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Fix a memory leak when ip_output_send() returns EAGAIN due to send tag issues

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When ip_output_send() returns EAGAIN due to issues with send tags (route
change, lagg failover, etc), it must free the mbuf. This is because
ip_output_send() was written as a wrapper/replacement for a direct
call to  if_output(), and the contract with if_output() has
historically been that it owns the mbufs once called. When
ip_output_send() failed to free mbufs, it violated this assumption
and lead to leaked mbufs.

This was noticed when using NIC TLS in combination with hardware
rate-limited connections. When seeing lots of NIC output drops
triggered ratelimit send tag changes, we noticed we were leaking
ktls_sessions, send tags and mbufs. This was due ip_output_send()
leaking mbufs which held references to ktls_sessions, which in
turn held references to send tags.

Many thanks to jbh, rrs, hselasky and markj for their help in
debugging this.

Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D34054
Reviewed by: hselasky, jhb, rrs
MFC after: 2 weeks
This commit is contained in:
Andrew Gallatin 2022-01-27 10:28:15 -05:00
parent 38da0c96dc
commit 9ba117960e
2 changed files with 4 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
sys/netinet/ip_output.c
View File

@ -239,6 +239,7 @@ ip_output_send(struct inpcb *inp, struct ifnet *ifp, struct mbuf *m,
* packet.
*/
if (mst == NULL) {
m_freem(m);
error = EAGAIN;
goto done;
}
@ -263,6 +264,7 @@ ip_output_send(struct inpcb *inp, struct ifnet *ifp, struct mbuf *m,
KASSERT(m->m_pkthdr.rcvif == NULL,
("trying to add a send tag to a forwarded packet"));
if (mst->ifp != ifp) {
m_freem(m);
error = EAGAIN;
goto done;
}

2
sys/netinet6/ip6_output.c
View File

@ -336,6 +336,7 @@ ip6_output_send(struct inpcb *inp, struct ifnet *ifp, struct ifnet *origifp,
* packet.
*/
if (mst == NULL) {
m_freem(m);
error = EAGAIN;
goto done;
}
@ -360,6 +361,7 @@ ip6_output_send(struct inpcb *inp, struct ifnet *ifp, struct ifnet *origifp,
KASSERT(m->m_pkthdr.rcvif == NULL,
("trying to add a send tag to a forwarded packet"));
if (mst->ifp != ifp) {
m_freem(m);
error = EAGAIN;
goto done;
}