From: Jon Maloy <jmaloy@redhat.com>
To: passt-dev@passt.top, sbrivio@redhat.com, lvivier@redhat.com,
dgibson@redhat.com, jmaloy@redhat.com
Subject: [PATCH 2/2] udp: support traceroute for IPv4
Date: Sat, 15 Mar 2025 11:32:45 -0400 [thread overview]
Message-ID: <20250315153245.435293-3-jmaloy@redhat.com> (raw)
In-Reply-To: <20250315153245.435293-1-jmaloy@redhat.com>
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 for IPv4 in this commit.
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
packet.h | 2 ++
tap.c | 8 ++++++--
udp.c | 10 +++++++++-
udp.h | 3 ++-
4 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/packet.h b/packet.h
index d099f02..e406c6d 100644
--- a/packet.h
+++ b/packet.h
@@ -9,6 +9,8 @@
/* Maximum size of a single packet stored in pool, including headers */
#define PACKET_MAX_LEN UINT16_MAX
+#define DEFAULT_TTL 64
+
/**
* struct pool - Generic pool of packets stored in a buffer
* @buf: Buffer storing packet descriptors,
diff --git a/tap.c b/tap.c
index 182a115..7d0970d 100644
--- a/tap.c
+++ b/tap.c
@@ -544,6 +544,7 @@ PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
* @dest: Destination port
* @saddr: Source address
* @daddr: Destination address
+ * @ttl: Time to live
* @msg: Array of messages that can be handled in a single call
*/
static struct tap4_l4_t {
@@ -555,6 +556,8 @@ static struct tap4_l4_t {
struct in_addr saddr;
struct in_addr daddr;
+ uint8_t ttl;
+
struct pool_l4_t p;
} tap4_l4[TAP_SEQS /* Arbitrary: TAP_MSGS in theory, so limit in users */];
@@ -776,6 +779,7 @@ resume:
(seq)->dest = (uh)->dest; \
(seq)->saddr.s_addr = (iph)->saddr; \
(seq)->daddr.s_addr = (iph)->daddr; \
+ (seq)->ttl = (iph)->ttl; \
} while (0)
if (seq && L4_MATCH(iph, uh, seq) && seq->p.count < UIO_MAXIOV)
@@ -824,7 +828,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET,
&seq->saddr, &seq->daddr,
- p, k, now);
+ seq->ttl, p, k, now);
}
}
@@ -1007,7 +1011,7 @@ append:
for (k = 0; k < p->count; )
k += udp_tap_handler(c, PIF_TAP, AF_INET6,
&seq->saddr, &seq->daddr,
- p, k, now);
+ DEFAULT_TTL, p, k, now);
}
}
diff --git a/udp.c b/udp.c
index 271e570..1ee289c 100644
--- a/udp.c
+++ b/udp.c
@@ -844,6 +844,7 @@ void udp_reply_sock_handler(const struct ctx *c, union epoll_ref ref,
* @af: Address family, AF_INET or AF_INET6
* @saddr: Source address
* @daddr: Destination address
+ * @ttl: TTL for packets to be sent in this call
* @p: Pool of UDP packets, with UDP headers
* @idx: Index of first packet to process
* @now: Current timestamp
@@ -854,7 +855,8 @@ void udp_reply_sock_handler(const struct ctx *c, union epoll_ref ref,
*/
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)
+ uint8_t ttl, const struct pool *p, int idx,
+ const struct timespec *now)
{
const struct flowside *toside;
struct mmsghdr mm[UIO_MAXIOV];
@@ -933,6 +935,12 @@ 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 <= 30) {
+ if (setsockopt(s, IPPROTO_IP, IP_TTL,
+ &ttl, sizeof(ttl)) < 0)
+ perror("setsockopt (IP_TTL)");
+ }
+
count++;
}
diff --git a/udp.h b/udp.h
index de2df6d..041fad4 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);
+ uint8_t ttl, 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);
--
@@ -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);
+ uint8_t ttl, 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
prev parent reply other threads:[~2025-03-15 15:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-15 15:32 [PATCH 0/2] udp: add guest-to-remote traceroute for IPv4 Jon Maloy
2025-03-15 15:32 ` [PATCH 1/2] udp: correct source address for ICMP messages Jon Maloy
2025-03-15 15:32 ` Jon Maloy [this message]
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