation to message creation functions. Jon Maloy (4): tap: break out building of udp header from tap_udp4_send function udp: create and send ICMPv4 to local peer when applicable tap: break out building of udp header from tap_udp6_send function udp: create and send ICMPv6 to local peer when applicable tap.c | 86 +++++++++++++++++++++++--------- tap.h | 15 ++++++ udp.c | 132 ++++++++++++++++++++++++++++++++++++++++++++----- udp_internal.h | 2 +- udp_vu.c | 4 +- 5 files changed, 200 insertions(+), 39 deletions(-) -- 2.48.1

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[PATCH] pasta.te: fix demo.sh and remove one duplicate rule
by 7ppKb5bW 01 Mar '25

01 Mar '25

On Fedora 41, without "allow pasta_t unconfined_t:dir read" /usr/bin/pasta can't open /proc/[pid]/ns , which is required by pasta_netns_quit_init() . This patch also remove one duplicate rule "allow pasta_t nsfs_t:file read;" , "allow pasta_t nsfs_t:file { open read };" at line 123 is enough. --- contrib/selinux/pasta.te | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/contrib/selinux/pasta.te b/contrib/selinux/pasta.te index 69be081..d0ff0cc 100644 --- a/contrib/selinux/pasta.te +++ b/contrib/selinux/pasta.te @@ -171,7 +171,7 @@ allow pasta_t init_t:lnk_file read; allow pasta_t init_t:unix_stream_socket connectto; allow pasta_t init_t:dbus send_msg; allow pasta_t init_t:system status; -allow pasta_t unconfined_t:dir search; +allow pasta_t unconfined_t:dir { read search }; allow pasta_t unconfined_t:file read; allow pasta_t unconfined_t:lnk_file read; allow pasta_t self:process { setpgid setcap }; @@ -192,8 +192,6 @@ allow pasta_t sysctl_net_t:dir search; allow pasta_t sysctl_net_t:file { open read write }; allow pasta_t kernel_t:system module_request; -allow pasta_t nsfs_t:file read; - allow pasta_t proc_t:dir mounton; allow pasta_t proc_t:filesystem mount; allow pasta_t net_conf_t:lnk_file read; --

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