Rich Felker
114178dc8d
always try the time64 syscall first since we can use its success to conclude that no conversion is needed (any setsockopt for the timestamp options would have succeeded without need for fallbacks). otherwise, we have to remember the original controllen for each msghdr, requiring O(vlen) space, so vlen must be bounded. linux clamps it to IOV_MAX for sendmmsg only (not recvmmsg), but doing the same for recvmmsg is not unreasonable, especially since the limitation will only apply to old kernels. we could optimize to avoid trying SYS_recvmmsg_time64 first if all msghdrs have controllen zero, or support unlimited vlen by looping and emulating the timeout logic, but I'm not inclined to do complex and error-prone optimizations on a function that has so many underlying problems it should really never be used.
69 lines
1.7 KiB
C
69 lines
1.7 KiB
C
#include <sys/socket.h>
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#include <limits.h>
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#include <time.h>
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#include <sys/time.h>
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#include <string.h>
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#include "syscall.h"
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hidden void __convert_scm_timestamps(struct msghdr *, socklen_t);
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void __convert_scm_timestamps(struct msghdr *msg, socklen_t csize)
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{
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if (SCM_TIMESTAMP == SCM_TIMESTAMP_OLD) return;
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if (!msg->msg_control || !msg->msg_controllen) return;
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struct cmsghdr *cmsg, *last=0;
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long tmp;
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long long tvts[2];
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int type = 0;
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for (cmsg=CMSG_FIRSTHDR(msg); cmsg; cmsg=CMSG_NXTHDR(msg, cmsg)) {
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if (cmsg->cmsg_level==SOL_SOCKET) switch (cmsg->cmsg_type) {
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case SCM_TIMESTAMP_OLD:
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if (type) break;
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type = SCM_TIMESTAMP;
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goto common;
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case SCM_TIMESTAMPNS_OLD:
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type = SCM_TIMESTAMPNS;
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common:
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memcpy(&tmp, CMSG_DATA(cmsg), sizeof tmp);
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tvts[0] = tmp;
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memcpy(&tmp, CMSG_DATA(cmsg) + sizeof tmp, sizeof tmp);
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tvts[1] = tmp;
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break;
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}
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last = cmsg;
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}
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if (!last || !type) return;
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if (CMSG_SPACE(sizeof tvts) > csize-msg->msg_controllen) {
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msg->msg_flags |= MSG_CTRUNC;
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return;
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}
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msg->msg_controllen += CMSG_SPACE(sizeof tvts);
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cmsg = CMSG_NXTHDR(msg, last);
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cmsg->cmsg_level = SOL_SOCKET;
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cmsg->cmsg_type = type;
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cmsg->cmsg_len = CMSG_LEN(sizeof tvts);
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memcpy(CMSG_DATA(cmsg), &tvts, sizeof tvts);
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}
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ssize_t recvmsg(int fd, struct msghdr *msg, int flags)
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{
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ssize_t r;
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socklen_t orig_controllen = msg->msg_controllen;
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#if LONG_MAX > INT_MAX
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struct msghdr h, *orig = msg;
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if (msg) {
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h = *msg;
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h.__pad1 = h.__pad2 = 0;
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msg = &h;
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}
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#endif
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r = socketcall_cp(recvmsg, fd, msg, flags, 0, 0, 0);
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if (r >= 0) __convert_scm_timestamps(msg, orig_controllen);
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#if LONG_MAX > INT_MAX
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if (orig) *orig = h;
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#endif
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return r;
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}
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