From 77883fbdd17e836247f746d888dcad3f611a6a59 Mon Sep 17 00:00:00 2001
From: David Gibson <david@gibson.dropbear.id.au>
Date: Wed, 26 Mar 2025 14:44:07 +1100
Subject: [PATCH] udp: Add helper function for creating connected UDP socket
Currently udp_flow_new() open codes creating and connecting a socket to use
for reply messages. We have in mind some more places to use this logic,
plus it just makes for a rather large function. Split this handling out
into a new udp_flow_sock() function.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
---
udp_flow.c | 104 +++++++++++++++++++++++++++++------------------------
1 file changed, 58 insertions(+), 46 deletions(-)
diff --git a/udp_flow.c b/udp_flow.c
index 7e80924..bf4b896 100644
--- a/udp_flow.c
+++ b/udp_flow.c
@@ -61,6 +61,61 @@ void udp_flow_close(const struct ctx *c, struct udp_flow *uflow)
uflow->closed = true;
}
+/**
+ * udp_flow_sock() - Create, bind and connect a flow specific UDP socket
+ * @c: Execution context
+ * @uflow: UDP flow to open socket for
+ * @sidei: Side of @uflow to open socket for
+ *
+ * Return: fd of new socket on success, -ve error code on failure
+ */
+static int udp_flow_sock(const struct ctx *c,
+ const struct udp_flow *uflow, unsigned sidei)
+{
+ const struct flowside *side = &uflow->f.side[sidei];
+ struct mmsghdr discard[UIO_MAXIOV] = { 0 };
+ uint8_t pif = uflow->f.pif[sidei];
+ union {
+ flow_sidx_t sidx;
+ uint32_t data;
+ } fref = { .sidx = FLOW_SIDX(uflow, sidei) };
+ int rc, s;
+
+ s = flowside_sock_l4(c, EPOLL_TYPE_UDP_REPLY, pif, side, fref.data);
+ if (s < 0) {
+ flow_dbg_perror(uflow, "Couldn't open flow specific socket");
+ return s;
+ }
+
+ if (flowside_connect(c, s, pif, side) < 0) {
+ rc = -errno;
+ flow_dbg_perror(uflow, "Couldn't connect flow socket");
+ return rc;
+ }
+
+ /* It's possible, if unlikely, that we could receive some unrelated
+ * packets in between the bind() and connect() of this socket. For now
+ * we just discard these.
+ *
+ * FIXME: Redirect these to an appropriate handler
+ */
+ rc = recvmmsg(s, discard, ARRAY_SIZE(discard), MSG_DONTWAIT, NULL);
+ if (rc >= ARRAY_SIZE(discard)) {
+ flow_dbg(uflow, "Too many (%d) spurious reply datagrams", rc);
+ return -E2BIG;
+ }
+
+ if (rc > 0) {
+ flow_trace(uflow, "Discarded %d spurious reply datagrams", rc);
+ } else if (errno != EAGAIN) {
+ rc = -errno;
+ flow_perror(uflow, "Unexpected error discarding datagrams");
+ return rc;
+ }
+
+ return s;
+}
+
/**
* udp_flow_new() - Common setup for a new UDP flow
* @c: Execution context
@@ -74,13 +129,10 @@ static flow_sidx_t udp_flow_new(const struct ctx *c, union flow *flow,
int s_ini, const struct timespec *now)
{
struct udp_flow *uflow = NULL;
- const struct flowside *tgt;
unsigned sidei;
- uint8_t tgtpif;
- if (!(tgt = flow_target(c, flow, IPPROTO_UDP)))
+ if (!flow_target(c, flow, IPPROTO_UDP))
goto cancel;
- tgtpif = flow->f.pif[TGTSIDE];
uflow = FLOW_SET_TYPE(flow, FLOW_UDP, udp);
uflow->ts = now->tv_sec;
@@ -98,49 +150,9 @@ static flow_sidx_t udp_flow_new(const struct ctx *c, union flow *flow,
}
}
- if (pif_is_socket(tgtpif)) {
- struct mmsghdr discard[UIO_MAXIOV] = { 0 };
- union {
- flow_sidx_t sidx;
- uint32_t data;
- } fref = {
- .sidx = FLOW_SIDX(flow, TGTSIDE),
- };
- int rc;
-
- uflow->s[TGTSIDE] = flowside_sock_l4(c, EPOLL_TYPE_UDP_REPLY,
- tgtpif, tgt, fref.data);
- if (uflow->s[TGTSIDE] < 0) {
- flow_dbg_perror(uflow,
- "Couldn't open socket for spliced flow");
+ if (pif_is_socket(flow->f.pif[TGTSIDE]))
+ if ((uflow->s[TGTSIDE] = udp_flow_sock(c, uflow, TGTSIDE)) < 0)
goto cancel;
- }
-
- if (flowside_connect(c, uflow->s[TGTSIDE], tgtpif, tgt) < 0) {
- flow_dbg_perror(uflow, "Couldn't connect flow socket");
- goto cancel;
- }
-
- /* It's possible, if unlikely, that we could receive some
- * unrelated packets in between the bind() and connect() of this
- * socket. For now we just discard these. We could consider
- * trying to redirect these to an appropriate handler, if we
- * need to.
- */
- rc = recvmmsg(uflow->s[TGTSIDE], discard, ARRAY_SIZE(discard),
- MSG_DONTWAIT, NULL);
- if (rc >= ARRAY_SIZE(discard)) {
- flow_dbg(uflow,
- "Too many (%d) spurious reply datagrams", rc);
- goto cancel;
- } else if (rc > 0) {
- flow_trace(uflow,
- "Discarded %d spurious reply datagrams", rc);
- } else if (errno != EAGAIN) {
- flow_perror(uflow,
- "Unexpected error discarding datagrams");
- }
- }
/* Tap sides always need to be looked up by hash. Socket sides don't
* always, but sometimes do (receiving packets on a socket not specific