Date: Fri, 28 Feb 2014 09:38:38 -0500 From: Robert Blayzor <rblayzor.bulk@inoc.net> To: freebsd-stable@freebsd.org Subject: [patch] bootp_subr.c support for jumbo frames on BOOTP intf Message-ID: <36E8D129-6D5B-4C69-834E-85D3F243B756@inoc.net>
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[-- Attachment #1 --] I am attaching a patch for those that wish to test or provide feedback. Currently there is no support for adjusting the MTU on an interface a diskless client boots from. Additionally if you attempt to adjust the MTU on the interface with ifconfig after the system comes up, the result is only cosmetic and the booting interface still cannot pass frames larger than 1500 bytes. There is a RFC standard DHCP TAG to provide a hit to a client what interface MTU should be set to. The attached patch will use this DHCP option in bootp and set the interface MTU accordingly. This allows diskless clients to be booted on a jumbo frame enabled network. Before using this, make sure your network and NIC is jumbo frame enabled/capable. Additionally the attached patch removes the client from setting itself as the gateway (proxy-arp) if there is no router provided from DHCP. The reasoning behind this is that it is more common for hosts to be multi-homed and that the booting interface may not necissarily be the interface a gateway is to be installed on. My erroneously setting gateway to hosts self, a default route cannot be easily changed at boot time. If the host needs to set itself as the gateway, return that in an option in DHCP. For tracking: PR: http://www.freebsd.org/cgi/query-pr.cgi?pr=misc/187094 (should probably be moved from misc to kern) Patch is against: 10.0-RELEASE r261846 -- Robert Blayzor Network Architect & Engineer CCIE 42148 (SP) rblayzor@inoc.net INOC, LLC 80 State Street, 7th Flr Albany, NY 12207 USA [-- Attachment #2 --] Index: sys/nfs/bootp_subr.c =================================================================== --- sys/nfs/bootp_subr.c (revision 261846) +++ sys/nfs/bootp_subr.c (working copy) @@ -196,6 +196,8 @@ #define TAG_HOSTNAME 12 /* Client host name */ #define TAG_ROOT 17 /* Root path */ +#define TAG_INTF_MTU 26 /* Interface MTU Size (RFC2132) */ + /* DHCP specific tags */ #define TAG_OVERLOAD 52 /* Option Overload */ #define TAG_MAXMSGSIZE 57 /* Maximum DHCP Message Size */ @@ -229,6 +231,8 @@ #endif static char bootp_cookie[128]; +static unsigned int bootp_ifmtu = 0; + static struct socket *bootp_so; SYSCTL_STRING(_kern, OID_AUTO, bootp_cookie, CTLFLAG_RD, bootp_cookie, 0, "Cookie (T134) supplied by bootp server"); @@ -1030,7 +1034,22 @@ return (0); } - printf("Adjusted interface %s\n", ifctx->ireq.ifr_name); + printf("Adjusted interface %s", ifctx->ireq.ifr_name); + + /* Do BOOTP interface options */ + if (bootp_ifmtu != 0) { + printf(" (MTU=%d", bootp_ifmtu); + if (bootp_ifmtu > 1514) + printf("/JUMBO"); + printf(")"); + + ifr->ifr_mtu = bootp_ifmtu; + error = ifioctl(bootp_so, SIOCSIFMTU, (caddr_t) ifr, td); + if (error != 0) + panic("%s: SIOCSIFMTU, error=%d", __func__, error); + } + printf("\n"); + /* * Do enough of ifconfig(8) so that the chosen interface * can talk to the servers. (just set the address) @@ -1053,7 +1072,12 @@ /* Add new default route */ - if (ifctx->gotgw != 0 || gctx->gotgw == 0) { + /* Only set default route if we received one in the request. + Proxy ARP considered obsolete. More valid to NOT set + a router in request as the host may be multi-homed and + gateway may not be on this interface. + */ + if (ifctx->gotgw != 0 || gctx->gotgw != 0) { clear_sinaddr(&defdst); clear_sinaddr(&defmask); /* XXX MRT just table 0 */ @@ -1518,6 +1542,11 @@ p[i] = '\0'; } + p = bootpc_tag(&gctx->tag, &ifctx->reply, ifctx->replylen, + TAG_INTF_MTU); + if (p != NULL) { + bootp_ifmtu = (((unsigned char)p[0] << 8) + (unsigned char)p[1]); + } printf("\n");
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