March 2025 - dev

[PATCH v11 0/4] Reconstruct incoming ICMP headers for failed UDP connect and forward back
by Jon Maloy 13 Oct '25

13 Oct '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. v11: -Eliminated coverity warnings. -Fixed a couple of tab issues (My emacs settings weren't able to handle my combination of whitespace and tab settings correctly.) 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

3 8

[PATCH v2 00/14] Clean up checksum and header generation for inbound packets
by David Gibson 10 Oct '25

10 Oct '25

The main packet "fast paths" for UDP and TCP mostly just forward packets rather than generating them from scratch. However the control paths for ICMP and DHCP sometimes generate packets more or less from scratch. Because these are relatively rare, it's not performance critical. The paths for sending these packets have some duplication of the header generation. There's also some layering violation in tap_ip_send() which both generates IP headers and updates the L4 (UDP or UCMP) checksum. Finally that checksum generation is a little awkward: it temporarily generates the IP pseudo header (or something close enough to serve) in the place of the actual header, generates the checksum, then replaces it with the real IP header. This approach seems to be causing miscompiles with some LTO optimization, because the stores to the pseudo header are being moved or elided across the code calculating the checksum. This series addresses all of these. We consolidate and clarify the packet sending helpers, and use them in some places there was previously duplicated code. In the process we use new checksum generation helpers which take a different approach which should avoid the LTO problems (this aspect I haven't tested yet though). Changes since v1: * Numerous minor style changes * Rename header generation helpers to make their behaviour clearer * Added several missing function doc comments * Corrected some erroneous statements and terms in comments David Gibson (14): Add csum_icmp6() helper for calculating ICMPv6 checksums Add csum_icmp4() helper for calculating ICMP checksums Add csum_udp6() helper for calculating UDP over IPv6 checksums Add csum_udp4() helper for calculating UDP over IPv4 checksums Add csum_ip4_header() helper to calculate IPv4 header checksums Add helpers for normal inbound packet destination addresses Remove support for TCP packets from tap_ip_send() tap: Remove unhelpeful vnet_pre optimization from tap_send() Split tap_ip_send() into IPv4 and IPv6 specific functions tap: Split tap_ip6_send() into UDP and ICMP variants ndp: Remove unneeded eh_source parameter ndp: Use tap_icmp6_send() helper tap: Split tap_ip4_send() into UDP and ICMP variants dhcp: Use tap_udp4_send() helper in dhcp() arp.c | 2 +- checksum.c | 120 ++++++++++++++++----- checksum.h | 15 ++- dhcp.c | 19 +--- dhcpv6.c | 21 +--- icmp.c | 12 +-- ndp.c | 28 +---- ndp.h | 3 +- tap.c | 312 ++++++++++++++++++++++++++++++++++------------------- tap.h | 19 +++- 10 files changed, 345 insertions(+), 206 deletions(-) -- 2.37.3

2 17

[PATCH v3] udp: support traceroute
by Jon Maloy 31 Mar '25

31 Mar '25

Now that ICMP pass-through from socket-to-tap is in place, it is easy to support UDP based traceroute functionality in direction tap-to-socket. We fix that in this commit. Signed-off-by: Jon Maloy <jmaloy(a)redhat.com> --- v2: - Using ancillary data instead of setsockopt to transfer outgoing TTL. - Support IPv6 v3: - Storing ttl per packet instead of per flow. This may not be elegant, but much less intrusive than changing the flow criteria. This eliminates the need for the extra, flow-changing patch we introduced in v2. --- packet.c | 28 +++++++++++++++++----------- packet.h | 30 ++++++++++++++++++++++-------- tap.c | 3 ++- udp.c | 28 ++++++++++++++++++++++++---- udp.h | 3 ++- 5 files changed, 67 insertions(+), 25 deletions(-) diff --git a/packet.c b/packet.c index 72c6158..36a32fe 100644 --- a/packet.c +++ b/packet.c @@ -89,11 +89,12 @@ bool pool_full(const struct pool *p) * @p: Existing pool * @len: Length of new descriptor * @start: Start of data + * @ttl: TTL/hop_limit for this packet * @func: For tracing: name of calling function * @line: For tracing: caller line of function call */ void packet_add_do(struct pool *p, size_t len, const char *start, - const char *func, int line) + const uint8_t ttl, const char *func, int line) { size_t idx = p->count; @@ -106,8 +107,9 @@ void packet_add_do(struct pool *p, size_t len, const char *start, if (packet_check_range(p, start, len, func, line)) return; - p->pkt[idx].iov_base = (void *)start; - p->pkt[idx].iov_len = len; + p->pkt[idx].iov.iov_base = (void *)start; + p->pkt[idx].iov.iov_len = len; + p->pkt[idx].ttl = ttl; p->count++; } @@ -125,7 +127,8 @@ void packet_add_do(struct pool *p, size_t len, const char *start, * Return: pointer to start of data range, NULL on invalid range or descriptor */ void *packet_get_try_do(const struct pool *p, size_t idx, size_t offset, - size_t len, size_t *left, const char *func, int line) + size_t len, size_t *left, uint8_t *ttl, + const char *func, int line) { char *ptr; @@ -139,18 +142,21 @@ void *packet_get_try_do(const struct pool *p, size_t idx, size_t offset, return NULL; } - if (offset > p->pkt[idx].iov_len || - len > (p->pkt[idx].iov_len - offset)) + if (offset > p->pkt[idx].iov.iov_len || + len > (p->pkt[idx].iov.iov_len - offset)) return NULL; - ptr = (char *)p->pkt[idx].iov_base + offset; + ptr = (char *)p->pkt[idx].iov.iov_base + offset; ASSERT_WITH_MSG(!packet_check_range(p, ptr, len, func, line), "Corrupt packet pool, %s:%i", func, line); if (left) - *left = p->pkt[idx].iov_len - offset - len; + *left = p->pkt[idx].iov.iov_len - offset - len; + if (ttl) + *ttl = p->pkt[idx].ttl; +; return ptr; } @@ -168,14 +174,14 @@ void *packet_get_try_do(const struct pool *p, size_t idx, size_t offset, */ void *packet_get_do(const struct pool *p, const size_t idx, size_t offset, size_t len, size_t *left, - const char *func, int line) + uint8_t *ttl, const char *func, int line) { - void *r = packet_get_try_do(p, idx, offset, len, left, func, line); + void *r = packet_get_try_do(p, idx, offset, len, left, ttl, func, line); if (!r) { trace("missing packet data length %zu, offset %zu from " "length %zu, %s:%i", - len, offset, p->pkt[idx].iov_len, func, line); + len, offset, p->pkt[idx].iov.iov_len, func, line); } return r; diff --git a/packet.h b/packet.h index c94780a..1f5142c 100644 --- a/packet.h +++ b/packet.h @@ -11,6 +11,8 @@ /* Maximum size of a single packet stored in pool, including headers */ #define PACKET_MAX_LEN ((size_t)UINT16_MAX) +#define DEFAULT_TTL 64 + /** * struct pool - Generic pool of packets stored in a buffer * @buf: Buffer storing packet descriptors, @@ -26,28 +28,36 @@ struct pool { size_t buf_size; size_t size; size_t count; - struct iovec pkt[]; + struct { + struct iovec iov; + uint8_t ttl; + uint8_t pad[3]; + } pkt[]; }; int vu_packet_check_range(void *buf, const char *ptr, size_t len); void packet_add_do(struct pool *p, size_t len, const char *start, - const char *func, int line); + const uint8_t ttl, const char *func, int line); void *packet_get_try_do(const struct pool *p, const size_t idx, size_t offset, size_t len, size_t *left, - const char *func, int line); + uint8_t *ttl, const char *func, int line); void *packet_get_do(const struct pool *p, const size_t idx, size_t offset, size_t len, size_t *left, - const char *func, int line); + uint8_t *ttl, const char *func, int line); bool pool_full(const struct pool *p); void pool_flush(struct pool *p); #define packet_add(p, len, start) \ - packet_add_do(p, len, start, __func__, __LINE__) + packet_add_do(p, len, start, DEFAULT_TTL, __func__, __LINE__) +#define packet_add_ttl(p, len, start, ttl) \ + packet_add_do(p, len, start, ttl, __func__, __LINE__) #define packet_get_try(p, idx, offset, len, left) \ - packet_get_try_do(p, idx, offset, len, left, __func__, __LINE__) + packet_get_try_do(p, idx, offset, len, left, NULL, __func__, __LINE__) #define packet_get(p, idx, offset, len, left) \ - packet_get_do(p, idx, offset, len, left, __func__, __LINE__) + packet_get_do(p, idx, offset, len, left, NULL, __func__, __LINE__) +#define packet_get_ttl(p, idx, offset, len, left, ttl) \ + packet_get_do(p, idx, offset, len, left, ttl, __func__, __LINE__) #define PACKET_POOL_DECL(_name, _size, _buf) \ struct _name ## _t { \ @@ -55,7 +65,11 @@ struct _name ## _t { \ size_t buf_size; \ size_t size; \ size_t count; \ - struct iovec pkt[_size]; \ + struct { \ + struct iovec iov; \ + uint8_t ttl; \ + uint8_t pad[3]; \ + } pkt[_size]; \ } #define PACKET_POOL_INIT_NOCAST(_size, _buf, _buf_size) \ diff --git a/tap.c b/tap.c index 3a6fcbe..ac9b3df 100644 --- a/tap.c +++ b/tap.c @@ -563,6 +563,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf); * @dest: Destination port * @saddr: Source address * @daddr: Destination address + * @ttl: TTL/hop_limit for packet * @msg: Array of messages that can be handled in a single call */ static struct tap4_l4_t { @@ -821,7 +822,7 @@ resume: #undef L4_SET append: - packet_add((struct pool *)&seq->p, l4len, l4h); + packet_add_ttl((struct pool *)&seq->p, l4len, l4h, iph->ttl); } for (j = 0, seq = tap4_l4; j < seq_count; j++, seq++) { diff --git a/udp.c b/udp.c index 39431d7..5fbba49 100644 --- a/udp.c +++ b/udp.c @@ -859,8 +859,10 @@ fail: */ int udp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, const void *saddr, const void *daddr, - const struct pool *p, int idx, const struct timespec *now) + const struct pool *p, int idx, + const struct timespec *now) { + char ancillary[CMSG_SPACE(sizeof(int))]; const struct flowside *toside; struct mmsghdr mm[UIO_MAXIOV]; union sockaddr_inany to_sa; @@ -885,7 +887,9 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, src = ntohs(uh->source); dst = ntohs(uh->dest); - tosidx = udp_flow_from_tap(c, pif, af, saddr, daddr, src, dst, now); + tosidx = udp_flow_from_tap(c, pif, af, saddr, daddr, + src, dst, now); + if (!(uflow = udp_at_sidx(tosidx))) { char sstr[INET6_ADDRSTRLEN], dstr[INET6_ADDRSTRLEN]; @@ -915,8 +919,9 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, for (i = 0; i < (int)p->count - idx; i++) { struct udphdr *uh_send; size_t len; + uint8_t ttl; - uh_send = packet_get(p, idx + i, 0, sizeof(*uh), &len); + uh_send = packet_get_ttl(p, idx + i, 0, sizeof(*uh), &len, &ttl); if (!uh_send) return p->count - idx; @@ -926,7 +931,6 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, if (len) { m[i].iov_base = (char *)(uh_send + 1); m[i].iov_len = len; - mm[i].msg_hdr.msg_iov = m + i; mm[i].msg_hdr.msg_iovlen = 1; } else { @@ -938,6 +942,22 @@ int udp_tap_handler(const struct ctx *c, uint8_t pif, mm[i].msg_hdr.msg_controllen = 0; mm[i].msg_hdr.msg_flags = 0; + if (ttl != DEFAULT_TTL) { + struct cmsghdr *cmsg = (void *) ancillary; + + if (af == AF_INET) { + cmsg->cmsg_level = IPPROTO_IP; + cmsg->cmsg_type = IP_TTL; + } else { + cmsg->cmsg_level = IPPROTO_IPV6; + cmsg->cmsg_type = IPV6_HOPLIMIT; + } + cmsg->cmsg_len = CMSG_LEN(sizeof(int)); + *((int *) CMSG_DATA(cmsg)) = ttl; + mm[i].msg_hdr.msg_control = ancillary; + mm[i].msg_hdr.msg_controllen = sizeof(ancillary); + } + count++; } diff --git a/udp.h b/udp.h index de2df6d..6adbfcd 100644 --- a/udp.h +++ b/udp.h @@ -15,7 +15,8 @@ void udp_reply_sock_handler(const struct ctx *c, union epoll_ref ref, uint32_t events, const struct timespec *now); int udp_tap_handler(const struct ctx *c, uint8_t pif, sa_family_t af, const void *saddr, const void *daddr, - const struct pool *p, int idx, const struct timespec *now); + const struct pool *p, int idx, + const struct timespec *now); int udp_sock_init(const struct ctx *c, int ns, const union inany_addr *addr, const char *ifname, in_port_t port); int udp_init(struct ctx *c); -- 2.48.1

2 1

[PATCH v2] pasta, passt-repair: Support multiple events per read() in inotify handlers
by David Gibson 30 Mar '25

30 Mar '25

From: Stefano Brivio <sbrivio(a)redhat.com> The current code assumes that we'll get one event per read() on inotify descriptors, but that's not the case, not from documentation, and not from reports. Add loops in the two inotify handlers we have, in pasta-specific code and passt-repair, to go through all the events we receive. Link: https://bugs.passt.top/show_bug.cgi?id=119 Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com> [dwg: Remove unnecessary buffer expansion, use strnlen instead of strlen to make Coverity happier] Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- passt-repair.c | 27 ++++++++++++++++++++------- pasta.c | 20 +++++++++++++------- 2 files changed, 33 insertions(+), 14 deletions(-) diff --git a/passt-repair.c b/passt-repair.c index 120f7aa7..d36c9c94 100644 --- a/passt-repair.c +++ b/passt-repair.c @@ -111,14 +111,14 @@ int main(int argc, char **argv) } if ((sb.st_mode & S_IFMT) == S_IFDIR) { - char buf[sizeof(struct inotify_event) + NAME_MAX + 1]; + char buf[sizeof(struct inotify_event) + NAME_MAX + 1] + __attribute__ ((aligned(__alignof__(struct inotify_event)))); const struct inotify_event *ev; char path[PATH_MAX + 1]; + bool found = false; ssize_t n; int fd; - ev = (struct inotify_event *)buf; - if ((fd = inotify_init1(IN_CLOEXEC)) < 0) { fprintf(stderr, "inotify_init1: %i\n", errno); _exit(1); @@ -130,6 +130,8 @@ int main(int argc, char **argv) } do { + char *p; + n = read(fd, buf, sizeof(buf)); if (n < 0) { fprintf(stderr, "inotify read: %i", errno); @@ -138,11 +140,22 @@ int main(int argc, char **argv) if (n < (ssize_t)sizeof(*ev)) { fprintf(stderr, "Short inotify read: %zi", n); - _exit(1); + continue; + } + + for (p = buf; p < buf + n; p += sizeof(*ev) + ev->len) { + ev = (const struct inotify_event *)p; + + if (ev->len >= REPAIR_EXT_LEN && + !memcmp(ev->name + + strnlen(ev->name, ev->len) - + REPAIR_EXT_LEN, + REPAIR_EXT, REPAIR_EXT_LEN)) { + found = true; + break; + } } - } while (ev->len < REPAIR_EXT_LEN || - memcmp(ev->name + strlen(ev->name) - REPAIR_EXT_LEN, - REPAIR_EXT, REPAIR_EXT_LEN)); + } while (!found); snprintf(path, sizeof(path), "%s/%s", argv[1], ev->name); if ((stat(path, &sb))) { diff --git a/pasta.c b/pasta.c index fa3e7de5..017fa322 100644 --- a/pasta.c +++ b/pasta.c @@ -498,17 +498,23 @@ void pasta_netns_quit_init(const struct ctx *c) */ void pasta_netns_quit_inotify_handler(struct ctx *c, int inotify_fd) { - char buf[sizeof(struct inotify_event) + NAME_MAX + 1]; - const struct inotify_event *in_ev = (struct inotify_event *)buf; + char buf[sizeof(struct inotify_event) + NAME_MAX + 1] + __attribute__ ((aligned(__alignof__(struct inotify_event)))); + const struct inotify_event *ev; + ssize_t n; + char *p; - if (read(inotify_fd, buf, sizeof(buf)) < (ssize_t)sizeof(*in_ev)) + if ((n = read(inotify_fd, buf, sizeof(buf))) < (ssize_t)sizeof(*ev)) return; - if (strncmp(in_ev->name, c->netns_base, sizeof(c->netns_base))) - return; + for (p = buf; p < buf + n; p += sizeof(*ev) + ev->len) { + ev = (const struct inotify_event *)p; - info("Namespace %s is gone, exiting", c->netns_base); - _exit(EXIT_SUCCESS); + if (!strncmp(ev->name, c->netns_base, sizeof(c->netns_base))) { + info("Namespace %s is gone, exiting", c->netns_base); + _exit(EXIT_SUCCESS); + } + } } /** -- 2.49.0

2 2

[PATCH v2 0/2] udp: Fix some minor warts in the ICMP error propagation code
by David Gibson 28 Mar '25

28 Mar '25

While working on using connected sockets for both sides of UDP flows, I spotted a couple of minor problems in the recently added ICMP error propagation code. Here are the fixes. v2: * Rebase and fix conflict with Jon's recent fix in the same code David Gibson (2): udp: Don't attempt to forward ICMP socket errors to other sockets udp: Improve name of UDP related ICMP sending functions udp.c | 40 +++++++++++++++++++++------------------- 1 file changed, 21 insertions(+), 19 deletions(-) -- 2.49.0

2 3

[RFC PATCH] pasta, passt-repair: Support multiple events per read() in inotify handlers
by Stefano Brivio 28 Mar '25

28 Mar '25

The current code assumes that we'll get one event per read() on inotify descriptors, but that's not the case, not from documentation, and not from reports. Add loops in the two inotify handlers we have, in pasta-specific code and passt-repair, to go through all the events we receive. While in pasta the the inotify watch is in an epoll list, and we'll get epoll wakeups as long as there's data to read, in passt-repair that's not the case. So, in pasta we can simply size the buffer for a single event and try to read one, but in passt-repair, we'll need to size the buffer to a safer, reasonable amount of events. Link: https://bugs.passt.top/show_bug.cgi?id=119 Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com> --- I'm posting this as RFC because, while it seems to do the job and I tested all the code paths, Coverity isn't amused by the fact that we assume that inotify 'name' attributes (ev->name) are NULL-terminated. They actually are, but the code is not very robust. Addressing that is kind of trivial but I keep getting it wrong, so I'll start posting this and fix that up later (direct fixes/edits of this patch are also welcome, of course). passt-repair.c | 26 +++++++++++++++++++------- pasta.c | 20 +++++++++++++------- 2 files changed, 32 insertions(+), 14 deletions(-) diff --git a/passt-repair.c b/passt-repair.c index 120f7aa..86581c6 100644 --- a/passt-repair.c +++ b/passt-repair.c @@ -111,14 +111,14 @@ int main(int argc, char **argv) } if ((sb.st_mode & S_IFMT) == S_IFDIR) { - char buf[sizeof(struct inotify_event) + NAME_MAX + 1]; + char buf[(sizeof(struct inotify_event) + NAME_MAX + 1) * 128] + __attribute__ ((aligned(__alignof__(struct inotify_event)))); const struct inotify_event *ev; char path[PATH_MAX + 1]; + bool found = false; ssize_t n; int fd; - ev = (struct inotify_event *)buf; - if ((fd = inotify_init1(IN_CLOEXEC)) < 0) { fprintf(stderr, "inotify_init1: %i\n", errno); _exit(1); @@ -130,6 +130,8 @@ int main(int argc, char **argv) } do { + char *p; + n = read(fd, buf, sizeof(buf)); if (n < 0) { fprintf(stderr, "inotify read: %i", errno); @@ -138,11 +140,21 @@ int main(int argc, char **argv) if (n < (ssize_t)sizeof(*ev)) { fprintf(stderr, "Short inotify read: %zi", n); - _exit(1); + continue; + } + + for (p = buf; p < buf + n; p += sizeof(*ev) + ev->len) { + ev = (const struct inotify_event *)p; + + if (ev->len >= REPAIR_EXT_LEN && + !memcmp(ev->name + strlen(ev->name) - + REPAIR_EXT_LEN, + REPAIR_EXT, REPAIR_EXT_LEN)) { + found = true; + break; + } } - } while (ev->len < REPAIR_EXT_LEN || - memcmp(ev->name + strlen(ev->name) - REPAIR_EXT_LEN, - REPAIR_EXT, REPAIR_EXT_LEN)); + } while (!found); snprintf(path, sizeof(path), "%s/%s", argv[1], ev->name); if ((stat(path, &sb))) { diff --git a/pasta.c b/pasta.c index fa3e7de..017fa32 100644 --- a/pasta.c +++ b/pasta.c @@ -498,17 +498,23 @@ void pasta_netns_quit_init(const struct ctx *c) */ void pasta_netns_quit_inotify_handler(struct ctx *c, int inotify_fd) { - char buf[sizeof(struct inotify_event) + NAME_MAX + 1]; - const struct inotify_event *in_ev = (struct inotify_event *)buf; + char buf[sizeof(struct inotify_event) + NAME_MAX + 1] + __attribute__ ((aligned(__alignof__(struct inotify_event)))); + const struct inotify_event *ev; + ssize_t n; + char *p; - if (read(inotify_fd, buf, sizeof(buf)) < (ssize_t)sizeof(*in_ev)) + if ((n = read(inotify_fd, buf, sizeof(buf))) < (ssize_t)sizeof(*ev)) return; - if (strncmp(in_ev->name, c->netns_base, sizeof(c->netns_base))) - return; + for (p = buf; p < buf + n; p += sizeof(*ev) + ev->len) { + ev = (const struct inotify_event *)p; - info("Namespace %s is gone, exiting", c->netns_base); - _exit(EXIT_SUCCESS); + if (!strncmp(ev->name, c->netns_base, sizeof(c->netns_base))) { + info("Namespace %s is gone, exiting", c->netns_base); + _exit(EXIT_SUCCESS); + } + } } /** -- 2.43.0

2 3

[PATCH v2 0/2] udp: add guest-to-remote traceroute
by Jon Maloy 28 Mar '25

28 Mar '25

We add support for UDP traceroute in the tap-sock direction. More will follow when this one is settled. --- v2: - Added ttl/hop_limit as flow selection criteria - Using ancillary data instead of setsockopt() to pass on ttl/hop_limit. - Added support for IPv6 Jon Maloy (2): Add ttl to outgoing flow structure lookups udp: support traceroute with udp flow.c | 17 ++++++++++++----- flow.h | 8 ++++++-- flow_table.h | 3 ++- icmp.c | 15 ++++++++++----- icmp.h | 2 +- packet.h | 2 ++ tap.c | 25 ++++++++++++++++++------- tcp.c | 6 +++--- udp.c | 31 +++++++++++++++++++++++++++---- udp.h | 3 ++- udp_flow.c | 7 ++++--- udp_flow.h | 2 +- 12 files changed, 88 insertions(+), 33 deletions(-) -- 2.48.1

2 3

[PATCH v2] udp: correct source address for ICMP messages
by Jon Maloy 27 Mar '25

27 Mar '25

While developing traceroute forwarding tap-to-sock we found that struct msghdr.msg_name for the ICMPs in the opposite direction always contains the destination address of the original UDP message, and not, as one might expect, the one of the host which created the error message. Study of the kernel code reveals that this address instead is appended as extra data after the received struct sock_extended_err area. We now change the ICMP receive code accordingly. Fixes: 55431f0077b6 ("udp: create and send ICMPv4 to local peer when applicable") Fixes: 68b04182e07d ("udp: create and send ICMPv6 to local peer when applicable") Signed-off-by: Jon Maloy <jmaloy(a)redhat.com> --- v2: Removed stray comment and unecessary initializations, as per feedback from David Gibson --- udp.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/udp.c b/udp.c index 80520cb..9d16529 100644 --- a/udp.c +++ b/udp.c @@ -510,10 +510,13 @@ static void udp_send_conn_fail_icmp6(const struct ctx *c, */ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref) { - const struct sock_extended_err *ee; + struct errhdr { + struct sock_extended_err ee; + union sockaddr_inany saddr; + }; + const struct errhdr *eh; const struct cmsghdr *hdr; - union sockaddr_inany saddr; - char buf[CMSG_SPACE(sizeof(*ee))]; + char buf[CMSG_SPACE(sizeof(struct errhdr))]; char data[ICMP6_MAX_DLEN]; int s = ref.fd; struct iovec iov = { @@ -521,8 +524,6 @@ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref) .iov_len = sizeof(data) }; struct msghdr mh = { - .msg_name = &saddr, - .msg_namelen = sizeof(saddr), .msg_iov = &iov, .msg_iovlen = 1, .msg_control = buf, @@ -553,7 +554,7 @@ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref) return -1; } - ee = (const struct sock_extended_err *)CMSG_DATA(hdr); + eh = (const struct errhdr *)CMSG_DATA(hdr); if (ref.type == EPOLL_TYPE_UDP_REPLY) { flow_sidx_t sidx = flow_sidx_opposite(ref.flowside); const struct flowside *toside = flowside_at_sidx(sidx); @@ -561,18 +562,19 @@ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref) if (hdr->cmsg_level == IPPROTO_IP) { dlen = MIN(dlen, ICMP4_MAX_DLEN); - udp_send_conn_fail_icmp4(c, ee, toside, saddr.sa4.sin_addr, + udp_send_conn_fail_icmp4(c, &eh->ee, toside, + eh->saddr.sa4.sin_addr, data, dlen); } else if (hdr->cmsg_level == IPPROTO_IPV6) { - udp_send_conn_fail_icmp6(c, ee, toside, - &saddr.sa6.sin6_addr, + udp_send_conn_fail_icmp6(c, &eh->ee, toside, + &eh->saddr.sa6.sin6_addr, data, dlen, sidx.flowi); } } else { trace("Ignoring received IP_RECVERR cmsg on listener socket"); } debug("%s error on UDP socket %i: %s", - str_ee_origin(ee), s, strerror_(ee->ee_errno)); + str_ee_origin(&eh->ee), s, strerror_(eh->ee.ee_errno)); return 1; } -- 2.48.1

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[PATCH v2 0/7] UDP flow socket preliminaries
by David Gibson 27 Mar '25

27 Mar '25

As discussed on our recent call, I'm working towards using connected sockets on both sides of UDP flows. This series makes some preliminary reworks that simplify things and make that easier. v2: * Added patches 5..7, other patches unchanged. David Gibson (7): udp: Common invocation of udp_sock_errs() for vhost-user and "buf" paths udp: Simplify checking of epoll event bits udp_vu: Factor things out of udp_vu_reply_sock_data() loop udp: Share more logic between vu and non-vu reply socket paths udp: Better handling of failure to forward from reply socket udp: Always hash socket facing flowsides udp: Add helper function for creating connected UDP socket udp.c | 121 +++++++++++++++++++++-------------------- udp_flow.c | 143 ++++++++++++++++++++++++++----------------------- udp_internal.h | 2 +- udp_vu.c | 68 +++++++---------------- udp_vu.h | 9 ++-- 5 files changed, 166 insertions(+), 177 deletions(-) -- 2.49.0

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[PATCH 0/2] udp: Fix some minor warts in the ICMP error propagation code
by David Gibson 26 Mar '25

26 Mar '25

While working on using connected sockets for both sides of UDP flows, I spotted a couple of minor problems in the recently added ICMP error propagation code. Here are the fixes. David Gibson (2): udp: Don't attempt to forward ICMP socket errors to other sockets udp: Improve name of UDP related ICMP sending functions udp.c | 38 ++++++++++++++++++++------------------ 1 file changed, 20 insertions(+), 18 deletions(-) -- 2.49.0

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