From 4ab5484a836529cf12fff69d5017f6aafc9dfcdc Mon Sep 17 00:00:00 2001 From: eugen Date: Wed, 18 Jul 2018 01:57:13 +0000 Subject: [PATCH] MFC r336195: unbreak dhclient(8) option 26 processing Make dhclient(8) verify if new MTU (option 26) differs from current one and skip unneeded MTU change. This check eliminates infinite loop of MTU change / link flap / lease verification / MTU change / link flap etc. in case of some NIC drivers like em(4) or igb(4). PR: 229432 Approved by: mav (mentor) --- sbin/dhclient/dispatch.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/sbin/dhclient/dispatch.c b/sbin/dhclient/dispatch.c index 176e91b1ab3..dcdc3c33f47 100644 --- a/sbin/dhclient/dispatch.c +++ b/sbin/dhclient/dispatch.c @@ -559,17 +559,29 @@ interface_set_mtu_priv(char *ifname, u_int16_t mtu) { struct ifreq ifr; int sock; + u_int16_t old_mtu; if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) error("Can't create socket"); memset(&ifr, 0, sizeof(ifr)); + old_mtu = 0; strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name)); - ifr.ifr_mtu = mtu; - if (ioctl(sock, SIOCSIFMTU, &ifr) == -1) - warning("SIOCSIFMTU failed (%d): %s", mtu, + if (ioctl(sock, SIOCGIFMTU, (caddr_t)&ifr) == -1) + warning("SIOCGIFMTU failed (%s): %s", ifname, strerror(errno)); + else + old_mtu = ifr.ifr_mtu; + + if (mtu != old_mtu) { + ifr.ifr_mtu = mtu; + + if (ioctl(sock, SIOCSIFMTU, &ifr) == -1) + warning("SIOCSIFMTU failed (%d): %s", mtu, + strerror(errno)); + } + close(sock); }