Commit 2b440432 authored by Thomas Huth's avatar Thomas Huth Committed by Jan Kiszka

slirp: Fix packet expiration

The two new variables "arp_requested" and "expiration_date" in the mbuf
structure have been added after the variable-sized "m_dat_" array. The
variables have to be added before the m_dat_ array instead.
Without this patch, the expiration_date gets clobbered by code that
accesses the m_dat_ array.
I experienced this problem with the code in slirp/tftp.c: The
tftp_send_data() function created a new packet with the m_get()
function (which fills-in a default expiration_date value). Then the
TFTP code cleared the data section of the packet, which accidentially
also cleared the expiration_date. This zeroed expiration_date then
finally causes the packet to be discarded during if_start(), so that
TFTP packets were not transmitted anymore.

[Jan: added comment as suggested by Fabien ]

CC: Fabien Chouteau <>
Signed-off-by: default avatarThomas Huth <>
Signed-off-by: default avatarJan Kiszka <>
parent 8d06d69b
......@@ -82,12 +82,13 @@ struct m_hdr {
struct mbuf {
struct m_hdr m_hdr;
Slirp *slirp;
bool arp_requested;
uint64_t expiration_date;
/* start of dynamic buffer area, must be last element */
union M_dat {
char m_dat_[1]; /* ANSI don't like 0 sized arrays */
char *m_ext_;
} M_dat;
bool arp_requested;
uint64_t expiration_date;
#define m_next m_hdr.mh_next
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